Inductor Voltage Calculations - Page 1
Forum section: electronics / beginners

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: June 13, 2017, 07:35:11 pm
content: This is probably a stupid question, but please bear with me, as this is all still theoretical to me.I'm making a boost inductor and I just wanted to make sure I'm calculating for the voltage correctly.EDIT: I forgot to mention that the input voltage is unfiltered(no filter cap), rectified mains voltage with a VPKranging from 100-340VDC @ 100-120Hz to output 400VDC. I will be using 2 boost inductors operating in opposite phase of each other to minimize output ripple and maximize power output. A sample voltage will be taken from the output and fed to a comparator in order to modify duty cycle as needed to maintain a smooth 400VDC output, ideally able to power a +/-1kW load (full bridge DC-DC conversion topology).Switching will begin @ zero crossing, where the MOSFET switching voltage will be gradually increased from VTHto 12V over a period of 200-250ms to keep current spikes to a minimum. Duty cycle will be limited to a maximum of 75%, switching at 100kHz. I'll be using 2 E42/21/15 PC40 ferrite cores where I may introduce an air gap at the center leg if absolutely necessary(I'd prefer not to due to fringing).Is the equation:N =Vx1044fAeBOr does that only apply to transformer windings(i.e. mutual inductance)?If it does apply to inductors, should V = Vboostor rectified, unfiltered, 100-120Hz Vin?

author: Paul Price
author_rank: Super Contributor
timestamp: June 13, 2017, 07:50:47 pm
content: Got a detailed breakdown of your formula or a circuit/schematic to apply your formula to?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 13, 2017, 08:22:47 pm
content: Ew, cgs units...Anyway, V is the square wave peak voltage. The 'input' side of the inductor is held constant at +V, and the other side is pulled down to 0V then clamped at 2*(+V) (for a 50% duty cycle).Note that V / f has units of flux (volt*sec). The 1/4th is because flux rises and falls, averaging zero, throughout the square wave.This further assumes that DC current is zero, because if DC current were nonzero, flux would be nonzero (inductance is the conversion factor between flux and amps -- just as resistance is the conversion factor between volts and amps; and both obey Ohm's law, as long as they are linear components).A boost converter obviously does not have zero DC, so the equation needs to be modified.If you are in DCM (discontinuous current mode: inductor current returns to zero after the flyback pulse, and before the switch turns on again), then change the factor of 4 to 2. (Flux doesn't average zero, but it returns to zero, so you're using the positive half of the total available flux.)But it would be more appropriate to work from another equation directly. Understand that flux is:Phi = V/f = V*sand when you are applying a constant voltage to an inductor, you are applying a flux over time. That flux is simply the applied voltage times the pulse width.But even better would be to not work with flux at all. Your peak current mode converter should only turn on until the inductor current reaches a critical value, then turns off. This prevents the current build-up that is the curse of a voltage-mode (i.e., feeding fixed PWM into an inductor) controller. The circuit is just as simple, yet you obtain short circuit protection and power limiting for free! (Reference: UC3842.)In that case, you use the inductor equation:V = L * dI/dtdI is the rise in current during the pulse, and dt is the pulse length.You only need to work with B (flux density) when selecting and gapping a core, and to check that you're not saturating it.Tim

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: June 13, 2017, 10:20:14 pm
content: I've provided a bit more detail on the project. Based on your answer, I think you were under the assumption that I was building a normal boost converter.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 14, 2017, 12:31:21 am
content: Well, that hasn't changed anything, you still are...Also, it's better to add information in a reply, otherwise it breaks thread order.Some errors:Quote from: hanzdolo30@gmail.com on June 13, 2017, 07:35:11 pmNo -- once the MOSFET cooks off, current will spike once, massively, and whatever protective device is in place (hopefully a fuse, else the breaker) opens.This is not how you reduce current spikes -- you control current bycontrolling current!Always make sure the MOSFET is switching sharply, otherwise it will get very hot, very quickly.Turn on the transistor until it's carrying the current you need, then turn it off. Simple as that. BCM PFC controllers exist, which handle this for you -- example:http://www.onsemi.com/pub/Collateral/NCP1608-D.PDFNote the resistor in series with the MOSFET source, sensing current. You must do this first -- turn on the switch until the current reaches a threshold, then turn it off, and repeat after some time.The result will be PWM, but PWM is not the goal, it is the side effect of controlling current.You'd use a different controller, like UCC28010 or whatever, to handle the biphase timing and stuff, and also to get better efficiency at 1kW.Also, 1kW is quite a lot of power -- please do build (or purchase a demo board) a lower power level one first!QuoteOther error -- the air gap is were energy is stored, so the coremustbe gapped -- or, if not, it must be about a hundred times larger, which is ridiculous.You can also get core materials with a low permeability, that do not need an external gap.You are quite correct that fringing fields are dangerous -- you'll need to use Litz wire here.To use cheaper (but also much bigger) inductors, you'll need to consider a CCM controller, which has added complexity over the simple BCM type PFC controllers. These are not general-purpose parts, so you're better off following the manufacturer's recommended design.Tim

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: June 14, 2017, 01:31:03 pm
content: Quote from: T3sl4co1l on June 14, 2017, 12:31:21 amI'm not arguing the point, because you are obviously well versed on the topic, where this is my first high voltage application of a boost converter. I just want to make sure you're understanding me as well as me obtaining a better understanding of the magnetics of the circuit. I really appreciate the time taken to assist me.I was referring to gradually increasing the pulse voltage from VTH(about 4.5V) to 12V, over a period of 200ms, not just linearly increasing the voltage at the gate. I'm aware that would desolder the MOSFET or worse(I've had it happen before). The circuit as described seems to work in well in simulation. In LTSpice I saw a gradual increase in current when I did that, otherwise I saw an 80Aspike when I started it up at 12V. Due to a lack of available IC models, I used an NE555 with a whole lot of auxiliary circuitry(what a headache that was), the PWM being controlled by the comparator via the CV pin. In that simulation I had the VBOOSTEDattached to a 129 ohm load resistor.I've built boost converters for low voltage applications that operated at 200W attached to the 12V rail of an ATX PSU (Good Corsair 1000W supply), using a BJT astable, without tripping the PSU's protection circuitry. I was using a toroid with some litz wire that I made using some 30AWG magnet wire I had lying around. The operating frequency was at about 150kHz (I'm sure you know BJT astables aren't the most reliable oscillators).QuoteI have a variety of PFC and offline SMPS controllers from Fairchild (Now On-Semi), but I thought it was a lot of fun using the NE555s for something that they are totally not designed for.QuoteI'm aware of the existence of distributed gap cores and skin effect. I actually got that equation from a powder core manufacturer as a calculation for inductors, I noticed it was too much like the transformer winding equation, so I had to ask someone more knowledgeable on the topic.I just wanted to use what I have on-hand. I figured I could just calculate for BMAXto avoid core saturation.While I was testing the LCR meter I just got, I noticed the gap doesn't have to be very big to cause a dramatic drop in inductance/increase in reluctance.I'm currently reading "Transformer and Inductor Design Handbook", so I do know all of the equations for gapping the core and increasing reluctance (RM). It seems, adding a gap to an MMF circuit is equal to using a resistor in an EMF circuit, it's just that fringing that I'm worried about.

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: June 15, 2017, 01:41:02 am
content: Quote from: T3sl4co1l on June 13, 2017, 08:22:47 pmI just wrapped my head around the math, Faraday's equation. It's so simple I missed it the first time around. I guess I will have to gap the core (I wouldn't want an inductor the size of my kitchen table), which is a little tricky because it's pretty difficult to sand a mm of core down perfectly, let alone two equally, Yikes!I may just shell out a couple bucks for a pair of Cool mu toroids. It's probably not worth the hassle just to end up with 2 totally dissimilar inductors.Thanks again.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 15, 2017, 03:30:23 am
content: Quote from: hanzdolo30@gmail.com on June 14, 2017, 01:31:03 pmI understood correctly, then.Understand what you are doing:By reducing Vgs(on), you are reducing the switching capacity of the MOSFET. That is, it turns on, and pulls the voltage down, then the voltage goes back up, while it's still on. The transistor is sinking, say, a few amperes, at full supply voltage, thus dissipating hundreds or thousands of watts!A simulation will show this working just fine, but so too, it will show the "80A inrush" version working just fine. There's no smoke in SPICE.It's your responsibility, as the creator of the model, to make it representative of the thing you actually want to build -- to "model" it!QuoteGosh... You should familiarize yourself with more basic building blocks!In SPICE, there are ideal everythings!It is, in turn, your responsibility to use these carefully -- as ideal elements, they don't have limited bandwidth, or time delay, or bounded output ranges. You need to put those aspects in, yourself.But, that said: controlled sources allow you to amplify, scale, isolate, and put functions on any voltage or current, or combination thereof, you like. This is Turing complete (on the condition that memory -- state -- is limited by size of the circuit, which can't be modified during runtime), so you can truly build anything!A good replacement for a 555 is a couple flip-flops or gates, comparators, a switch and a buffer. Comparators convert analog to digital, and you then use the digital signal with logic gates. (There is a distinction between analog and digital, in SPICE: XSPICE and other extensions provide a true event-driven digital logic simulation, which has to be interfaced with the analog side with converters. The converters are usually implicit, but be mindful that they exist -- sometimes they screw up!https://www.seventransistorlabs.com/Images/AltiumDigGlitch.png)Comparators: recommend using a proper model like LM339 (mind the open collector output) or whatever (driven logic output) type is equivalent or better.Switches: use transistors. There is a SPICE switch, but they can be unstable (they're implemented by an ideal dependent resistance and nothing else, so can behave very unrealistically), and a transistor will capture real limitations like finite gain, bounded voltage and current, and speed.Simple logic functions can also be done with transistors. AoE2 called this "Mickey Mouse logic" (in the context of glue logic when you happen to need a couple transistors' worth), but it's easily tossed to the corner of a schematic sheet in SPICE.Everything else, current sources, ramp generators, that sort of thing: use capacitors, resistors, inductors, transistors, sources, whatever works.Nice thing about PFC in SPICE: you can make the multiplier and divider section trivial and perfect, no faffing about with PWM conversion or ADC-MDAC or analog multiplier sections!QuoteBJTs are better than they're given credit for, but they aren't as "logical" as MOSFETs -- namely, you need to drive them with the right combination of voltage and current, and that it takes more current (the base input impedance is simply lower), whereas driving a MOSFET requires little more than a big fat logic buffer.Tim

author: jbb
author_rank: Super Contributor
timestamp: June 15, 2017, 08:01:31 am
content: Quote from: hanzdolo30@gmail.com on June 15, 2017, 01:41:02 amOh yes, trying to work ferrite is horrible. However, there are 2 options you could look at: firstly, can you buy a pre-gapped core set? Secondly, remember that (for e.g. an E core) you can just gap all three legs. It's not quite ideal but very many power electronics prototypes are made this way.On Kool Mu: remember to look at the loss density vs. frequency. Kool Mu may be too lossy at high frequency.On Vgs supply: T3sl4co1l is dead right. Use of low Vgs supply is the wrong solution to your problem and greatly increases the risk of blowing MOSFETs.Quote from: Paul Price on June 13, 2017, 07:50:47 pmMaybe with a schematic (e.g. from LTSpice) someone could help you work out why the inrush is happening and suggest a remedy.For example: you're building a two-phase interleaved boost PFC rectifier. Boost PFC rectifiers are known to have a large inrush current when AC power is first applied because the bulk DC capacitor starts off empty. This has nothing to do with the switching MOSFETs.

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: June 21, 2017, 02:02:56 am
content: Quote from: T3sl4co1l on June 15, 2017, 03:30:23 amFor me this is one of those situations where the more you learn, the more you realize you don't know.I was actually ill advised by someone on stackexchange. Thank you for the correction.I thought he was correct, being the MOSFET wasn't on for the entire time period it could handle the pulses of current, gradually charging the inductor over 1/5 of a second rather than just hard switching at the full 12V. However now that I've actually done the calculations since reading your reply, the heat dissipation would probably cause the MOSFET to explode violently.My original idea was to engineer a soft start by gradually increasing positive pulse width (which I think a youtube I saw video recently confirmed) until the VBOOSTEDarrived at the peak voltage of 400V, then the comparator would modify the duty cycle to keep it at that point. That's actually a simplified rundown because it doesn't just increase the duty cycle like that. There's a bit of transistor logic and RC timing incorporated into that circuit. Once I've removed that bad advice from the original schematic, I'll post it.Would you say that's a step in the right direction?QuoteOh, I'm aware that LTSpice will allow a 2N2222 to operate at 1000V with 50A going through it with no problem.For instance I designed a simple phase shift oscillator in SPICE that worked like a charm, but on the breadboard I had to add 3 more resistor, capacitor stages then it actually worked, I even added a schmitt trigger and made a square wave output with a variable duty cycle. SPICE was wrong about the oscillating frequency as well. In fact SPICE let me put just about any resistor or capacitor values in and still worked.I took a look at that link and Yikes!I am pretty familiar with basic circuit building blocks. It's magnetics that I've been having issues with, but I seem to be getting the equations under control. Such as, air gaps, Fringe Flux Factor, etc.. I see an air gap is absolutely necessary to maintain a proper B-H curve.I'm actually waiting on UPS to deliver some LM339s among others, as I'm writing this.QuoteI totally agree. However when I post a schematic with a bunch of BJTs in it, I get people telling me that the schematic is convoluted and I should just use ICs. If I can't find an IC that does exactly what I want and IC's will almost always take up more space in my case (simple logic gates, etc. and I don't have the many of the requirements for surface mount components), so why not use BJTs? I'm using breadboards(never for power conversion) and perfboard.I actually enjoy working with BJTs. They're quite logical as long as their operating parameters are understood, Q-point, saturation point, etc.. It's kinda like coding in hardware(I'm a programmer), lol .I was referring to the astable multivibrator circuit itself being a bit difficult to use as far as implementing a voltage controlled duty cycle. It seems I would have to use current sources which can be a bit imprecise from BJT to BJT of the same value due to things as simple as ambient temperature and a number of other factors (of course in SPICE everything is peaches).The boost converter I made worked great, it's just that I would have liked to have better control over the output current with load detection rather than using a trim-pot to manually compensate. You know once it sees a voltage drop below the the 60V, increase duty cycle, but limited it to no more than 70% on time. I believe that's the point where ICs become absolutely necessary.

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: June 21, 2017, 03:11:19 am
content: Quote from: jbb on June 15, 2017, 08:01:31 amI just got a digital caliper and a set of diamond grit files, so I may be able to get away with grinding down the center legs. I just have to calculate the lg, and hope I don't shave off too much.QuoteI'll post a schematic once I remove thebad advicethat was given to me from the schematic. I think I may have been confused as to what a soft start really is. I was put under the impression that it was a gradual voltage increase, where on youtube I saw a soft start on someone's oscilloscope and seemed to be a gradual increase in duty cycle. It was one of those terrible videos with no explanation, but I think it was pretty obvious.I think the reason I saw an insane amount of inrush current is because I had a 129resistor attached as a load from startup.In the actual circuit that wouldn't be the case. There would be no load but a small flyback that will be used to power the primary circuit and even that wouldn't start switching until the PFC stage reached it's peak voltage of 400V. Once the flyback has has reached it's peak voltage, then the main full bridge transformer would begin switching to power the actual 1kW load, where each switching cycle would begin at zero crossing.Does that sound about right?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 21, 2017, 04:11:40 am
content: Quote from: hanzdolo30@gmail.com on June 21, 2017, 02:02:56 amExcellent! Once you begin to get a flavor for how little you might actually know, you can begin to fill in those gaps, however small a piece at a time.QuoteYes. But more to the point: what are youreallycontrolling?If you're charging an inductor, and when the charge (current) gets too high the transistor blows up...... why not just stop charging when it's "full"?In other words, measure the switch current, and turn off the switch when it reaches some peak value.The circuit is an RS flip-flop connected to the transistor (with gate driver). An oscillator periodically pokes S, turning on the transistor. A comparator monitors current, relative to a threshold, and hits R when triggered.Even if the inductor current stays high between pulses, the transistor will never stay on longer than the propagation delay of the comparator, f/f, driver and switch. Which can be on the order of 100ns, nowhere near enough time to destroy the transistor (at least, from just one hit).Bonus: as you vary threshold voltage, the peak current, and therefore output power, varies proportionally. Well isn't that handy?Suppose you control it so that input current is proportional to input voltage -- now you have your basic PFC!(There are some added tricks to realize a full PFC: you need an outer voltage feedback loop, which varies the gain of the inner current loop, gradually (a time constant of several line cycles), so the output voltage can be stabilized without interfering with the ripple that the PFC section has to create. Feedforward compensation is normally used as well, to keep the loop stable over wide changes in input voltage.)QuoteHmm, well -- depends. SPICE is capable of modeling breakdown voltage (though not the latching avalanche breakdown that can occur in BJTs), and the hFE reduction at high current.Not all models are made equally. And cheap or shitty parts tend to have shitty models. Nevermind that they've made, I don't know, a billion dollars worth of that part over the last half a century.QuoteYou say "worked like a charm", I say "didn't model reality worth diddly squat".It's ultimately your responsibility to verify the models you put into your simulations, that they behave reasonably, and that your whole simulation is realistic.You can easily build a bunch of chaotic nonsense with dependent sources, but that doesn't make it real.Here's another model:The left side is what I built. It happens to be an oscillator! Q4 collector voltage wiggles around maybe 0.5V at 30MHz (pretty fast for a TIP31, huh?). (Oh FYI, MJD31C is the SMT version of TIP31C, and C is just the voltage grade in the TIP31 family. Pretty much same things electrically, other than that.)The right hand stuff is what I had to do to the circuit to make it "behave". The inductances and capacitances correspond to lead inductances and device capacitances; except that, the inductances are far too large to be representative (by about 5 times), and the model already has capacitance parameters in it, so I shouldn't need to add more outside!I suspect the problem is a transport (charge diffusion) effect inside the TIP31, causing real delay or something like that, which is enough to shift the poles into the right half plane. SPICE doesn't do this. Notoriously, SPICE has no support of transport phenomena, besides one-dimensional transmission lines, which are something of a hack anyway. Instead, SPICE represents charge as a dependent capacitor. But a capacitor can be discharged instantly, and has no delay (it adds a derivative, but not a time displacement), while a junction cannot.Other times, I've had overly optimistic results: this amplifierhttps://www.seventransistorlabs.com/Images/WidebandAmp.pngshowed 300MHz bandwidth (-3dB) in SPICE, albeit with no particular attempt at replicating real parasitics (likely, trace capacitance is a pF or two on most nodes, resulting in not quite half the bandwidth). The real one measures 100MHz, though.IIRC, noise did come out okay though. (The figure shown is measured.)QuoteHaters to the left...To be fair, drawing everything out, discrete, is tedious and not very productive. I might explore a circuit that way, or breadboard it, but where simple functions are needed (amps, comparators, logic), I always reach for ICs when it's time to implement it for real.Tim

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: June 21, 2017, 08:24:08 am
content: Quote from: T3sl4co1l on June 21, 2017, 04:11:40 amYes I've noticed, that's usually the case, lol.QuoteNow that's where I get a little confused. Because I thought that by feeding back a reference voltage from the boosted output to the comparator and dropping the CV pin of the NE555s to 0V, stopping oscillation did exactly as you described. No charging unless output voltage drops below 400v, then it starts back up again. At least it seems logical. However I've only done high voltage boost in simulation where as you describe it, sounds a lot safer and you've obviously done this before.QuoteI actually got the original schematic from a working example on youtube, using all of the same component values and for some reason it still didn't work in real life, until I added those 3 stages.I've made my share of chaotic nonsense in spice that I tried to manifest in reality. I have a charbroiled breadboard that I keep around to remind me to make sure my calculations are on point.I also have a BJT astable that I blew up, as a constant reminder that earth groundIS NOTthe same as the 0V at the rectifier.Ground is a reference point never to be confused.QuoteNow that I actually know how to use them, I usually just use the BJTs for simple amplification where an Op-Amp would be overkill, driving MOSFETs, simple logic gates and switching parts of the circuit on or off based on reference voltages. These guys I'm talking about always want to see acanned productin use for damned near everything. For me at this point, it's more about the learning experience. Anybody can follow directions on a datasheet. The old school guys can usually appreciate the use of BJTs in conjunction with IC's. I also use them in simulation for the sake of making the simulations run faster. When I add an IC model to a schematic, the SG3525 for example, which I have Fairchilds version of, and plan to really use with the Hi/Low side drivers, it really slows things down tremendously. It's faster when I put together a crazy circuit with NE555s (insert deadtime) and a charge pump in SPICE rather than use the IC models, which perplexes me. Though the IC models of the SG3525 and driver ICs come from weird places and the NE555 is native to LT.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 21, 2017, 08:52:49 am
content: Quote from: hanzdolo30@gmail.com on June 21, 2017, 08:24:08 amOutput voltage != switch current!That's a hysteretic converter, which is no better than MC34063 (which is similarly in my class of "people use it because they don't know better" parts), and completely unlimited on switch current. They're typically bad at ripple, and depend on stable capacitor ESR.Tim

author: MrAl
author_rank: Super Contributor
timestamp: June 21, 2017, 11:20:07 am
content: Quote from: hanzdolo30@gmail.com on June 13, 2017, 07:35:11 pmHi,To add a little here, that voltage is the voltage across the inductor winding. It's the same for a transformer primary. That "4" in the denominator tells us it is the formula that considers the drive wave shape to be rectangular, not sinusoidal. If you see "4.44" instead that is for sine waves.Also, a gap basically just reduces the total construction permeability so that the core does not saturate with the expected operating current. Since many magnetic materials used for these applications have roughly the same saturation flux density spec and the drive current needs to be at a certain level in order to satisfy the application requirements, when we add a gap we effectively raise the level of current we can get away with in a given application. However, since lowering the permeability is the main goal (higher current before we reach saturation) we can simply use a lower permeability core. Creating a precision gap requires some decent machinery so if we use a lower permeability core we might get away without needing a gap. Of course the overall inductance lowers, but since the inductance decreases in proportion to the permeability and the inductance increases with the square of the turns ratio, when we add more turns to compensate we end up with the same inductance but with a higher saturation current level. With a low mu core we might be able to reach our goal without needing a gap.In spite of this information it is still better to purchase an inductor that fits the bill. There are a lot of inductors out there for sale that might work in this application and they are fully spec'd so you can pick and choose just what you want. That is the most sure way to get this up and running in the least amount of time. You can always go back and try to recreate the purchased inductor later if you need it for some production run or something.

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: June 21, 2017, 07:11:44 pm
content: Quote from: T3sl4co1l on June 21, 2017, 08:52:49 amThat completely makes sense, because(correct me if I'm wrong here)with a hysteretic converter, if the load begins to draw more current than the source can supply, it can still result in core saturation and too much current going through the MOSFET anyway (FET goes BOOM!). However if the actual current is being monitored as well as the output voltage(giving switch current priority over output voltage of course), we end up with a PFC stage that won't have the potential of an exploding MOSFET or worse.

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: June 21, 2017, 08:07:28 pm
content: Quote from: MrAl on June 21, 2017, 11:20:07 amSince the Initial post, I've acquired quite a bit of knowledge on the topic, realizing that there are a number of factors involved in building an inductor core (too many equations to write down here without mathjax). Just to name a few, there's calculating the appropriate gap size for the application, BMAX, N (being exactly as you've described it), fringe flux factor, etc..Theres one thing that I still haven't figured out, that the books don't explain. Where does that factor of 4 for square waves or 4.44 in the denominator for sine waves come from?Does it have to do with the angle of the wave form? I was guessing it did until a few people on other forums told me to use a factor of 2, which totally confused me.At this point, I'd prefer not to use a"canned"product, because I feel it would not aid me in the learning process. I'm learning as much I can about electrodynamics and, I find magnetic theory particularly fascinating.I very much appreciate the time taken to assist me. Thank you!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 22, 2017, 01:02:46 am
content: Quote from: hanzdolo30@gmail.com on June 21, 2017, 07:11:44 pmPrecisely, current must take priority in all [switched inductor] converters. Ultimately, whatever you are doing, you have an inverter or switch, driving current through an inductor, and that current is the state variable of the inductor. It's what it does, period. Applying voltage causes a change in current, but only a change, it doesn't set the absolute value. So the inductor current is independent of the applied voltage (and consequently, PWM% or whatever). Then, the inductor current drives a change in voltage elsewhere (usually across a filter capacitor and load resistance), a second state variable.Once you recognize the state variables, and wrap controllers around each one, you can easily design an indestructible converter with nearly the best possible dynamics. You can't exceed switch/inductor current, because the current setpoint simply can't be commanded higher than whatever its input is designed to saturate at. (You can make a variable current limit supply by clamping the setpoint current to an adjustable voltage!) The inner current loop is easily compensated because it's a single pole, and the same is true of the outer voltage loop (given that the capacitor time constant is made longer than the current loop time constant, so that the poles don't interact much*).*The boundary condition would be if you can adjust it so the poles interact just the right amount, giving a 3rd or 4th order, say, Bessel or Butterworth filter response: whichever condition is optimal for the application.Tim

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: June 22, 2017, 06:27:05 am
content: Quote from: T3sl4co1l on June 22, 2017, 01:02:46 amTim, YOU ARE THE MAN!,Thank you for getting me through that issue and teaching me how to make my converters "bulletproof"You've actually inadvertently answered a few questions I had in mind. Using my imagination, I can see a few situations where those methods can be applied. Thanks to you, I'm gonna make some KICKASS converters!I don't even really need canned control IC's, I can do it all with Op-Amps and proper comparators (of which I have plenty), using some simple analog control logic.I have a bunch of silicon carbide semiconductors that I'd love to put into use, which is why I was talking kilowatt converters at the beginning.I'll show you the schematic once I've totally revamped it, being I've been doing it almost, all wrong.Though, I'd probably want to incorporate an MCU later on, so I can come up with some advanced control schemes. I think I told you before, I'm a programmer so that's right up my alley.Thanks again Tim.Gilbert

author: jbb
author_rank: Super Contributor
timestamp: June 22, 2017, 10:04:11 am
content: Unfortunately YouTube isn't a good source for power electronics. There's not a lot of explanation of circuit operation, and unfortunately they tend to be complex.And a PFC circuit isn't a gentle introduction to the field, either.Now that you've worked out why the power stage is going bang with inrush, you can move on to new and exciting ways to go bang.One software suggestion: keep an eye on the DC output voltage. If it goes significantly above your target voltage, the converter should cease operation (I.e. turn MOSFETs off) and not restart until you command it.Might I make some suggestions for safety:- make sure you have galvanic isolation between the power stage and yourself or any PC/laptop- add a drain resistor to the DC link cap to make sure it will eventually discharge- I suggest you place a transparent lid over the converter so you don't accidentally touch anything- try to set up all your test leads before turning on the main power, and not move them while power is applied- eye protection can be good. MOSFETs and diodes can explode into sharp fragments.

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: June 22, 2017, 03:31:12 pm
content: Quote from: jbb on June 22, 2017, 10:04:11 amYeah, I know. There's this one video where a guy was telling people to make boost converters with an esaki oscillator. That had to be one of the most dangerous things I've ever seen..No let me correct that.There was that one video where a guy made a step up push-pull alternator using an astable multivibrator to power a stereo system, like it was a great idea!.There are a lot of videos on youtube that teach the uninformed how to commit suicide. There are also the videos that'll show you a topology and give you no detail as to how to implement it.I've learned that it's best to watch the video and do further research on the topic. I tend to avoid anything that doesn't provide detailed formulae.There are a few good channels like iLecture Online (he provides detailed formulae on everything, which can be tedious, but you'll have a full understanding of anything he teaches) , The Post apocalyptic Inventor (started a great SMPS video series, with all of the math, but never finished it), EEVblog of course (which is how I ended up here) and Afrotech Mods (great for the basics), just to name a few.QuoteThis isn't exactly my first rodeo. Aside from some low voltage projects with MCUs (Not arduinos, I hate canned food,), I have made boost converters, charge pumps, isolated step up converters (30V max), using ATX PSU's as a source, so I actually did start out with a general understanding of the process. However, I've noticed that when working with mains power, there is very little margin for error before you end up with fireworks going off on your workbench.QuoteThat load resistor was just a dumb ass move on my part. Which is why coffee is absolutely not a good replacement for a well rested mind. As I was reading your comment on the inrush, I thought about the circuit and realizedT3sl4co1lhelped me work through the current measurement so hopefully there won't be anymore BANGs!QuoteI actually have a comparator taking care of that. Once the voltage arrives at 400V it pulls the CV pin on the NE555s down to 0V, essentially shutting the MOSFETs off. However, it seems the current across the FET is really the deciding factor. As I may see a voltage drop below my target voltage, the current can still be excessive, if the load device draws too much for some reason.I'm not sure I like the software, it lies to you. All of the successful projects I've had, were prior to using simulation software. Perhaps the late Bob Peas was correct when he said "I program in solder!", but like you said PFC isn't gentle.QuoteThat list of safety measures I should probably print in BIG BOLD letters and tape them to the wall above my workbench, lol.Thanks for that.

author: jbb
author_rank: Super Contributor
timestamp: June 23, 2017, 06:22:28 am
content: Remembered another safety suggestion: attach a multimeter to the main DC cap at all times. That way it won't lie in wait, charged and dangerous!

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: June 24, 2017, 01:31:33 am
content: Quote from: jbb on June 23, 2017, 06:22:28 amI usually use an indicator LED on a high value resistor to let me know when the circuit goes completely dead, but that's a good idea!Thanks for that!

author: MrAl
author_rank: Super Contributor
timestamp: June 24, 2017, 11:38:00 am
content: Quote from: hanzdolo30@gmail.com on June 21, 2017, 08:07:28 pmHello again,The factor 4.44 comes from sqrt(2)*pi. This comes out after starting with the equation for flux using sine waves. I'd really have to look up the derivation at this point as it's been a long time for me now since i did that, but this 4.44 appears in many magnetic handbooks also including the literature from the old Magnetics Inc. company.As n harmonics are added to this sine wave on the way to a square wave (each with amplitude 1/n) the core will saturate a little more easily with a given voltage, which means the flux density must go up with a square wave of equal amplitude. If all the significant harmonics are considered, the flux density goes up by approximately 4.44/4 so the factor in the denominator changes to 4. This is also in the Magnetics Inc. literature.https://www.mag-inc.com/

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: June 25, 2017, 10:31:19 am
content: Quote from: MrAl on June 24, 2017, 11:38:00 amThank you for that. I wish the books would just explain things like that, instead of giving me a number factor that I have no idea where it comes from.I've only been learning EE, summed up, for about 4 months. I took a very long break after frying a 4K monitor that was plugged in on the same power strip as a circuit with an improperly designed flyback converter that blew up like fireworks, because LTSpice said it would work. Which is why I'm very careful about calculating my magnetics.Non-magnetic magnetic passive components, semiconductors and ICs are simple and logical. I can use them with great proficiency, both in simulation and on the breadboard/circuit board, but when it comes to magnetics. Those handbooks can be really confusing. For instance, I learned that u0= 4*pi^-7, then this one stupid book tells me it's unity (u0=1) which totally threw me off,, and they put the actual u0in a weird format; lg= 0.4*pi*N*I^-8/BDC, which I didn't even catch on to until I found a good book where everything is in SI units, and u0is used in place of 0.4*pi^-8. In those handbooks they use strange variable names and values all the time. It's so annoying. Where's the consistency? Should I be studying physics instead? In the physics of it, there seems to be no inconsistencies, no matter the source. They just seem to take the long route about everything and I'm not designing core materials (for now), I just want to make a pair of inductors quickly, using stuff I already have on hand, that will definitely work.Sorry about the rant, it's just that I would have probably had the equations worked out in a day if it hadn't been for all of the inconsistencies, and one book lacking in something that the other didn't. It's so irritating.Can you recommend a book or a few?I have 3 questions that I hope you don't mind answering.1.The book doesn't go into detail about varying input voltages and inductance. When I calculate for the inductance of a PFC boost inductor, should I be calculating for the highest possible input voltage, VRMS*sqrt(2), (my guess is yes, but you'd know better)?2.Rather than calculating for fringe flux factor, couldn't I just avoid it entirely by calculating for the radius of the flux (it being proportional to lg), and put a few layers of teflon over the lgregion of the bobbin or perhaps the entire bobbin length for the sake of even winding?3.This question is about the MOSFETS and output voltage. I understand that the higher the output voltage, the lower your transformer current will be at a given power output, reducing the risk of saturation(correct me if I'm wrong). If you were building the converter to operate with a POUT>= 1kW and you had FCH023N65S3L4(same as next, 4 legs, 1-Drain 2-Power Source, 3-Kelvin Source, 4-Gate), FCH023N65S3_F155(650V, 75A, 23 m), FCH060N80_F155(800V, 58A, 60m), SCT30N120(1200V, 45A, 90 mSiC), MOSFETS and FFSH40120ADN_F155 (1200V 40A SiC), FFSH30120ADN_F155(1200V 30A SiC) Schottky rectifier diodes.What would be the ideal output voltage for the PFC application and which of the aforementioned components would you use at the chosen voltage, using a EE55/55/21, PC40 transformer core in a full bridge topology?Thank you for your time and patience.

author: MrAl
author_rank: Super Contributor
timestamp: June 25, 2017, 08:03:24 pm
content: Hi,I can help a little here.First, inductance books vary quite a bit as you found out. They dont all use the same units either, and because of that nagging 4*pi*10^=7 factor sometimes they dont even include any of that and work in some other units and other times they just use u0, and still other times they use u/u0 for when they want to include relative permeability, and that's just the start of things to go wrong :-)The best bet to combat the above and similar is to home in on a formula you like and try to find another one even if in different units, so you can compare results. Ideally, the results should come out identical within several decimal places, and even better as the ratio of two integers when possible. If they come out close but not exact, then you might be ok but you're better off trying to find out why there is a variation even if small, and possibly by simply trying some other parameter values. This allows you to be more sure of the result you need.The worst part about this is that when they hand you numbers and formulas they dont always show the derivation and sometimes that is because it is very long and complicated and takes some mathematical tricks to get an answer. Without that derivation though you have no idea what is going on, so it makes you feel kind of lost.What you could do is either find a better book or start to do some derivations of your own. To that end, you can start with the Biot Savart Law. That's the basic law behind a lot of magnetic calculations that can come out exact. There is always the practicality of it all though, which really makes everything we do outside of pure theory just an approximation, but at least then you can figure out why.To compute inductance behavior in a converter you have to know the voltage across it for all times, at least the maximum, and the expected maximum 'on' time. If you know those two you can get pretty far because an important aspect of that is in terms of volt seconds. In short, if you have more volt seconds than your winding can handle, it saturates.The max sometimes comes from normal operating conditions but if you dont have a slow start mechanism in place then you end up with more volt seconds than you expected, so you really need a slow start mechanism for any reasonably sized converter.If you vary the input voltage you need to consider the maximum input voltage and it's relation to the output voltage when the inductor topology puts it in series with the input and output. But again, this will bring in some form of slow start so the volt seconds can be limited during start up.You can estimate the fringe flux if you want too, and there are several articles online. Here is one i found:http://www.encyclopedia-magnetica.com/doku.php/flux_fringingThere may be more information on that Magnetics Inc site too.BTW you can always measure the characteristics of your inductor, and change the gap as needed during that test.The 'risk' of saturation...If you design it right you should not encounter this problem, right? Or did you find something that became a problem?If your inductor volt seconds are limited, it will not saturate. It's not really about current except when there is a DC current present as well as any AC. When there is DC also present, then yes, the DC could cause saturation, but that's something you include in the calculations for the inductance. Overloading must be avoided by current monitoring, if an overload of some type is expected, which is almost always a consideration.Not sure what you are asking about the MOSFETs here, but if you are doing a full bridge then the voltage ratings of each transistor must be higher than the expected max voltage across each transistor. It's that simple. Of course if you have significant spikes then you need to snub them, and possibly go up on the transistor rating.If you intend to output say 100v peak to the primary, then you should expect 100v peak, then add some head room for spikes and use snubbers. When a lower transistor turns on it's about 0v, but when the diode conducts it could be -2v, and when an upper turns on it's going to put 100v peak on one transformer lead, so you can figure maybe 102v if you like to be more accurate, but really we'd have to model this to get batter estimates. So you see using 120v MOSFET's would probably do the job unless we had significant spikes, and then maybe we would go up a little and improve the snubber.After all is said and done however, the unit must be tested. This comes from input a DC voltage (or whatever you are going to input) and turning it up slowly and watching for known problems such as saturation and excessive spike amplitude. There's almost no way around this phase of the project.I have to ask you a question now too, and that is, did you ever design and build a buck circuit?A buck circuit is a great way to test an inductor that is to be used for a switcher.I hope this helps at least somewhat, and if you really want to get into the deep end of magnetics, take a look at the Biot Savart Law which appears at many web sites. It's at least one of the laws that leads to everything else in magnetics aside from relativistic effects which we usually dont need :-)

author: jbb
author_rank: Super Contributor
timestamp: June 25, 2017, 08:36:18 pm
content: Quote from: MrAl on June 25, 2017, 08:03:24 pmDepending on the mode of the converter, there could be little DC current (discontinuous conduction mode) or a lot of DC current (continuous conduction mode). It can be a bit hard to tel, because your converter may go between the two as instantaneous line voltage changes.The mechanism for saturation is that too much magnetic field strength H (Amps per metre) is applied to the (gapped) core set.\Sigma NI = \Sigma H lWhere:N = # of turnsI = current (A)H = magnetic field strength (A/m)l = path length (m)Note: the \Sigma symbols are there to handle multiple windings (e.g. transformers and coupled inductors), and can be ignored for a simple inductor.Then magnetic flux density B can be worked out:B = \mu H\mu = \mu_r * \mu_0Where:B = magnetic flux density (T)\mu_r = relative permeability (see core material datasheet or 1 for air/plastic)\mu_0 = permeability of free space (4 *pi * 10^-7 H/m)I forget how to handle the air gap, though. I think you set the B values in the core and air to be equal, but I'm not certain. I could look that up tonight...Anyhow, we see that the easiest way to look at saturation of aninductoris simply to check thepeakcurrent. (Transformers are quite different!). As it happens, a lot of current mode control schemes are designed to immediately switch off the power transistor if the current reaches a peak value. This combination is great, because it means that with a little care on the controls side you can be very confident about not saturating your inductor :-).

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: June 26, 2017, 11:31:45 am
content: Quote from: MrAl on June 25, 2017, 08:03:24 pmI spent all day homogenizing the equations from all of the books to use u0properly.Biot Savart Law is EXACTLY what I've been looking for. I just didn't know how to find it.QuoteThe good book I found(in SI units), actually has a number of equations precisely for boost inductors, covering; IL, VL, D (which I knew already but forgot due to the long break), ripple current, IL(RMS), VL(RMS), L, Apparent Frequency and I already know how to calculate N from L then augment the value by the square root of um/ue, based on: um/1+um(lg/lm)QuoteI've actually seen that, that article it was very helpful. Is fringe flux factor a big deal at all? Because you and another person that I asked about it don't seem to give it much importance, but the books make it seem pretty nasty.QuoteI haven't built the inductors yet, I want to get the equations all correct first. I don't want to short out my new monitor, lol.QuoteMy guess was the MOSFET voltage should be more or less double the VDS(in)The reason for the MOSFET/Output voltage question is because I know it's probably better to boost to about 400V, but I know there's less current stress on the transformer if the input voltage is higher.Let me explain the project to you in detail:I'm building a DC-AC-DC converter with 2 PFC inductors ,using 2 mosfets(FCH060N80), boosting to 400VDC (or 800V with 1200V 45A SiC MOSFETS to reduce current stress on the transformer), operating in opposite phase of each other. The total output power of the PFC stage will be 1kW(500W output from each inductor), powering 4 FCH023N65S3_F155 MOSFETs, providing an alternating square wave with a deadtime to avoid shorting. I've chosen this topology to maximize on core useage. The secondary winding will provide a rectified output voltage of 100VDC(I'll probably add a tertiary 12V for cooling fans), buck-boost output regulator to enable a variable output voltage. Size or part count isn't of primary concern, efficiency of operation is (I have 100s of kickass MOSFETS, among other components). I may program an MCU to control the FETS to monitor voltage and current, but I believe this can be achieved with linear TTL logic(more fun that way).I know I can get a lot more output power from the converter I've described, however I only have 20A available in total (unless I go in the kitchen where there's 30A) and I don't have a sufficient load to test the device above 1.4kW however I will add the appropriate components and windings to increase output power as needed.QuoteNo, but what actually got me into electrical engineering were boost converters. I bought a few cheap $5 converters, tied them to the 12V rail of an ATX PSU and after a few days of being hooked they kept blowing the MOSFET when I applied a 30v 100w load (COB LED) to them, so I took one apart, re-wrapped the toroid with some homemade litz wire and center tapped it to take the stress off of the MOSFET(which worked very well,lol), what I called a flyback autotransformer at the time, and made a freaky boost converter that worked amazingly well, being I totally did it spatially, no inductor calculation at all. All I calculated was the winding ratio between the primary(lower) and secondary(upper=2*lower)Look at this crazy ass thing:I had that thing running as lamp in here for months(MOSFET heatsink stayed slightly warm the whole time) until it fell off of the table and the heatsink fan on the LED shattered (never bothered to reassemble it).I've learned so much since then. The crazy thing is that it actually did what I expected. At a 50% on time it was 36V(40V no load) because the upper portion of the inductor had twice as many windings as the part that I was exciting. I was able to get that thing up to 45V before its little 10A breaker button would pop. It killed a couple of red COBs but the white one could handle excessive voltage with no problem. After that thing I was hooked on power electronics.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 26, 2017, 01:33:57 pm
content: Quote from: hanzdolo30@gmail.com on June 26, 2017, 11:31:45 amI would suggest not worrying too much about the nitty-gritty. Biot-Savart is great for physics problems, but you shouldn't need it in electronics problems.The biggest drawbacks are:1. There's no good way to integrate over the surface of a winding.2. There is better symmetry to shortcut these problems with.#1 is particularly complicated by the fact that the current doesn't flow uniformly through the wire, and the wire is not transparent to magnetic fields. It would be easy enough to integrate along, say, a helical path, but wires are not infinitesimally thin; if you add a cross-section to it, now you're assuming the current is distributed somehow over that cross-section (which it isn't).It's another way of saying: that one particular equation is magnetostatic. But conductors at AC have resistance, so the EMF (from self-induction, causing skin effect; and the total induction, that gives us circuit inductance) is nonzero.It's important to understand how this stuff works, but it's devilishly hard to work a real problem with.As for symmetry, Maxwell's got you covered: for an infinitesimal cube, with field lines parallel and perpendicular to the sides, all the equations are simple proportions. Flux is flux density times area; EMF is loop area times flux change; field intensity is current over path length; and flux density is field intensity times permeability. (Clearly, if EMF and current have a relationship -- as in a resistive material -- you need to add extra terms to represent that.)Nice thing about magnetic cores: since the flux is almost all (99%+) confined to a core, we don't much care that the core is itself going around some kind of path, we just care that it has length and area -- we can consider it as one rectangular chunk, where the field lines are parallel and perpendicular to the sides!Just as we don't need to integrate over SMPS waveforms if they are straight-sided, we don't need to integrate over the core if it behaves straight-sided.So these "square wave" or "square block" symmetries help out a lot!So for analyzing a core, it's enough to use Maxwell's laws directly, where each law is simply a ratio. We don't need to do vector calculus, because we've applied geometry that gets rid of all the nasty dimensionality and leaves us with scalar proportions (width and height, magnitude and sign). We don't need any constants, no random pi's and such, only bare fundamental constants; namely, B = mu * H.QuoteFringing flux is a problem for two reasons:1. The intense field strength, and its nonuniformity (that is, it doesn't behave as a simple parallel rectangular region), induces eddy currents in nearby wires, causing heating (proximity effect).2. The fringe location acts like a winding of the same size, which transmits fields out into space. Thus, it's a source of emissions. You often see transformers with a copper tape wrapped around the outside (notice it goes around the whole core, not just the winding where it would be a shorted turn!), which acts to short out (shield) this mode. In other words, it keeps the flux inside the core, where it belongs.Related:http://power.thayer.dartmouth.edu/shapeopt_intro.htmlThis calculates where to optimally place wire, to avoid those losses. Cool!Tim

author: MrAl
author_rank: Super Contributor
timestamp: June 26, 2017, 02:09:10 pm
content: Quote from: T3sl4co1l on June 26, 2017, 01:33:57 pmHello there,I think that post was well written for sure, and i dont want to take much away from that by disagreeing with one point only, but i must disagree a little when it comes to the Biot Savart Law, and theories that lie in that same natural world base class.We have basic theories and first principles for a reason. That reason is not to mock the absurdly abstract, but to use them as a basis of further understanding. Even if we cant calculate the six dimensional integral required for a certain inductance calculation, we at least know where the inductance originates. We can also sometimes turn to other simplifications that allows us to go back to the original statements and use them after substituting the simplifications into the original problem. For example, the geometric mean distance and it's use in magnetic inductance calculations, and other simplifications like that. So there's never going to be a loss because we studied Biot Savart a little because everything that comes after that builds on that basic theme. It's good to be able to see the forest, but sometimes it helps to see the leaves too (a reference to environmental analysis based on leaf count).Also, some things that were not subject to direct calculation yesterday are able to be calculated today. Elliptic integrals being one example, where many years ago the goal was to come up with formulas that did not have to use them, while today they are much more easily evaluated using symbolic math programs (Wolfram for one example).If you disagree, you might ask yourself if we dont need it then why did you learn it :-)Because you had learned it you know about the difficulties and how it may be used, but if you did not learn it you would be asking right here about what significance it has in magnetics.We have a lot of theories on hand, we dont always use every one of them every day, but when we want to know something about the nature of a problem we have to turn back to them to know for sure why something is happening the way it is.Granted many people will not be interested in the basic theories of nature, but when questions like the ones i've heard in this thread so far come up, i feel that the askee has the kind of mind that wants to know the whole story, not just part of it. We sometimes dont want formulas thrown at us. Yes, Biot Savart is a sort of formula too, but it's a more basic one that digs right to the root of nature. If you want to find a derivation for that though, you could do that too, and after all, you are willing to accept Maxwell as a basic concept of nature even though that one has a few open ends yet due to Einstein.In the end, we all have our level of perfection that we want to strive for. Everything is an approximation to some extent, but sometimes we want to get as close to nature as possible. The Biot Savart Law is a beautiful way of looking at the nature of magnetics, it would be a shame to miss out on it for someone who really wants to understand.

author: MrAl
author_rank: Super Contributor
timestamp: June 26, 2017, 02:13:07 pm
content: Quote from: jbb on June 25, 2017, 08:36:18 pmHi,What i was saying basically was that if you are designing the converter and you dont know if it will saturate, then you dont know if your design will work in the real world, and that sounds a little flakie to me.

author: MrAl
author_rank: Super Contributor
timestamp: June 26, 2017, 02:29:47 pm
content: Quote from: hanzdolo30@gmail.com on June 26, 2017, 11:31:45 amHello again,Yes i forgot to say sorry to hear about your monitor problem. Maybe you should find a way to isolate that from whatever else you are doing. I hope it was not too expensive.The fringe flux is a contributor to lower efficiency. That's the main concern in modern converters i think because the goal today is to get as high as possible. You do have to realize though that what you are doing is partly academic in nature, as often we dont have the luxury to pick and choose everything we can use. Sometimes we have to start with whatever is already on hand or accepted as standard and go with that.For example, a company may have purchased a large number of EI laminations of a certain size, so rather than order a bunch more of a certain more optimum size we have to make use of what we already have. It sounds like you are doing this too i think to some extent.If we had our choice and if we could find a suitable core of course, we would go with a lower mu core. A larger gap produces more fringe, so going with a smaller gap would be more efficient, but then we might not be able to get the right inductance and DC current handling we need, because really we need a bigger gap with a certain fixed mu core. But what about using 2 gaps. We can use two smaller gaps in the same core and thus get smaller gaps and less fringing, but why stop there. What if we go to N smaller 'g' gaps, where g=Gap/N. That's what a distributed gap core looks like, and so that would help efficiency.But if we are stuck with a core we have on hand, then we are very limited to what we can do. If the inductance is too high and/or DC current causes saturation, then all we can do is add a gap and add more turns. If we can create more gaps, then we can go with the g=G/N idea, but that's not usually easy to do either. So we usually end up with one or two gaps and that's about the end of it.So your optimum gap is the smallest gap you can get away with and still get the other requirements you need.The gap isnt really ignored, it's just hard to deal with when you dont have the free choice of core metal to use.Before ASIC's and uC's came about, TTL was one way to make commercial converter control circuits. The gov purchased many of these things, maybe because the reliability is so decent.As a final note, gaps should be ground to high precision. What we dont want is a partial core saturation which effectively lowers the core permeability which in turn could cause a higher current in the winding.

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: June 26, 2017, 11:01:23 pm
content: Hi, It's good to hear from you again,Quote from: MrAl on June 26, 2017, 02:29:47 pmThe monitor was a rather inexpensive SEIKI, but there was no dynamic image processing, so it served my purpose well (nice clear text). It was an irritating loss, because I'm a developer/IT professional by trade (I've been coding proficiently since I was 11, in 1988 when you could write ASM code into RAM with DEBUG and save the memory segments to disk as a .COM file) and I'd purchased it to have a higher resolution, in order to enable me work on multiple modules simultaneously. The replacement I'm using now is a Toshiba with some sort of dynamic image processor with poorly written firmware, better suited to be used exclusively as a television(slightly blurred and discolored text). However, when life serves lemons, one must make lemonade!At the time I was unaware that a short in my little startup circuit, (which was completely my fault because I allowed the legs of a voltage divider to cross each other, because I didn't cut the leads) could cause a feedback current that would affect other devices on the AC end of the rectifier (which was completely undamaged after the incident).Now I use a separate power strip with surge suppressor on a mains line that doesn't have anything important attached to it.QuoteWhen I initially looked at gapped cores it seemed a bit counterintuitive, being the fringe flux is actually feeding MMF back into the coil creating what would appear to be an unwanted "mutual inductance" at the gap area. Which is why I initially asked you if it was a good idea to create a bridge between the gap and the at the residing region of the gap, on the bobbin, proportional to the distance of the flux radius, to avoid the undesirable effect.I may take the i(t) (current as a function of time) approach, where tao=L/R, where 5tao is the full charge time, and use Euler's Method to time the charge of an inductor (easily calculated and implemented using RC timing and a number of other factors, I'm sure you're aware of so I won't bore you with the details). If the ueis calculated correctly the slope of the B-H curve can be made perfect. It's all about the gap and how the nasty fringe flux is handled, from what I can gather.I'm quite aware of the academics involved. Freelance IT work is dead as fried chicken (which is where the $ used to be),lol, and I'm not enjoying development as much as I used to, due to the constant change in "climate", due to the constant emergence of new API's (we used to call them libraries) and the need to use them because; "It's the new cool thing everyone wants!", which is why I'm turning in the direction of engineering. My long term is to pursue a PhD in applied physics (planning to start this fall).QuoteOh I know, I'm 41, I grew up in the 80's and 90's and RadioShack was my favorite place to be (I eventually ended up working there, being I knew the manager so well). TTL circuits are actually quite reliable, as they are not susceptible to ESD damage, due to the lack of CMOS transistors on the die of the IC's. Which is why I'm leaning in that direction when it comes to power converter control circuitry. I know I can write a kickass advanced control scheme into one of those ARM Cortex M7 chips, but what if there's a nasty power surge? DEAD PSU that's what. Which is probably why they're usually placed on daughter boards, for easy replacement (I've seen this in some of the better PSU's that I've dissected).QuoteHave a couple of shattered E cores that I've practiced grinding down with a diamond file set. I've noticed that the best approach is to measure it with the caliper, marking the core with a white pencil, just below the point where I would want to stop, filing it in a circular motion using decrementing grits, to get it within +/- .01mm of accuracy. It takes a while but, I carve wood and wax sculptures, so I have the patience for it.I would Like to add, This has got to be the BEST forum I've used on electrical engineering. Because of the members. Everyone here has been friendly and knowledgeable, though I've noticed everyone seems to have their own style of doing things, which is cool, being a non polarized thinker, I can merge the knowledge. The only complaint I have (because I am a developer and I could rewrite this HTML editor within a week and that's an overestimation), is the inability to use some sort of script to lay out the mathematics properly(like MathJax). I mean thisisan engineering forum and we use complex equations all the time.When I lay out a formula it's like talking to Excel(which were not in the 80's anymore and we've been in the age of GUI for over 2 decades, so Microsoft should have improved on it by now). I just had an epiphany, I'm going to start writing my own spreadsheet program properly suited for scientific mathematics. If one exists I would love to know. I can't seem to find one.

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: June 27, 2017, 12:37:08 am
content: Hi Tim, Great to hear from you again,Quote from: T3sl4co1l on June 26, 2017, 01:33:57 pmFor the sake of this and other DC-DC/DC-AC conversion projects, in order to expedite the process, I totally agree that Maxwell's Equations are sufficient, but I do want to learn all about the Biot Savart Law for the sake of knowledge. Which is why I was so happy to find out about them, as it provides a lot of the details.QuoteI knew that nasty fringe flux was an issue, because just looking at it in an illustration of how it exits and re-enters the core, it's obvious that it will cause a secondary(mutual) feedback inductance in the primary coil(its source), which would obviously cause inductance issues, as it is pumping current back into itself. I know the gap is essentially an MMF resistor, so like a resistor the gap must dissipate the energy in some form(like resistors do heat). I was trying to reason how to shield against it, I thought about maybe wrapping some copper foil around the region of the gap on the bobbin, prior to applying the litz wire, to catch it, but quickly realized that it would act as a shorted secondary winding like you mentioned above, so I never bothered asking if that one would work. So my second Idea was to simply calculate the distance(blast radius) of the MMF radiation produced by the gap and put a few layers of teflon over it of the same thickness. Would that work? I know it must change Aeat the gapped region so it would change inductance values proportionally but wouldn't there be a way to calculate that proportionality?I've only had a chance to briefly go over that link you sent. I just printed theOptimal Core Dimensional Ratios for Minimizing Winding Loss in High-Frequency Gapped-Inductor Windings, PDF.I'm gonna go read it right after I'm done with this post.Thank you, you always drop some really good Gems on me!BTW, did you see the schematic of my first boost converter?It's the BJT Astable one I was telling you about.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 27, 2017, 10:35:26 am
content: Quote from: hanzdolo30@gmail.com on June 27, 2017, 12:37:08 amIt could be shielded by wrapping the core with solid copper foil, that is insulated so it doesn't form a shorted turn where it overlaps. This way, the field fringes outward at the gap, smacks into the foil, induces current*, and pushes the field lines back towards the gap. What you would see in a plot is, a couple field lines push out and penetrate into the foil (a few skin depths; if the foil is thinner than the skin depths, a noticeable amount will leak through, still going on to touch the wires; if thicker, it will bend back and follow along through the foil, until coming out at the other core face). The rest of the field lines are confined within the core gap area, but are particularly dense around the corners (because there's a "pressure" for those lines to spread out -- hence fringing in the first place -- and the copper strip packs them back in around the edges).*Way more total current than would be induced in loose wires, but the same resistivity (copper is copper), so you can guess what this will do to the losses...So as is often the case -- better to let it happen, than to try to fight it. Moving the wire away from the gap by adding a large spacer around the middle of the bobbin, or using Litz (that simply has a smaller eddy current cross section), is the way to go.The fringe is about as wide (distance from side face of core to nearest wire) as twice the gap, and about as tall. That is, keep wire away from about one gap-length above and below the gap, and two gap-lengths beside. Or maybe three. It's inverse-cube in any case, so it drops off quickly.Tim

author: MrAl
author_rank: Super Contributor
timestamp: June 27, 2017, 02:53:19 pm
content: Quote from: hanzdolo30@gmail.com on June 26, 2017, 11:01:23 pmHi,The way i handle math format differences is i write programs to convert between styles. That's the only way i have found so far to use whatever program i want to use when i want to use it, or else i just cant use some programs.Since i grew up on text however, i have no problem reading text equations, and i usually prefer that format because then i can copy and paste it into a program and i am up and calculating within minutes.For example, i use one interpreted language for my home made formulas (as well as others really) that does not know how to handle the exponent symbol commonly used for exponents like in 2^9 which represents 2 to the ninth power. Since i got tired of changing all of those occurrences in a formula by hand, i started writing small easy to modify programs, one of which converts a^3 for example into a*a*a and if there is more than one occurrence it makes a constant a3=a*a*a and then inserts a3 into any place that formerly had a^3 in it.There are so many variations though that i ended up creating several small programs, another one that removes "abs" from the equations, because sometimes we dont need that when dealing with all positive numbers, yet a solution may come out with several of those in it.The simplest way i have found so far to facilitate this kind of conversion is to have the program interface with the clipboard. Then it is just a copy, run, paste, and the new equations are pasted into the required app.You may have some other good ideas here too since you do a lot of programming.

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: June 28, 2017, 08:48:40 am
content: Quote from: T3sl4co1l on June 27, 2017, 10:35:26 amHi Tim, I hope your day went well,I'm actually amazed that I was remotely correct about how to shield the fringe flux radiation. Though I am aware of the existence of a Faraday's cage, and came the foil assumption based on that. However, I did think distancing the air gap from the litz wire would actually work.There's one thing I'm not clear on. Being there will be a slight increase in the coil area where the spacer exists, wouldn't that increase the AEat the spacer, affecting the inductance value?I just want to be sure I'm understanding this correctly. Are you telling me that If I use Litz I don't have to use a spacer?I was always planning on using Litz Wire for this project. Being I'll be operating the inductor at 100kHz, I figured it was a prerequisite, due to skin effect.Thanks.Gilbert

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: June 28, 2017, 10:58:29 am
content: QuoteHi,I've realized that writing a full blown spreadsheet would probably be overkill for now. So I'm going to take your approach and write a quick desktop application in C# to calculate equations for magnetics, to do things like, plot B-H (Hysteresis) curves, i(t), v(t), U(t), . It'll be a lot easier than dealing with cell numbers and long one line equations in excel. Honestly It'd be easier(on the eyes) to write a script in js and use canvas in an HTML file to plot graphs than to deal with Excel, lol.Thanks

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 28, 2017, 11:26:23 am
content: Quote from: hanzdolo30@gmail.com on June 28, 2017, 08:48:40 amYeahI'm not clear if you meant to wrap the gap, all the way around, with a solid (shorted) turn of foil -- if so, that's a big difference,but just that subtle change (leaving it overlapping but insulated) makes it workable. (I mean, besides the problem that air gap fringing is just too vicious to shield.)Placed between windings, this is also how an electrostatic shield is made.Shields also enforce field uniformity, so they're useful in precision (balanced / bridge) transformers and RF.QuoteCoil area doesn't matter: very little flux flows in the air beneath the coil. That's the point of the core.That said...The fact that the fringing extends out from the core, means, yes, the effective area is increased at that point!So you're again not entirely wrong!The effect is that, as you increase gap, the Ae of the gap increases as well (basically by adding gap length to all sides; if you assume it remains a square, that makes the new area,Ae' = Ae + 4 * (l_g * H + l_g^2)Where H is the height of the core. (Or similarly for a round core, changing H for D (diameter), and 4 for pi, so that the diameter is increased the same way.)That means you need slightly more gap than calculated (from a linear method), because the gap has lower reluctance (more area) than you were expecting. And that also means this is only important when the gap is relatively large compared to H, say 5% or more.Even further into the weeds, we can contemplate the core geometry itself; the fringing flux affects the core as well, so that flux is concentrated on the edges of the core faces (recall how metal filings hang off theedgesof a bar magnet!), which makes the corners saturate earlier. The core face could perhaps be rounded off, which would make the fringing volume even bigger (a downside), but would have the effect of sharpening saturation (i.e., the whole core saturates at once, more nearly).But that's more of a digression, than anything you'd do; it's much cheaper to simply get the next larger core size, than to try and wring every last mT out of a core.QuoteYes, though it depends on the Litz of course. Regular Litz, for carrying currents in cables, let's say, won't work as well once it's inside a transformer: because of proximity effect. Proximity effect is exaggerated when you have multiple layers carrying current in the same direction, so it's hardest on multilayer inductors. Transformers (including coupled inductors like flyback transformers) can be wound with alternating primary and secondary layers, to minimize proximity effect. (This is one advantage of forward converters: the primary and secondary currents oppose, so that a construction with alternating layers doesn't incur any extra proximity losses. Flyback converters don't carry primary and secondary currents simultaneously, so the losses aren't reduced by current cancellation: but the reduction of leakage inductance is more critical for this, so the alternate construction is still important.)Further, because the fringe field is intense, it might be that you need Litz made with several gauges finer strands, to avoid excessive loss near the fringe.For sure, don't make a marginal design where the Litz isjust barely good enoughin the rest of the winding -- then the part deeper inside (subject to proximity effect or fringe eddy currents) will overheat.But in general: absolutely, without a doubt, Litz is better, whether it's placed near the gap or not. There may still be some advantage to avoiding the fringe area, but likely you'll be fine to put it there: don't worry.You definitely have to worry if your strands are rather coarse. Why coarse strands? You'll find sometimes it's easier/cheaper to build a transformer with several individual strands, laid down in parallel, or twisted together. Maybe you don't have Litz that size, or don't want to splurge for it. An inductor designed for low current ripple will even be fine to make out of solid wire. But if these materials are wound on a cut and gapped core, they may burn up near the gap, due to induced eddy currents (instead of load current). This would be a situation where you'd add a spacer in the middle.There are also good reasons to add a different kind of spacer, like this,Which has more to do with reducing the capacitance between sections. The insulation voltage also goes up. These are commonly seen in high voltage transformers (including CCFL drivers).And, apparently, whatever this transformer was doing. It was removed from a CRT monitor, so a couple of those windings are mains voltage input (~350V, probably switched at ~140kHz -- flyback), a couple would've been ~100V output (for deflection and CRT driver), and a couple for logic supply (3.3 to 12V, say).The single split bobbin design is also very common in mains transformers, where the huge isolation voltage is a plus, and the high leakage inductance is not-a-bug-it's-a-feature (crappier regulation, but reduced harmonics, fault current, and in the smaller sizes (< 20VA or so), tolerance of continuous short circuits).Tim

author: MrAl
author_rank: Super Contributor
timestamp: June 28, 2017, 12:53:34 pm
content: Quote from: hanzdolo30@gmail.com on June 28, 2017, 10:58:29 amHi again,Sounds good, i use C and C++ and an interpreted language but havent used C# yet. I do mostly console applications for these tasks because they are so quick to write up, but i've gone to Windows applications for more versatile programs with interactive user interface and nice graphing. The console programs go so quickly though that i usually run to that just to get something calculated where there will be a lot of repetitive calculations (funny integrals and the like).What magnetic model are you using to do the BH curves?

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: June 28, 2017, 08:19:47 pm
content: Quote from: MrAl on June 28, 2017, 12:53:34 pmHi,C# is nice if you're writing something where you'll need to spin up a quick UI, but for services, video processing or anything where managed code would slow you down, I prefer to go native with C++. Though in the case of services, if the task is light weight, you may want to consider using C#.For console applications, as of last year, I tend to use nodeJS. It's fast and if you're familiar with javascript, you'll know that objects are quite versatile.Using node, I was able to put together a full featured MVC framework, similar to MVC.net, within about 45 days, using absolutely no foreign packages (I wrote all of the modules myself).That was my introduction to node. I usually take on difficult professional level projects when learning something new (like power converters in EE, for example), rather than wasting time with little "Hello, world!" programs (In EE, I'm guessing blinky LED Circuits would be the equivalent).I figure, why waste time, when I must learn everything necessary on the way (jump in and swim method). Otherwise, I get bored and lose interest.QuoteI figured make it as broad as possible by creating a "MagneticCore" class with all of the usual core parameters, um, Ae, le, lg, etc., allowing me to just plug in values as needed.

author: MrAl
author_rank: Super Contributor
timestamp: June 29, 2017, 01:48:38 pm
content: Quote from: hanzdolo30@gmail.com on June 28, 2017, 08:19:47 pmHi,Actually i was asking for the model you use for plotting the BH curve really. Not sure if that is what you are doing now or not though. That would be a formula or set of equations.

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: June 30, 2017, 01:40:42 am
content: Quote from: T3sl4co1l on June 28, 2017, 11:26:23 amI figured a shorted foil was not the way to go, because would be the same as starting up a flyback (coupled inductor) with a full short,. My idea was actually to run leads from the foil winding to capacitors, being caps are an AC ground, but I wasn't certain if that would've been a good solution.QuoteSounds like more trouble than it's worth.Onward to Litz...QuoteHey Tim,I thought the gap spacer would be the perfect solution, but it seems that using litz is the way to go .I'm still a little confused about the litz though, but I'm sure you'll get me straight after this question.It seems you're telling me to use multiple gauges in the same wire or is it a matter of the number of conductors.?With the low voltage converters, I usually use recycled toroids from old PSUs,I spin the litz on a couple of 9/0 fish hooks, one end stationary and the other slowly on my drill, adding as many conductors as necessary to handle the greatest potential current going through the inductor. Can I use the same method?I'm planning on using 26 AWG being the max skin depth is 107kHz and my target frequency is 100kHz, but I do have about 30' of some premade 50/32 AWG litz I bought last year, should I use that instead?

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: June 30, 2017, 02:54:07 am
content: Quote from: MrAl on June 29, 2017, 01:48:38 pmHello again,Oh, I see, you were referring to the set of equations I was planning to use. I haven't started putting those together yet, but I was planning on using the equations provided to me by the textbooks.Is that how I should be doing it?I read that the hysteresis curve changes based on ue(ideally, wanting a perfect slope from -B => B), where; ue= um/1+um(lg/lm) and the level of excitation of the inductor. I was planning on writing a program that'll provide me with the ideal, ue, based on my desired power throughput, which(if I'm not mistaken)will be able to compute the necessary lg, along with other necessary factors, then graphically plot the hysteresis curve. I.e., a program that'll compute the exact design parameters of an inductor that cannot be saturated based on the necessary power output, input & output voltages, core geometry and material properties.Does that sound about right?Please correct me where I'm wrong.Thank you very much.

author: MrAl
author_rank: Super Contributor
timestamp: June 30, 2017, 11:32:56 am
content: Quote from: hanzdolo30@gmail.com on June 30, 2017, 02:54:07 amHi,Oh ok, i just thought you had some on hand that you could show here so i could take a look. There are different equations used in magnetics so i always welcome the chance to look at what might be new ones or something.If you got them from a text book then i guess they include all the necessary features. If you get around to showing one we could take a look.

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: June 30, 2017, 02:28:43 pm
content: Quote from: MrAl on June 30, 2017, 11:32:56 amI didn't realize how rusty I was, it took me 4 hours to get back into the swing of things. I haven;t touched C# in about 4 Years. I was oblivious to the fact that C# uses Math.Exp(value) to handle exponents and apparently javascript does the same so I wasted a few hours (trying to be a perfectionist) trying either create a new operator or add the ability to the variable type like 3.toString(). No luck there so I guess, I'll have to go the long way;Visual Basic has the ^ operator but I haven't touched VB in so many years, it was just weird being in there. I'm not sure if you're aware of this, but MS said they were going to drop VB back in 2011so it was much to my surprise when 2017 had VB in it's list of languages. Basic was my first language,but after working with braced languages, It's difficult to turn back. I may go Javascript. I can build all of the math into an object. The beauty of JS is that you can write functions into the objects. I'm trying to decide. I guess I'll have all three compute a core of the same value and see which one I can build the best UI for.This is a controller from My Framework Just to give you an example:API EngineControllersNow that I’ve gotten to the part where I’ll have to write the controllers, I’ve found that the best approach to forming API methods is to form them the same as you would if you declared any other java script class with the exception that there should be guidelines followed in order to use the helper methods written in to the controller module.Basic construction of a standard controller class should be as follows//This is an example of a root folder controllerfunction defaultController() {// this is routing and security informatiomthis.aliases = ['/'];this.authorize = true;this.methods = {index: {aliases: ['/', 'default', 'index'],GET: function () {returnView('default');}},about: {aliases: ['/', 'about', 'aboutus', 'about_us', 'about-us'],action: function () {returnView('about');}},contact: { // aliases which call the get methodaliases: ['contact', 'contactus', 'contact_us', 'contact-us'],// GET request sends the defaultGET: function () {returnView('contact');},PUT: function () {// Do things to send email from fields upon contact form submission}}}}//Controllers should pass url parameters by dividing them into Controller = Param, action = param, other named parameters will be defined by the user while being defined in an object local to the controller by name.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 30, 2017, 04:22:32 pm
content: Quote from: hanzdolo30@gmail.com on June 30, 2017, 01:40:42 amElectrostatic grounding has no effect on the magnetic field, of course.QuoteHmm, I suppose you could use multiple sizes in the same wire, but that would be annoying. And hard to arrange optimally, because you'd want the finer strands in the middle. But you want the strands always circulating in and out, hence the woven construction of Litz, so that's impossible!Just a matter of the number of strands, what size strand you start with in the construction of an equivalent size cable.QuoteHmm, ferrite or powdered iron? You usually see the latter (yellow-white or blue-green colored), which is very lossy material (by 100kHz, it's practically a better resistor than inductor!).QuoteThis is a poor way to do it, because it strains the wires, and doesn't make a tight cable anyway (it springs back a little).Unfortunately, the proper way to do it isn't very easy (you need one spool for each strand, and the spools need to rotate freely, so as the wire is drawn off and twisted into a bundle, the spools rotate at the same rate).If you only need a few meters, it's not terrifically annoying to weave or twist loose strands together in the same way (no spool needed if they're loose... just don't let them tangle up..). Otherwise... it's one of those cases were "poor" is about all that's feasible to do.QuoteThat sounds good. Maybe save it for something fancier, though?Note that, because of proximity effect between turns, and within the cable itself, the skin depth is considerably shallower: 26 AWG is one skin depth (approximately) for a single solid wire at 107kHz, but buried under layers, the skin depth may be more like 30 AWG equivalent. Using a Litz cable built with that strand size would help, but still wouldn't be optimal; you might need to use 38 or 42 AWG strands to get AC resistance down to nearly the DC resistance.So, of course, it's a tradeoff; if you don't need ACR being as low as DCR, who cares. If you need maximum efficiency, you need surprisingly fine Litz.For small converters, and where you aren't terribly worried about efficiency, losses can be quite high, and solid wire is fine.You can also double it up, so you're using more wire than you should need (based on DC ampacity), and it won't be optimal at all (because it's made of few, large, strands), but it's still better than just one (even if not strictly N times better, with N strands -- because of proximity effect).Tim

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: June 30, 2017, 08:34:01 pm
content: Hey Tim, Good to hear from you,Quote from: T3sl4co1l on June 30, 2017, 04:22:32 pmYeah I know. I just figured, I'd run it by you anyway. The Idea was that it would ground the current in the shielding keeping it from burning up cooler, but that only works in biased amplifiers. Even if that worked there would be a power loss.QuoteDo you mean like desoldering braid?My cats would have a field day,.QuoteThe black powdered iron boost inductor toroids. The green ones are just for filtration, right?The yellow ones get crazy hot at 12V 75kHzQuoteYeah I know about the wheel, but I do a pretty good job with my drill (i've had my share of birds nests,), I just wrap the strands around the hooks with tension, then I put one of em in my drill maintaining tension, spinning as slow as possible following the cable as it gets shorter, being sure not to let it stretch, being the twisting flattens it a bit increasing the skin depth. It's usually perfect when I'm done. I'll upload a pic when I'm done for you to see.But this conversation is making me wanna use that 50/32. Is kinda thick(1.7mm).I was planning on using it in the transformers.QuoteI'd rather add more strands and have less resistance.I do have a spool of 30 awg, would that be much better?I've spun 30 before and it has less memory, but you need 3 times the strands to carry the current.QuoteTim, I'm sanding inductors for a dual phase PFC stage, don't you notice I'm being kinda OCD about this, efficiency is the goal!Seriously though I do have like 50 EE25/13/7s should I make smaller ones to play with first?Though I didn't think they'd be good enough for 400V boost inductors. I was planning on using of them to make flybacks, for powering the primary.I've never used an optocoupler...Nevermind, we can talk about that later if you want (I Must be driving you crazy) .

author: MrAl
author_rank: Super Contributor
timestamp: June 30, 2017, 10:41:41 pm
content: Quote from: hanzdolo30@gmail.com on June 30, 2017, 02:28:43 pmHi,Dont feel bad i havent used Java yet at all. I meant to get to it, but never found any good tutorials on it on the web.A magnetic model would be a formula or set of equations like this, which could be written in any language:B=f(H)*uwhere for example f(H) for a very very simple example (and this whole thing is over simplified anyway) for a linear core:f(H)=H*uor in terms of current we have a function B such that:B(i)=i*Kwhere 'i' is the current and K is a constant. Obviously there's no hysteresis in this over simplified model.Some of the sites i found for Java seem to be broken too. Know any good sites for starting in Java?

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: July 01, 2017, 01:06:29 am
content: Quote from: MrAl on June 30, 2017, 10:41:41 pmYou know, I haven't gotten around to java either, but whenever take a glance at java I always assume it's c# until I really look at it.I'll Find you a good PDF, it's a PROMISE!I got back into the swing of things, it's like riding a bike,lol. However I did choose VB because it's much easier to deal with exponents, which as you know, we deal with all the time and it has the same user interface as c#. nodeJs is awesome, if you're writing network based applications.That code I showed you earlier is one of the help pages from the framework I wrote. There are 3. The controllers are actually that simple to write. No routes configuration necessary, upon server startup it:1.Reads the main configuration file2.Locates all of your controllers based on the directories specified, notifies you of any routeconflicts and autocreates your routeconfig.3.Serves your index file as specified in the routeConfigThat's all. There's Serverside Javascript support in the Views, but the models can be messy, so I leave that to the discretion of the developer, everyone has their own style and favorite ORM so, I decided not to stand in the way of that by cluttering the framework.After looking at it today I realized "Ah the broken monitor!", I't not 100% done yet. I'd day 85%Check out the attached PDF, It explains it all in 3 pages with full examples.Give me your honest opinion as a developer. What do you think it could use? I can provide you with a copy of the configuration folder if you'd like so you can get the full gist of how it works.Please bear in mind this is my very first node JS project, ever. I didn't use any external packages.I wrote all of the modules.There's just 1 very important thing that I didn't get to finish and that's POSTs.

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: July 01, 2017, 03:44:34 am
content: QuoteHere you go:Introduction to Programming Using JavaTeach Yourself JAVA in 21 DaysJava The Complete ReferenceI paged through them all, IMHO. They have everything an experienced programmer needs to learn Java.It really is a lot like C#. I went through it quickly, but I think that there's an exponent operator.Thanks for all of your help, it's the least I could do.I was just imagining usingMath.Exp(n);every time I had to use an exponent and quickly I decided to continue writing the application in VB. Visual Basic is the only language in the IDE that has an exponent operator.BASIC was my first language so I am familiar with all of the operators in the language. There won't be any surprises.I'll probably play a bit in C++ later on also. I haven't written not a line of C++ since 2013, I need the practice. Especially with a lot of MCUs using it as a native language.

author: MrAl
author_rank: Super Contributor
timestamp: July 01, 2017, 03:00:45 pm
content: Quote from: hanzdolo30@gmail.com on July 01, 2017, 03:44:34 amHi,Oh hey thanks a bunch. The fact that they were in pdf format is even nicer since i dont have to depend on a website to read them.I use C and C++ but much more rare these days because a lot of stuff i have to calculate involves somewhat short calculations even though some of the functions have to be called over and over again, and it is almost always fast enough. I ran into some slowness a few times though,and then i just turn to C or C++ and most of the time there i can get away with just C too.For example just recently i was trying to calculate the geometric mean distance for various shapes in order to try to reproduce some of the inductance calculations from masters of an age gone by. Since they use GMD i wanted to create a program that could do any shape, in the simplest possible way. Well, it worked fine for some shapes but for some shapes it requires repeating the basic calculation so many times that it takes hours to run! Granted, for a given shape i only have to do the calculation once, but i hate waiting that long so i might port this one to C.I still have to recommend an interpreted language though because troubleshooting the code is so much faster. The compilers usually have better error detection schemes so we can get something up and running in less than an hour most of the time. OF course a chess program though is better in C but that's a special purpose program.I'll check out those Java files and see what i can come up with. Thanks again.

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: July 01, 2017, 03:41:42 pm
content: Quote from: MrAl on July 01, 2017, 03:00:45 pmGood Morning,No problem at all. You've helped me a lot. I prefer PDFs aswell, being you can print a chapter, sit with it and work it out. I'm sure you can agree that, it's easier to read from paper than a monitor. I've decided to revert to c# and encapsulateMath.Exp(n)toeX(n). I was severely sleep deprived yesterday and was running on Starbucks, lol. I like Windows forms applications simply because you can just add another tab (like Excel) and you'll have a brand new sheet to work from. You drag and drop your UI and it's off to the races.I have been considering just doing it in javascript in an HTML page, being you can use the canvas tag to plot graphs n stuff. Visual Studio has great intellisense for JS and Chrome actually has strange on the fly compilation going on in there so it's pretty fast. However if you want to save output or anything that would be considered server side, you'll have to make an API in node, which really isn't very difficult.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 01, 2017, 04:41:37 pm
content: Quote from: hanzdolo30@gmail.com on July 01, 2017, 03:41:42 pmI'm going to be adding text inputs and outputs to this page, eventually:https://www.seventransistorlabs.com/Calc/Filter1~.htmlHad the thought of making the setup persistent (cookie based), which often works over multiple clients thanks to cloud accounts (on Chrome, FF, etc.). That avoids having to pass anything through the server.Tim

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: July 01, 2017, 11:41:47 pm
content: Quote from: T3sl4co1l on July 01, 2017, 04:41:37 pmHey Tim,That's a good Idea. You can implement o-auth for that. Makes the user recognition process seamless.I read thef1.js. I didn't see any jquery (I love seeing no canned products). I like the way it works too, very fluid in motion. I haven't really had a chance to work with <canvas/> yet, so it gave me some ideas for my little program (HTML output window to plot things). As you know, I'm writing an inductor design calculator in c#. Right now it's only returning numeric values, but I'll eventually have it plotting hysteresis loops and whatever I realize I need to tack on to it in the future. However, the ultimate goal is to be able to plug the voltage, current, frequency, output power and core properties in and get the application to tell me the rest.I was browsing your site and noticed, you know ASM, lol. I was re-learning it last year so I can start playing with MCU's again, just before I got obsessed with power conversion. That's why I told you something about an MCU in an advanced control scheme. I used to play with Atmel MCUs when I was in my early 20s. I was actually hand drawing (with a sharpie) and etching surface mount circuits. Those types of circuits are so easy to deal with. Batteries a little serial EEPROM and nothing but logic. That's back when you could upload the firmware via parallel port, lol. It's been a really long time since I've done that.I have 3 questions, that I hope you don't mind answering. Being I want to join the rest of the world and stop using through hole components:1. Photosensitive Dry Film with a laser print on transparencies; How small can the SMDs get before the etchant eats through the lines?2.Hydrogen Chloride vs Ferric chloride; Which is better? I used to use ferric, but I also used to get it from the nearly defunct RadioShack. I can't find it locally anymore, but muriatic acid is easy to find, you just add sodium bicarbonate to the waste and once the fizz is done, you're just pouring saltwater down the drain.3.Making your own PCBs; Is it possible to get a roll of foil, some epoxy resin and fiberglass mesh and make your own? Those things are expensive and If I can make em, I figure why not.Thanks,Gilbert

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: July 03, 2017, 08:03:03 am
content: I had to print and read the inductor design chapters of five books this weekend. They each supplied a piece of vital information. I haven't added the Fringe flux factor to the equations yet. I'll add them once I know there aren't any bad equations in there.You know I just found out that the vast majority of the energy get's stored in the air gap. I was also looking for an easy way to calculate N and I found out that L=N^2/R it took me a month to find a book that would explain that reluctance is the reciprocal of permeance (inductance without the flux linkages), because it's obvious that N = Math.Sqrt(R*L);I'm going to turn that into a view file and put it on my website.The entire application is in the calculate button. It's already portable to javascript.Did I get the calculations correct?

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: July 03, 2017, 10:14:40 am
content: Quote from: MrAl on July 01, 2017, 03:00:45 pmI totally get it now. After spending a weekend with my head in books, getting very little sleep for something that doesn't even look so great. I can see the reason for using a interpreted language. You know Chrome in particular has 3D modeling and rendering, you might want to check that out. You can put it up on a site and just have it behind a security wall, like user role based access. That's what I'm gonna end up doing. The days of desktop apps are nearly gone. Unless you have to write some seriously resource heavy, stuff that absolutely has to be in house, you can always make a page and code it in JS. You just use API calls if you want to hide your intellectual property.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 03, 2017, 05:02:51 pm
content: Quote from: hanzdolo30@gmail.com on July 03, 2017, 08:03:03 amIdunno, is this boost? Flyback? Show the circuit. What is DeltaI_L? Is this CCM? What are the units? Show units. Seeing Ae in mm^2 (possibly) and F in Hz (possibly) seems odd to me. The inputs could also be parsed with unit multipliers, whichisn't too hard. Or default units could be selectable (as EEWeb's calculators often do), which is nice for those oddball units like cm^2, and A_L in mH/(100t)^2.Showing waveforms would be cool too. Then, with DCM/CCM resolved automatically and different topologies added, you'd have a fully updated (non-CGI) version of this:http://schmidt-walter-schaltnetzteile.de/smps_e/smps_e.htmlThat is surely icing on the cake, though.JS is nice, very accessible, anyone can use it. Also a snap to add events to all the fields so it updates instantly. "Calculate" buttons are a thing of the past, or they should be. (I've got instant update on my filter calculator, which is doing ~million calculations, and it runs fine -- well, on desktop, at least.)Tim

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: July 03, 2017, 11:01:30 pm
content: Quote from: T3sl4co1l on July 03, 2017, 05:02:51 pmHi Tim,I've been to that website many times and I know what you mean. The calculator UI could have been laid out better and put into one page, but it seems he's an old school, HTML developer or the site is extremely old.The calculator is for that boost inductor I've been asking questions about. F is in Hz and Ae is in mm^2, so you are correct, but I guessed you'd see that. The application took 10 minutes to put together, but reading through all of those handbooks, with convoluted equations, written by odd-balls that do things in cm^2, each using their own strange factors to make them work and inconsistent symbols, is what took all weekend. I had to homogenize a whole bunch of weirdness, because apparently, when you write a book it's fun to confuse your readers by making the equations dissimilar to anything in common practice.I'm not gonna to keep it all in one button, lol. What I meant by"it's already portable", is that it's nothing but values getting pulled from the .text property of the text boxes and plugged into equations and due to the similarities between JS & C# I'd just have to copy and paste. I just want to make sure the math is correct being I'm using my own reconfiguration of the book equations(for the sake of consistency) that I put together on a sleep deprived caffeine fueled weekend. I'm already working on an HTML UI and script on the front end. Meanwhile I'm trying to make sure the math is all correct and reading up on all of the power loss equations to incorporate them. Once I know for certain that I'm not computing chaos,, I'll make it all nice and GUI (I do like your suggestions).It's just that I don't want to lose focus and get lost in the "perfect code", before I have a full understanding of the engineering. For instance, I noticed, as the gap gets larger, the B-H ratio starts to become a slope, where the magnetizing force, H, gets huge and B stays out of saturation and the vast majority of H gets stored in the air gap, but the fringe flux factor also rises. It's like having a digital inductor. Coming to those realizations is exciting and new territory. I did read all of that, but seeing it happen numerically gives me a better understanding of what I've read.Maybe the image I uploaded left too much upto to question, I'll get something basic online and post a link.Thanks,Gil

author: hanzdolo30@gmail.com
author_rank: Contributor
timestamp: July 05, 2017, 06:57:54 am
content: Quote from: T3sl4co1l on July 03, 2017, 05:02:51 pmYeah, you got into my head,. Wrote that last night. You know, I did write a framework, I had just sitting in my hard drive, collecting dust. There'll be all kinds of bells and whistles, for different topologies.I don't want to upload it until I have it down packed.I had another one of those, the more you learn, the less you realize you know, moments., but that's a good thing.Thanks Tim, you've been a load of help, I really appreciate it.Gil