big electrolytics and peak discharge current - Page 1
Forum section: electronics / projects

author: CopperCone
author_rank: Super Contributor
timestamp: June 29, 2018, 01:38:16 am
content: Do dielectrics effect it at all, or can I simply use measured ESR? I mean big like 10000uF 400V in short circuit discharge mode, right up against the terminals. Like if you put a screw driver across it. Does anything funny happen inside at those current levels because of the capacitors nature?I know its probably physically bad for them to do so. I never actually put a screw driver across it. I imagine it might be violent. I would use a remote actuator.They are a bit weird because of the dielectric soakage. I would test it but I don't have a rogawski coil. Don't know how well it would work to make some kind of current divider using bus bars or thick wire so I can measure it using a 10A probe. Mine recharge to like 50V after a full discharge and they keep doing it, so I keep them shorted.I don't know if they deviate from expected behavior or if the local fields inside of them are radically different then with smaller capacitors due to their increased density.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: June 29, 2018, 03:02:29 am
content: ESR isn't a single number but varies with frequency. I'd guess you also won't get all the energy back due to soakage, which isn't a linear thing either. The result might also be manufacturer dependent, and probably aspect ratio dependent. Interesting measurement problem.

author: Berni
author_rank: Super Contributor
timestamp: June 29, 2018, 05:33:42 am
content: Yeah ESR is a big contributor but these discharges are so fast that internal inductance also matters. But in all cases shorting such a big capacitor will be very violent indeed. Its also pretty normal for large capacitors to build up a charge once discharged for a short period.Such high current discharges are certainly not healthy for the capacitor, but they survive them just fine. You likely need to put them trough a lot of these discharges before performance starts to degrade.I had a similar sized capacitor bank when experimenting with a coilgun and it worked great. But when things go wrong they go really wrong. For example i had a set of fairly beefy diodes in there to prevent inductive kickback, but on the fist fire of the coilgun the diodes blew into a short, so on the second shot all the current went straight trough the diodes and made them explode in a loud boom. What was left of the diodes was only the pins. To remedy that i added a bit of wire in series with the diodes to provide some resistance for the energy to dispate in. That worked to save the diodes but the kickback current was so large that it bent the neatly folded wire out apart after the first test shot.

author: CopperCone
author_rank: Super Contributor
timestamp: June 29, 2018, 01:54:57 pm
content: Ah yea i forgot to mention esl i should have just said are the usual parasitics skewed for large electrolytics due to electromechanical forces during discharge which i assume are highBut the big difference is the noticable dielectric soakage which also worried me.I want to work on protection circuits for capacitor banks. I intend to start with lower values but i suspected the nature of electrolytic capacitors the size of shampoo bottles is different.I may try making a pcb rogawski coil but i am still unsure of the significance of the feedback/ balance winding which would require 3 layers for signals and 2 for shield, which i cannot make at home, i can only do 2 layers kapton copper shield. I can make 3 boards and via stitch them together though lol. I might seems like a fun thing totry to make a 6 layer pcb at homeThis lack of ability to measure pulse currents is irritating. The best i have is a 500a tektronix probe but the bandwidth is like 1 or 5 khz. 500a is not enough, i at least want a rogawski coil for zoning the measurement. I need e field rejection more then accuracy or linarity. But thats the hard part.

author: Berni
author_rank: Super Contributor
timestamp: June 29, 2018, 03:20:24 pm
content: Well this building up a charge can happen in small capacitors too, but the fact that a small low voltage capacitor builds about a volt across its terminals is usually not all that concerning. When a soda can sized capacitor builds up 50V across it its quite a bit more concerning since its getting into potentially dangerous voltage territory and shorting one of these out could still give a little bit of a fireworks show.For this reason very big capacitors usually have bleeder resistors connected in parallel with them so that any residual charge slowly gets drawn off, yet are high value enough to just get a bit warm under normal operating voltages. And when such capacitors are taken out of the system and stored they often install a piece of wire across the terminals to make sure they won't build a charge in storage and shock someone who tried to move them.As for measuring your short circuit current the easiest way is to use a shunt resistor. You can buy very large screw terminal shunt resistors with a few miliOhm resistances. Or on the cheap you can just take a length of thick wire, add sense connections to each end, measure the resistance accurately with a good DMM in 4 terminal Ohm mode and then hook up the sense lines to the scope. Tho if you use copper wire you need to re-mesure its resistance if the temperature changes because copper has an awful electrical resistance temperature coefficient.

author: wraper
author_rank: Unknown
timestamp: June 29, 2018, 03:26:57 pm
content: Quote from: CopperCone on June 29, 2018, 01:38:16 amI would be more concerned to not shit your pants. It is destructive to capacitors, and with something that holds this much energy, whatever you'll use for shorting and terminals would at least partially melt and vaporize. It might be partial damage or even connection between capacitor inside (foil/paper roll) and terminals might explode internally.

author: CopperCone
author_rank: Super Contributor
timestamp: June 29, 2018, 03:58:56 pm
content: I did not want to use a shunt because i thought it might explode. I thought that i might be measuring current flow through a plasma channel. I dont know how to design aaccurate shunt for explosive peak currents.Also from my research topics about inudction heaters you might not get the highest peak currents connecting capacitors like that. I measured a significant distributed capacitance on a silver foil cap bank i built between two sheets of copper. They use a specific geometry for bus bars connecting a bunch of capacitors... That looked like corrugated roofing geometry.There is a diagram or link in one of my threads that shows a crude example of measured current in a bus bar connected capacitor bank and says how it can be done betterI would also like to attach some deflection gauges to the capacitor during discharge to measure its mechanical deformation if measurable to like 0.2 thousanths of an inch.My suspision is that there is significant mechanical force that can lead to aluminum strain and tearing. But i want realistic conditions for testing my circuits and real measurements for design purposes. I know no one cares commercially but i find it interesting so whatever.And for the baseline measurement i would like the lowest load impedance possible and highest peak currents, maybe there is room for a shunt past that point under more realistic circuit conditions with some wire or significant lenght bus bars, etc

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: June 29, 2018, 05:09:07 pm
content: Do a search onlaser discharge capacitor. You should find lots of stuff, though maybe not the depth you need.

author: Berni
author_rank: Super Contributor
timestamp: June 29, 2018, 05:42:22 pm
content: Yes this is exactly why you need a beefy very low resistance shunt. For the fun of it i tried hooking up some wire out of a CAT5 cable up to my coilgun and yes it explodes rather violently into a shower of sparks. A shunt for your application might look something like this:https://www.amazon.com/AMMETER-SHUNT-500-AMP-MILLIVOLT/dp/B005BHPG6KIt can handle 500A continuously without melting so it should handle even 5000A for a milisecond just fine(Or alternatively you can just use a length of 32mm2 copper wire as your resistor. Its really difficult to blow up like that, tho your connection points to it could start sparking if you don't use huge copper lugs to terminate it). You probably won't be able to get more than that out of your capacitors unless its something specifically designed for peak output current.Magnetic forces at these currents are indeed something to keep in mind. The thick cables involved in my coilgun would jump upon firing. But its not forces that would permanently bend bus bars or anything, but if there are significant runs of parallel cables it can be a good idea to tie them down.Oh and that video does not do it justice how violent this is. Sure there is the shower of sparks going across half the room but its also accompanied by a bang that is loud enough to make your ears ring, really it is the equivalent of setting off a firecracker.EDIT: By the way if you want peak current then its the high voltage film capacitors that you are after. They are the size of a briefcase and have ratings between 2 and 30 kV. The capacitance might seam tiny at only a few uF but they store a lot of energy while the high voltage doesn't really care about having super low resistance or inductance as it has the persistence to push trough it. There are the sort of capacitors that get you to >10kA peak currents and will not only kill you when you touch them but also leave cooked parts the bodypart in question scattered over the room as the water in them turning to steam causes them to explode from the inside out.

author: CopperCone
author_rank: Super Contributor
timestamp: June 29, 2018, 07:03:10 pm
content: Nah the objective is to determine what can happen to a circuit connected to a big filter cap and how to protect it and to get ideas of the measurements. I was wondering if the polarization can sort of act like a nonlinear drag force like conrad hoffman said.I do have those big film caps on my agenda though.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 29, 2018, 07:42:27 pm
content: Yes, the small signal equivalent circuit (ESR, ESL, C) is close enough.Tim

author: jmelson
author_rank: Super Contributor
timestamp: June 29, 2018, 08:36:03 pm
content: Quote from: CopperCone on June 29, 2018, 01:38:16 amOK, I hope this is for simulation/scientific exercise only. A decent electrolytic bank dead-shorted like that will deliver something like 100,000 A. You will need hearing protection, face masks and likely an arc-flash suit to actually do this.I have shorted out something like 3000 uF at 60 V and it sounded like a big pistol being fired in a small room.Jon

author: CopperCone
author_rank: Super Contributor
timestamp: June 29, 2018, 09:06:19 pm
content: I consider it destructive testing. I hate not knowing the specifics. A capacitor used for this purpose would be used, measured, and used for the same purpose only until it broke.This is why I made this thread. People are saying 5kA max, now you 100kA.This is why I want to measure this and know the specifics so I can know exactly what the ramification are of using big filter capacitor banks.You don't need all of that, you just need to make some kind of rig or power switch and hearing protection. The dangerous part is arming the switch/trigger. I don't intend to drop brooms on it, I would probobly use a pnumatic cylinder with a bronze head or some shit to bridge a bus bar screwed into the thing.I would also step around a corner to make sure fragmentation from a capacitor explosion can't hit me.

author: David Hess
author_rank: Super Contributor
timestamp: June 30, 2018, 02:07:17 pm
content: The aluminum strips which connect to the terminals inside of a big aluminum electrolytic capacitor can melt with a direct short.High voltage capacitor banks used in high energy physics can fail by exploding resulting in things like finger sized holes blasted into 1/2 inch thick aluminum bus bars.

author: CopperCone
author_rank: Super Contributor
timestamp: June 30, 2018, 02:22:04 pm
content: lol

author: CopperCone
author_rank: Super Contributor
timestamp: June 30, 2018, 02:29:04 pm
content: can they fail in such a way that the external connections are disconnected but there is still heavy charge in the capacitor that can explode like a time bomb? So you measure it 0V, but really its charged to quite a bit with some loose insulation that can cause it to blow up at any point? Like spark in one area, pressurize with plasma and short everything out?Maybe there should be 2 sets of terminals on the top and bottom of this thing for that reason since it is so powerful.A solution would be to monitor the bleed current I guess after a discharge to make sure it follows a decay rather then piecewising to 0. I never seen anyone do this before though?How does DA work? Does the impedance of the dielectric absorbed energy change over time (i.e. the series resistance is low at first right after discharge then it raises so you can drain it?)

author: raptor1956
author_rank: Frequent Contributor
timestamp: July 01, 2018, 03:51:02 am
content: A pro grade camera flash unit can output 100KW for 1/1000 second and the larger studio flash units (strobes) can do about 1MW and all use capacitors to provide that brief pulse of power.Brian

author: CopperCone
author_rank: Super Contributor
timestamp: July 01, 2018, 04:23:55 pm
content: So thats like 2500 Amps? Those caps run at like 400V right?

author: Wolfgang
author_rank: Super Contributor
timestamp: July 01, 2018, 06:19:25 pm
content: Hi, I had exactly the same effect on a 3kJ 350V capacitor bank. I tried to avoid polarity reversal by a 75A continuous fast diode. After a discharge experiment into a coil there was a loud boom, the diode was ripped out from the place where it was screwed onto, and what remained was just the leads with some screw terminals attached.The next try was a hockey puck diode rated ca. 2kA. This one survived so far.For a shrinking experiment I cascaded 5 of the banks above to a 1.5kV, 15kJ bank. Every single switch, even railroad thyristors rated for a few kA continuous, were completely destroyed after the first shot. The method that worked (unsatisfactorily) was a mechanical switch using copper bars clashed together. It did the trick, but also spot-welded the contacts.Any ideas to handle this better ?

author: David Hess
author_rank: Super Contributor
timestamp: July 01, 2018, 09:57:24 pm
content: At low voltages I think you are limited to mechanical switches. The big systems I know of closed the switch contacts using explosives. You might try a switch constructed like a starter solenoid for longer life.

author: CopperCone
author_rank: Super Contributor
timestamp: July 01, 2018, 10:51:54 pm
content: are those explosive powered switches meant for reuse?Are they pyrotechnic like a shotgun or do they use high explosives?

author: Marco
author_rank: Super Contributor
timestamp: July 01, 2018, 11:45:41 pm
content: What's the impedance of your coil? Are you sure you sure it's not the dI/dt killing the thyristors?

author: David Hess
author_rank: Super Contributor
timestamp: July 02, 2018, 03:32:57 am
content: Quote from: CopperCone on July 01, 2018, 10:51:54 pmThey use high explosives ... once. You could make something which uses a firearm primer and piston. Some high power circuit breakers use compressed air but isn't that to blow out the arc when tripped?Starter relays or at least good ones use a copper disk on the armature which slams into thick copper studs. The copper disk rotates on every activation so it lasts longer. They are also inexpensive because the same part was used on so many old cars.

author: Berni
author_rank: Super Contributor
timestamp: July 02, 2018, 05:25:03 am
content: Oh yes that 'mechanical switch' must have been pretty damn loud at those sort of energies. Coin shrinking also tends to use coils with only a few turns so currents are much higher than with something like a coilgun.Switching that in a well repeatable way is going to be tough indeed. I guess if you had enough of these hockey puck SCRs in parallel it would survive it. The switches used in power distribution to switch 100kV at massive powers tend to be multistage switches running in vacuum. There is a smaller switch that makes contact first to take the transient before the contacts of a bigger switch close without sparking to make the low resistance connection for the current.The Geek Group built Project Thumper. Its a U42 server rack filled to the top with capacitors meant to destroy things in spectacular ways. The switching mechanism used there is a piston that brings two beefy contacts together very quickly, but the trick is that the contacts don't quite touch. Because the capacitor bank has a lot of voltage that lets the contacts arc over, once the arc starts the massive current gets it very hot and that brings its resistance down to next to nothing. But since the contacts have not touched they don't weld. I would think that these contacts might need a bit of a resurfacing on a lathe after many operations tho, but im sure they are good for at least a few dozen operations between services.

author: Gyro
author_rank: Super Contributor
timestamp: July 02, 2018, 09:16:16 am
content: Quote from: David Hess on July 02, 2018, 03:32:57 amSome, even higher power circuit breakers use a blast ofHydrogento blow out the arc!

author: CopperCone
author_rank: Super Contributor
timestamp: July 02, 2018, 04:11:07 pm
content: Quote from: David Hess on July 02, 2018, 03:32:57 amIf they use high explosives i doubt anything else will work. A firearm will struggle for 1500m/s even with crazy barrel pressures while high explosive will clear 8000m/s easyIf you used a shaped charge lance or a explosively formed penetrator glob you can double that speed i think, but i dontknow how you would use a werid high pressure fluid metal phase used in weapons to bridge an electrical contact. Makes me wish i went to college in new mexico lol, they can probobly figure it outI think i would stick to pnumatics if i can.For some reason shooting plasma out of a lightgas gun to make a contact comes to mind but i am nut sure what benefits it would have. They can do like 20km/s with small masses, and slower ones can accelerate a few pounds to something like 8km/s. Might be safer then high explosives but sooo much more expensive. And the size of a van.

author: Marco
author_rank: Super Contributor
timestamp: July 02, 2018, 06:37:50 pm
content: Quote from: Berni on July 02, 2018, 05:25:03 amFor something which discharges in 10s of milliseconds maybe, for something which discharges in 10s of microseconds not a chance. They take too long to turn on (ignoring exotic variants).

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 02, 2018, 09:03:53 pm
content: Hockey pucks have been used for quarter shrinkers before.More in parallel would work, assuming you resolve the simultaneous turn-on and current sharing well. In fact this is true even if the devices are much slower than the intended, because the current draw is the sum of a bunch of slower things and therefore speed (dI/dt) is proportional to the number of units*.(*There is a clear exception to this, let's see if anyone catches it?)Tim

author: CopperCone
author_rank: Super Contributor
timestamp: July 02, 2018, 11:20:17 pm
content: well for a device that deforms metal what kind of time constant do you need since it is related to mechanical motion? Do you need a super crazy high peak?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 03, 2018, 12:47:14 am
content: What IS the time constant, anyway? Hmm...You have to get the material moving, simple enough. But the conversion from electrical energy to kinetic energy is very poor indeed. The conversion to joule heating is much more favorable (>50%).It should be fairly fast, since if it's slow, the force will never exceed yield, and the material doesn't go anywhere at all. All energy is dissipated in the material, coil, and radiation.If it depends upon the yield strength, then that's a pressure, which is also an energy density. It should depend on resistivity as well, since a lower resistance will have more force than otherwise. Also for bulk materials, a lower resistance gives a thinner skin depth, which puts more force in the surface (which causes an hourglass shaped deformation), versus in the bulk (where the force is distributed over more material -- though still most intense at the surface, so this should be a lower order effect, at least until resistivity is so high that the magnetic field isn't fully absorbed by the material at all).There also needs to be a scale factor, because this is a magnetic process, so the force is proportional to field (squared) and a length factor.Let's see. Field strength also gives a pressure directly (the Maxwell stress, σ = B^2 / (2 µ_0). That, pretty clearly, needs to be greater than the yield strength of the material, give or take how it's distributed (because the pressure won't be actually-zero at the ends of the workpiece), times a geometry factor.If you had superconductors, you could sustain the current (and force) forever (i.e., at DC), until yield is exceeded of course. (Incidentally, 7T contains an internal pressure about equivalent to a bottle of non-liquefied gas, i.e., a SCUBA tank, or a bottle of welding argon, say. Superconducting magnets go up to 20-30T, and are indeed nothing to trifle with.)That all seems to suggest the time constant comes from the material resistivities (work and coil). One limit due to workpiece size and skin effect, the other due to losses in the resonant (RLC) circuit.The exact waveform you should measure -- or hope for, anyway -- is a damped RLC response, except the L increases (and probably R as well) over time. So, a non-LTI system, which we can approximate as an LTI system because the change will be relatively small (<20%, until the coil or workpiece tear apart into fragments -- presumably, the shot is all but done by then, though).Why does L increase? Because 1. that's how the elements of the system are moving, and 2. that's where the work is going: it manifests as an increasing inductance, storing more energy than initially expected. The "stored" energy is actually transformed into mechanical energy, in part. Note that the inductance does still increase, so the magnetic energy requirement also goes up; this will be wasted during ring-down (or fragmentation).You would want the waveform to peak during the expansion phase, so that real work can be done (work = force * distance), which gives another time constant, a mechanical one, and probably the most limiting one (because mechanical motion is so much slower than most anything electrical). This will make the method impractical beyond a certain size * resistivity limit.Which... you're welcome to believe I looked at this first and wrote everything after, or that this post is in fact in chronological order. But the above seems to be quite on the nose:http://english.pstproducts.com/empt%20forming%20welding%20crimping%20and%20cutting.pdfI was about to say, ordinary-sized objects, in steel, would be about the limit of practical application. I wanted to check if that's the case. Well, it looks like it is, so that's neat.Also, they have a toy waveform there, which nicely shows the mechanical process. I suppose, as long as the force greatly exceeds yield, the material will accelerate, and soon after, pick up enough velocity to draw useful work from the coil. Then, as long as this is done faster than the skin effect and size limits, the efficiency should be about the same, somewhat independent of the coil turns and capacitor value (given that C*V^2, i.e. the initial energy, is enough for the job). That is, it doesn't matter if the resonant circuit is ringing, or goes "thud", so long as the mechanical energy is supplied.Note that, in the example they give, things are very fast indeed. To travel a few mm in 10µs, requires a velocity of 100s m/s. Presumably, it's very easy to exceed the speed of sound here, which will give the additional phenomena that: air in the gap is compressed supersonically, and heated; the high temperature and velocity gas is mostly ejected (some may get trapped in pockets and voids between the metals, if the surfaces aren't uniform; apparently this isn't much of a problem, as they suggest defect-free voids are achievable); and, between that, and the surfaces slapping together with great violence and shear, the surfaces are stirred up, oxides ejected, and the parts can essentially become cold-welded together (much as  explosive forming does).So, this is very much on the same order as explosive forming as such, and can potentially be faster than chemical explosives, because propagation velocity is limited by the speed of light, or perhaps more to the point, the maximum velocity of electrons in a spark (see: Z Machine). So, uh, much greater velocity might be achievable, but because nothing can move that fast, you're either vaporizing material off (e.g., exploding bridgewires?), or turning it to plasma (of ever-greater ionization degree, with essentially no upper limit as you push into the megakelvins and generate x-rays).Oh, and yeah, needless to say, the Z-Machine doesn't use SCRs; I don't know what they use, actually. Custom ignitrons? Looks like... sort of, just fancier. Laser triggered gas switches, I guess?Tim

author: Berni
author_rank: Super Contributor
timestamp: July 03, 2018, 05:16:13 am
content: That's an interesting article. Its basically a useful application of those electromagnetic ring launcher demonstrations. Must need some rather beefy equipment to run that.Oh and from the old days there are trigerable spark gaps. They call them a Trigatron:https://en.wikipedia.org/wiki/TrigatronIts basically a high voltage 'SCR' from back in the vacum tube days. Wiki claims there are such devices for mega amper currents, but good luck finding where to buy one of these dinosaurs.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 03, 2018, 06:41:22 pm
content: Oh yeah, when I said "ignitron" earlier, I meant trigatron -- the former is a mercury thyratron, the latter is a triggered spark gap.Tim

author: CopperCone
author_rank: Super Contributor
timestamp: July 03, 2018, 06:43:10 pm
content: Yes I made a small triagtron that is in limbo due to money right now. I described it some where on the forum.

author: Marco
author_rank: Super Contributor
timestamp: July 03, 2018, 06:58:47 pm
content: How much energy do you actually lose with the simple open air sparkgap triggered by moving one round head bolt to another? If it's say 50% for a coin shrinker, just eat it.

author: CopperCone
author_rank: Super Contributor
timestamp: July 03, 2018, 07:11:20 pm
content: There is a voltage drop on the arc. I wonder if you can measure thermal losses with a fast gas calorimiter.Or just submerge the entire spark gap into a calorimiter. It would have to be a really good one or your arc would need to be really big though.Otherwise you measure the voltage drop and the current I guess and integrate? Guess what you need for that, rogawski coil.

author: David Hess
author_rank: Super Contributor
timestamp: July 03, 2018, 10:46:15 pm
content: I would need to reread some of my thyristor application notes but as I recall, they have some switching limits related to turn-on duration. For instance triggering them with insufficient gate current increases their turn-on time and lowers their maximum rating due to uneven conduction causing uneven heating of the junction.So what I might try is shaping the pulse from the capacitor bank through some inductance (which saturates) or a transmission line such that the SCR is fully turned on before peak current is reached.

author: 3roomlab
author_rank: Frequent Contributor
timestamp: July 06, 2018, 03:51:54 am
content: this is a string of 2 interesting random finds from google (images). i was not specifically looking for cap related stuff.and then this came upi think i was quite familiar with the L x 2 ^ whatever arrhenius equation, but this? it further multiplies into "un-used" voltage, and "ripple current" tolerance? the equation is supplied by SAMXON and has a IPC logo (IPC approved method? IPC?). which from a little bit of spreadsheet fiddling, it easily adds an additional multiple of roughly (2^7) or x128 to the original number of hours. hmmm?is this common (as in further life extension by adding voltage/current tolerance)? the slides appear to be dated from 2012 from somekind of SAMXON/IPC presentation paper. and is related to IPC9592is it that all manufacturers have their own "flavor" of how to calculate capacitor lifespans? which then makes lifespan specifications (and likely ripple current rating?) to be highly unreliable?

author: Berni
author_rank: Super Contributor
timestamp: July 06, 2018, 05:40:01 am
content: I never seen a electrolytic with termocuple sticking out of it, neat trick.For huge SCRs i hear its pretty common to really give it a real good kick at the gate to switch them. As in discharging a smaller capacitor directly into its gate and similar rough handling that you would expect would kill it. Guessing that's how they make it turn on fast enough to avoid that uneven turning on problem you mentioned.Oh and the losses in the sparkgap might be comparable to the losses along the cables too. With such massive currents even a tiny bit of resistance will make heat.

author: Wolfgang
author_rank: Super Contributor
timestamp: July 11, 2018, 07:54:22 pm
content: Hi,I am NOT sure what killed the thyristors. It could be dI/dt, or just the mere peak current, or both. Another candidate is voltage reversal.There are some IXYS pulse thyristors available, but for a steep price. I did not try those yet.

author: Wolfgang
author_rank: Super Contributor
timestamp: July 11, 2018, 08:04:57 pm
content: do you have a reference of somebody who has used hockey pucks for am shrinker ?