output from transformer is coming not as expected - Page 1
Forum section: electronics / beginners

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 04, 2017, 04:07:43 pm
content: I have made 2 psu 48v 5a each using 2, 12-0-12v 5A transformerI have connected those psu in parallel so that i can get double current, i.e, 10ampMy load is brushless dc motor which can draw current upto 13ampsBut the problem here isWhen i am connecting the psu with controller and motorCurrent draw goes to max 1.5 amp starting from 0.5 ampI have connected the terminals of multimeter in series to the +ve wire of psu(incase if someone finds me wrong here for checking the current)And because of less current the voltage comes down drastically as soon as i use throttle to run the motor fasterPlz help,Why the output current so low,How can i draw 10amps as i am using 2 5amp transformer in parallelThanksthe

author: schmitt trigger
author_rank: Super Contributor
timestamp: October 04, 2017, 04:18:35 pm
content: the motor current with a motion-less rotor, is several times higher than the full load current.So it could be loading down your supplies.This plus the fact that two supplies in parallel, even if they are identical (which you have NOT shown), will never share the load current equally. Unless ballasting or an active load controller is employed.

author: wraper
author_rank: Unknown
timestamp: October 04, 2017, 04:24:01 pm
content: PSU schematic please. If they are regulated PSUs, connecting in parallel likely will cause issues like oscillation unless PSUs are made to cope with that. You write about current without measuring actual voltage.

author: rstofer
author_rank: Super Contributor
timestamp: October 04, 2017, 04:29:52 pm
content: What is the open circuit voltage of each power supply individually? What is the voltage when they are in parallel.I'm missing something because a 12-0-12 transformer isn't going to deliver 48 volts. No doubt I am just not comprehending what is going on.Figure the motor draws 6x full load current at startup. If you want the right answer, measure the winding resistance and use that in Ohm's Law. It's often hard to get the resistance of motor winding because it is so small. Some DMMs can do it...

author: BenKenobi
author_rank: Regular Contributor
timestamp: October 04, 2017, 05:37:05 pm
content: I find this description confusing how - and where - are you trying to measure this, how exactly are you connecting the motor ?what are you using as an 'inverter' - i.e. an ESC you can't power a brushless motor directly with DC and I wouldn't recommend putting AC across it.In any event to measure current on a brushless motor you measure the input to the motor controller not the motor feeds since these get switched to simulate 'brushes'.Are you running the motor with a load would be the next question - load the spindle down with friction and see what the current does.

author: schmitt trigger
author_rank: Super Contributor
timestamp: October 04, 2017, 06:08:57 pm
content: Quote from: rstofer on October 04, 2017, 04:29:52 pmI had read the OP quickly and did not pay much attention to the actual values,But.......after re-reading the original post, count me in as another person that doesn't understand what is going on.

author: BenKenobi
author_rank: Regular Contributor
timestamp: October 04, 2017, 06:21:02 pm
content: I kind of did the same, I'm thinking now that the motor is running without a load so it's bound to draw below rated current - which is a maximum rating not a target.I'm guessing also that there are two 12 0 12 in series so that does provide 48V, I don't know many ESC's that can handle this - 44V DC is about the biggest I know of that is off the shelf (at reasonable cost).Transformers in series - question to OP - are you sure these are 'phased' correctly and both identical. In any event two transformers in series doubles the voltage NOT the current though - the most you can draw is 5A.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 05, 2017, 11:52:09 am
content: I have attached circuit diagram of one psuI have made two psu like this then connected it in parallelI am using controller to run the brushless dc motor

author: BenKenobi
author_rank: Regular Contributor
timestamp: October 05, 2017, 12:35:24 pm
content: The output is in series not parallel. The most current you can pull is the lowest TX amps rating.http://engineering.electrical-equipment.org/forum/general-discussion/difference-between-series-parallel-transformerYou should be linking before the rectifiers and use a single rectifier too.

author: tooki
author_rank: Super Contributor
timestamp: October 05, 2017, 12:43:59 pm
content: Quote from: BenKenobi on October 05, 2017, 12:35:24 pmThe schematic is ofonePSU. He said he put two of these PSUs in parallel.

author: BenKenobi
author_rank: Regular Contributor
timestamp: October 05, 2017, 12:52:07 pm
content: My bad -but still don't understand why he's rectifying both TX's - I'm thinking there is a phasing issue here - in any event just because a motor is rated at 13 amps doesn't mean it will pull 13 amps - it needs a load, the measurement has to be before the motor controller.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 05, 2017, 03:56:57 pm
content: So do you suggest me to use one rectifier for two transformers?And i have a motor controller with a throttle to control the motorAs per my testingI get 50V at the startingBut as soon as i use throttle to speed up the motor(which will conclude controller will try to fetch more current)The voltage rating goes down till 37v and stops as controller doesn't supply power to motor below that voltage ratingI have checked current and i have got max 1.5 ampsThats the main issure despite of using 10amp psuPlz suggest me and do tell me where am i going wrongThanks

author: BenKenobi
author_rank: Regular Contributor
timestamp: October 05, 2017, 04:17:54 pm
content: How did you confirm the phasing on the transformers ? i.e. are the sides of highest potential 'aligned'https://www.linkedin.com/pulse/transformer-polarity-mike-hennesey/I think that by putting the TX's in series and using a single rectifier will reduce complexity for sure, you only need to do what you show if you want to tap 24VDC for some reason, the voltage shouldn't decay that much if at all - what are you using as a controller - I'm guessing some kind of ESC - many of these need to be programmed they generally aren't plug and play.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 05, 2017, 07:13:05 pm
content: Well i have purchased a kitI have got motor , controller and throttle with itWhat do you mean by phasing sry but i didn't get itWhat do you suggest what should be the noble approach to meet my final requirementsAs i want to give output of 48v 10am which is said to be possible with the transformer i haveThanks

author: BenKenobi
author_rank: Regular Contributor
timestamp: October 05, 2017, 08:33:16 pm
content: Been looking for something to explain. Take a look at the vid in the link, notice what happens when one transformer isn't doing what you think, also notice what happens if you get the wires crossed on the TX outputs. I'm not sure whether the rectifiers are there to try and overcome some of this but it's a messy way of doing things, you'd have been better off with a single 50V transformer and a single rectifier, but you could still go single rectifier by moving your series link to the transformer side of the rectifier then you only need one - depending what your diodes are rated for (I assume you have diodes and not a package).Beyond that need to know much more about this motor and its associated controller - brushless motor controllers are quite complexor (this is basic but explains brushless control very well)

author: Damianos
author_rank: Frequent Contributor
timestamp: October 06, 2017, 11:57:03 am
content: Quote from: VickySalunkhe on October 05, 2017, 11:52:09 amSo you there is a series and parallel combination of four power supplies.To take the maximum of the above, ALL the secondary coils of the transformers have to be connected IN-PHASE, except if there is really huge capacitance on each one.By the way, how much capacitance is on the filters? I see something like 2.2M?, that does not make sense.Hope that you know and understand about the hazards in what you are doing! An exploding capacitor is not an enjoyable experience!

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 06, 2017, 04:38:19 pm
content: So do you suggest me to increase the capacitorAnd if yes how much ?As you can see i have four transformerAt the very first of building this psuI was using 13.2 mF cap (6 , 2.2mF cap in parallel)But due to less current output i thought to remove some of the capAs i got to know cap stops the current flow once they are chargedBut that doesn't seem to make a lot of changes.I have some doubtsWhat do you mean by in phase connection?Can i connect the transformer in series and parallel and then give that supply to bridge rectifierWill it be safe?Thanks

author: tooki
author_rank: Super Contributor
timestamp: October 06, 2017, 04:44:19 pm
content: If you are confusing what capacitors (measured in Farads) and resistors (measured in ohms) are, you are NOT yet ready to be building this thing!! You should be nowhere near mains wiring yet!!!!!

author: BenKenobi
author_rank: Regular Contributor
timestamp: October 06, 2017, 05:21:18 pm
content: QuoteI sense that you really need to study the basics of electricity / electronics - understand how AC works and how transformers 'transform' it.Some basic ohms Ohm’s law and Joule’s law isn't going to hurt alongside equivalent resistance and capacitance, Kirchhoff’s current and voltage Laws - sorry but electronics is something of a mathematical sport.For example your 'capacitor' is nothing to do with current - that's a hint - go find out why it is there and how to calculate what size it needs to be - go and study full wave rectification to find this out.Whilst power supplies are amongst the first things that many build they require you to understand a lot of basic theory to build a good one. Dave did a really good series on power supply building

author: Damianos
author_rank: Frequent Contributor
timestamp: October 07, 2017, 05:00:16 pm
content: Quote from: VickySalunkhe on October 06, 2017, 04:38:19 pmNo, not exactly!The only advisement, that I can give to you, is to stop this project until you acquire some knowledge and understanding, at least on the basics, as already mentioned by others.It seems that you cannot see the dangers that exist in what you are doing!QuoteI see, but...QuoteI don't know if a thing like this exists!Quote? ? ?QuoteThis is important, at least, when combining coils...It's one more indication of missing knowledge and understanding.QuoteOf course yes! But, the way of doing that, will give as result:- what you want to have- absolutely nothing- damages to surroundings from transients- more or less serious injuries up to death- put in fire your houseQuoteAs it seems, no!QuoteYou are welcome!Start studying the basics, there are people here that will help you by answering specific questions. It's a little difficult to design and implement a Formula-1 vehicle, if you don't know the properties of the wheel!

author: IanB
author_rank: Super Contributor
timestamp: October 07, 2017, 05:10:16 pm
content: Quote from: BenKenobi on October 05, 2017, 04:17:54 pmQuote from: Damianos on October 06, 2017, 11:57:03 amPhasing of transformer windings doesn't matter if the outputs are rectified before they connected in series/parallel.Why are people giving the OP confusing information?Phasing only matters if you are connecting the windings together in AC mode before rectification.

author: Audioguru
author_rank: Super Contributor
timestamp: October 07, 2017, 10:35:45 pm
content: The transformers are 24V each. The peak voltage is 24 x 1.414= 33.9V and the bridge rectifier reduces it to 31.9V that is filtered by the capacitor. Two in series provide 63.8VDC, not 50V.Each transformer is rated for 24V at 5A which is 120VA. But when rectified the voltage is 33.9V so the maximum allowed output current is 120VA/33.9V= 3.54A DC.What is 2.2M? If it is 2200uF then it will produce a lot of ripple voltage when the high current is drawn which will reduce the average output voltage. Use capacitors with much more capacitance.

author: Brumby
author_rank: Unknown
timestamp: October 07, 2017, 11:02:10 pm
content: Quote from: IanB on October 07, 2017, 05:10:16 pmI was thinking this as well.With the original layout from the OP, there was no problem with phasing - None, Zero, Zilch!!! Yet we have had someone throw this into the conversation and then others jump on the bandwagon. There is only ONE benefit from paralleling the transformers - and that is to save a voltage drop across a couple of diodes. For the voltages under discussion, that is not a big deal.SO ... rather than confuse this person with details that are essentially irrelevant, how about we forget all about stuffing around with transformers, revert back to their original design and discuss the real problems - starting with their basic lack of knowledge. (Please - let's not do transformer phasing just yet.)As far as the OP's ability to work with mains is concerned - I share the concern ... to a point. There is not a lot to go wrong if they understand which side of a transformer is the primary and connect it to the mains appropriately.Why do people continue to want to display their "knowledge" and confusing an already challenged person instead of paying attention to the real issues and looking at actually helping them?

author: Damianos
author_rank: Frequent Contributor
timestamp: October 08, 2017, 07:05:48 am
content: Let's for a moment we remove the capacitors from the circuit. What will be the maximum (peak) voltage at the output?Now let's connect them again and find the maximum output voltage. What about the maximum (peak) voltage of the ripple? In this case it is needed to do it twice, without a load and with a "heavy enough load", that represents the motor.If we do the above for both connections (in-phase and anti-phase), in paper, using a simulator or doing it in the lab and take the results, we can start thinking about the behavior of the motor in each case.Similarly we can do it for the availability of current, that we can draw, without "zeroing" the output voltage...As the voltage is peaking in higher value the motor has the chance to start rotating, producing back-EMF, reducing the loading ... ...Here, of course, the behavior of the controller has a role...QuoteBefore you comment, try to read the entire sentence!If there is not enough capacitance, to "support" the loading, then the voltage maybe drop up to half of what is expected!I don't thing that a capacitor of 2.2 milli- or mega- Ohm can do that!That comment is really vague! I did not tried to "improve" it, because, in the continuance of the discussion, appeared things that, in my opinion, show that the experimenter is missing basic knowledge and he is not in a position to understand what is doing.EDIT: The mentioned comment, by me, is not only vague but it is ... <put here what you wish!>!

author: IanB
author_rank: Super Contributor
timestamp: October 08, 2017, 07:17:35 am
content: Quote from: Damianos on October 08, 2017, 07:05:48 amIn phase or anti-phase is irrelevant, because in the circuit diagram the transformer outputs are DC rectified.QuoteOnce more, the capacitors have nothing to do with it. The transformer outputs have been full wave rectified before being connected, therefore phasing is irrelevant. Phasing is irrelevant if there are smoothing capacitors and phasing is irrelevant if there are no smoothing capacitors. We are talking about DC.So can we please stop confusing the OP with comments about phase?

author: Damianos
author_rank: Frequent Contributor
timestamp: October 08, 2017, 07:28:02 am
content: Quote from: Brumby on October 07, 2017, 11:02:10 pmIf your knowledge and experience says that overheating a capacitor, by ripple current, is safe...And that "the low load-current is the reason of the voltage drop", is an indication of understanding things.I have to disagree!For the rest I tried to explain...

author: Damianos
author_rank: Frequent Contributor
timestamp: October 08, 2017, 07:51:29 am
content: Quote from: IanB on October 08, 2017, 07:17:35 amSuddenly, by reading this, I had a flash and my mind detached! I don't know how and what happened! Maybe I need some relax. My mind was sticked with other things and I confused myself...The one that for sure I have to do is to go back and "repair" my comments...If anyone have spotted any other stupid thinking by me, let me know to try to correct that.Thanks for your patience and tolerance!

author: BenKenobi
author_rank: Regular Contributor
timestamp: October 08, 2017, 10:22:00 am
content: Sometimes the novice or trainee is not best served by providing the answer - but being led too the answer, to understand how and why things should work is the only way to know why they don't. I've trained many engineers and sometimes they just need to be made to think, they learn nothing from being given the answer on a silver platter constantly, it's a process whereby they read, they clarify, they gain understanding.The use of full wave rectification in this manner is not efficient, to understand rectifiers and the implications of their use you must first understand AC, to understand the output from rectifiers and the purpose of the 11 ohm 'capacitor' and DC side requires you to know what the limits and capabilities of the load are.Either way I stand by my remarks there is no way even two of these PSU's are going to provide 13 amps DC @ 48V - the builder needs to understand why.

author: Brumby
author_rank: Unknown
timestamp: October 08, 2017, 11:39:09 am
content: Quote from: Damianos on October 08, 2017, 07:28:02 amWhat on Earth are you talking about?

author: Brumby
author_rank: Unknown
timestamp: October 08, 2017, 12:26:09 pm
content: Quote from: BenKenobi on October 08, 2017, 10:22:00 amDid you ever "train" someone thousands of miles away via teletype? Because that's what is what you are trying to do here.The OP has presented a schematic for a very basic power supply, which should work. (Before you jump in here ... read on)QuoteMaybe ... but efficiency isn't the key issue here.QuoteFor this exercise? Please, NO. The diodes are there, connected properly. That's all that is neededforthisexercise.QuoteThat is just a confusing group of words.The only thing that concerns me is that 11 ohm capacitor thing. There is a big knowledge gap there.QuoteYou need to pay more attention to the information that has been supplied....Quote from: VickySalunkhe on October 04, 2017, 04:07:43 pmUpto.... keep reading.Quote10 Amps ..... the OP only wants 10 Amps - which is not beyond the realms of possibility with the supplies built in the configuration presented.So - if you want to challenge something, get the facts right first - please - otherwise you are just speculating. If you keep guessing without checking the basis of your comments are accurate, you aren't going to do anything but confuse the heck out of the OP ... who is already struggling with what has been posted here....and as far as the 13 amps is concerned - it IS possible for the OP's original system to supply 13 amps ... for a very short time.There is clearly something going on here - but nobody has obtained any information that can actually make definitive statements about what that is.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 08, 2017, 03:16:22 pm
content: By connecting the 2 transformer in series i am getting 52v after the bridge rectifierIn india its rare to find 15MF cap so i am using 6 , 2.2MF cap in parallel is that okayBut the problem is still unknown current drawn is max 1.5amp by using 4 transformer connected in series and parallel to achieve 52v 10ABut getting 52v 1.5A only

author: BenKenobi
author_rank: Regular Contributor
timestamp: October 08, 2017, 03:20:10 pm
content: So Brumby how about you step in - instead of just posting to berate those that do try to support.I'm done here

author: IanB
author_rank: Super Contributor
timestamp: October 08, 2017, 04:13:40 pm
content: Quote from: VickySalunkhe on October 08, 2017, 03:16:22 pmYou've got to break the problem down, simplify things and test step by step.First of all, take away the capacitors and test your system with a simple resistive load. See what current, voltage and power you can get just with that setup.You have a nominal 48 V supply. You need a load that can draw up to 10 amps from it. That requires a low value, high power resistor. Let's see if we can improvise. Do you have an electric kettle, 3000 W preferably? That will have a resistance of 3000^2/240 = 19 ohms. If you put that across a 48 V supply you should draw a current of about 48/19 = 2.5 A. Can you try that and see if you do in fact get a current of about 2.5 A? And does the voltage stay up around 48 V when you do so? (And of course, make sure there is water in the kettle when you make the test, so it doesn't overheat and trip the thermal fuse.)Make a test like that and get back to us.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 08, 2017, 04:47:38 pm
content: First of all Thanks everyoneI think too much confusion has been created in this post since it startedSo I'll clear out what i have tried and what is the requirement.I have made 2 psu 52v 5amp eachUsing 4 transformer of 12-0-12 v 5amp transformerCIRCUIT DIAGRAM IS ATTACHEDi have connected those 2 psu in parallel hoping that I'll get 10amp outputBut not succeed in it (GOT 1.5 A MAX) by connecting the loadI have got brushless dc motor which is connected to controller and a throttle to speed up the motorController can draw upto 13AmpsI have connected the single psu with Multimeter with no load to check currentDIAGRAM ATTACHEDi have a strong feeling what i have done to check current is inappropriate and dangerousBut just telling you what i have triedI got 8.6amp from single psuI have got readings while connecting the psu with motorAt no throttle i was getting 52V but as soon as i started using throttle the voltage started dropping and went down to 37V and tested currentAt no throttle current was 0.5 amp and at full throttle current was 1.5ampThis time i have tested current by connecting the multimeter is series with +ve wire(correct way)Now the real problemI am expecting 10amp current draw from the psu but not able to get it and voltage is dropping drastically as i increase throttleI would like to know should i connect fuse in the circuit to prevent and dangerous situationI have got 10amp fuse and 500ma fuseAnd as i am using basic multimeter which has no fuse would it be beneficial if i connect a fuse with the red leadTo prevent the multimeter from problem?I don't have the kettle so I'll not be able to test it like you suggested.Any other way you suggest to check current with no actual load?OrShall i test it using resistor lower than 15ohm so that i can get current more than 3.3ampThanks

author: IanB
author_rank: Super Contributor
timestamp: October 08, 2017, 05:32:02 pm
content: Quote from: VickySalunkhe on October 08, 2017, 04:47:38 pmIt seems like you connected the multimeter in the current range directly across the output of the power supply?Yes, this is the wrong way to do it. It is very inappropriate.But here's the thing. If you had a properly working power supply, the multimeter should have gone way off scale and blown the fuse. If there is no fuse, the multimeter should have started smoking and might have caught fire. You are lucky that didn't happen.However, the fact that you didn't smoke your meter tells us your power supply is not working properly.I think you should first test the transformers to see if they can really provide 5 A at 24 V, without any rectifiers or capacitors. You need to get a load from somewhere to test them with. How about car headlight bulbs? They will be typically 12 V and 50-60 W. Put two of them in series on a transformer and measure the current and voltage. Is it what it should be?Next, put the rectifier after the transformer and try again. Do you still get the expected voltage and current?

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 08, 2017, 06:11:56 pm
content: Could you plz suggest me any other way of testing itAs availability of load which runs on 12 or 24v with 100w power rating doesn't seem to be available with me.

author: IanB
author_rank: Super Contributor
timestamp: October 08, 2017, 06:27:09 pm
content: If you wish to test a power supply, there is no other way than to use a testing load.You have presumably purchased expensive transformers and rectifiers and capacitors. I am not sure why you cannot purchase some automotive bulbs to test with?Another way it to get a very long length of thin steel wire with a resistance of about 5 ohms and use that. Since it will get hot you may wish to submerge it in a bucket of water.

author: Damianos
author_rank: Frequent Contributor
timestamp: October 08, 2017, 06:27:19 pm
content: The 52V does not match with the voltages of the transformers. Without load it has to be at least ten volts higher.What are the real characteristics of the transformers?How are connected the primaries of the transformers?What types of rectifiers are used?...Is possible to present any photos of the construction?

author: Brumby
author_rank: Unknown
timestamp: October 09, 2017, 03:23:52 am
content: Quote from: BenKenobi on October 08, 2017, 03:20:10 pmI have in the past - and will continue to do so .... so long as I am not adding to the confusion.QuoteI don't mean to berate - I only want to point out when certain actions are less than helpful. It is easy for people with specific knowledge to want to "share" it - even when doing so is just adding to the whirlpool which many beginners are already struggling with.Any such comments of mine were aimed at helping the OP - not pandering to someone's ego.

author: Brumby
author_rank: Unknown
timestamp: October 09, 2017, 03:25:54 am
content: Quote from: Damianos on October 08, 2017, 06:27:19 pmThis is better. Asking questions - and more importantly -relevantquestions.

author: Brumby
author_rank: Unknown
timestamp: October 09, 2017, 03:59:19 am
content: An exercise forVickySalunkhe...* You say the output of your power supplies is 52V without any load connected.* You say you have a 15 ohm resistor. What power rating is this resistor? Can you provide a photo of it? If it is at least several watts, then try the test below.If it is not, then try to find a load resistor that has high power capacity - so it won't burn up during this test. I have a 27 ohm resistor rated to 1800W. It's an element from an old electric jug - and 27 ohms is a value that would still be useful for this test...The Test:1. Measure the resistance of the load resistor and make a note.2. Power upone halfof your supply that will give you the 52V output (disconnect the output from the other half)3. Connect your meter to this output and confirm this voltage. Make a note of the exact reading.4. With the supply still on and the meter still connected, briefly connect the load resistor across the output of the supply. DO NOT keep it connected for more than a second or two as it will heat up very quickly. While it is connected, make a note of the voltage on the meter.Tell us what the two voltage readings are and the value of the resistance. We can work out a couple of things from that.If you like, you can perform the exact same test on the other half of the supply and give us those numbers as well. In fact, it is a good idea if you do.Now I can hear murmurings about the fact that the resistance is going to be affected by the heating - but for this exercise, I am looking at getting some "ball park" calculations that might help guide further investigations.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 09, 2017, 01:28:33 pm
content: Sir first of all let me clear some stuff.I get 52v output without load and with load also(when throttle is at ideal position)I don't have the resistor i was thinking to buy oneIt's hard to find resistor of that much wattage rating around here.Can i try the method IanB suggested?I.e, connect a steel wire whose resistance should be near to 5ohmThen connect it to the psu and leave that steel wire in water (as wire will get hot)If i can try this, Can i try with a long copper wire as it will have resistance too, i have got 70m of wire with me.And i will try to bring you the readings asapThanks

author: Audioguru
author_rank: Super Contributor
timestamp: October 09, 2017, 01:56:52 pm
content: The DC voltage is too low and is full of ripple because the capacitors are probably 2.2uF instead of 2200uF. He wrote 2.2mF that does not say how many microfarads.but with no load the voltage should be about 66VDC.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 09, 2017, 03:56:22 pm
content: It's 2.2mFi.e, 2200ufI have given all the values by checking it thriceI have used 6 such cap in parallel i.e, 2200 * 6 = 13200uf or 13.2mFAnd i have also tried by connecting only 1 cap i.e, 2200uf or 2.2mFBut this both combination doesn't seem to make a diff more than a volt and current

author: Ian.M
author_rank: Super Contributor
timestamp: October 09, 2017, 05:03:27 pm
content: Take a look at the Hammond TransformersDesign Guide for Rectifier UseThe circuit configuration you are using is shown there as 'FULLWAVE BRIDGE Capacitor Input Load', and the maximum DC current you can draw is 62% of the RMS AC current, so your 12-0-12 5A transformer secondaries are only good for 3.1A DC (continuous rating) after the bridge rectifier and reservoir capacitor.I'm assuming your transformer ratings are correct but that's yet to be confirmed by a load test as suggested by Brumby.Calculating the required value of the reservoir capacitor for a particular application gets quite complex - it directly affects the amplitude of the ripple on the DC output, from Q=CV. As a rough approximation, since you are in a country with a 50Hz mains supply, the capacitor has to hold the output voltage up for 10ms between peaks of the rectified waveform so the peak to trough ripple will be about (Iload*10ms)/C volts. A rough rule of thumb, suitable for many applications is to use 2000uF per amp of load current, which gives about 5V ripple (actually a little less due to the conduction angle of the diodes in the bridge reducing the time the capacitor has to hold the voltage up for). The capacitors used need to be able to handle the ripple current. This is a PITA to calculate without using a simulator as it involves determining the RMS of a non-sinusoidal waveform, but if you take it as 4/3 the DC load current its near enough. Using too much reservoir capacitance is problematic - you risk exceeding the surge rating of your bridge rectifier diodes and may blow fuses on the secondary side of the transformer or trip over-current protection on the primary side. Worst case, you may need a sequenced soft start circuit that limits the inrush current into the primary, and keeps the load disconnected until the reservoir capacitor is fully charged.Transformers can handle large current overloads for a short time, a factor of two for under a second isn't usually a problem if you have sized your bridge rectifier and reservoir caps to cope with the surge, so done right, your transformers in series-parallel,if each is actually rated for 5A RMS (120VA), should be good for 6A running and a 12A startup surge.

author: Brumby
author_rank: Unknown
timestamp: October 09, 2017, 10:28:28 pm
content: Quote from: VickySalunkhe on October 09, 2017, 01:28:33 pmThis is clearQuoteThis seems strange. When there is a load placed on an unregulated supply, we would expect a voltage drop - but that does depend on what the load is and how much current it will draw. When you say "when throttle is at ideal position" - it does not tell us a lot, since we do not know exactly what the load is. Using a fixed resistor value and the voltage that is across it allows us to make accurate current measurements and perform some meaningful calculations in determining the capabilities of the power supply.QuoteThe "resistor" I was talking about is an old-fashioned electric jug element. Do you have them in your area? They are mains rated with high power capability and if fitted to a jug, can be water cooled - this is perfect for this type of testing. (Edit: While I don't believe it would be a problem, the actual resistance of such a jug element is important in choosing an appropriate configuration of your individual supplies. See comment below. **)But, there are other alternatives.....QuoteYou can certainly do this - but if you do, please make note of the following.....** If your 'long wire' resistance is less than 10 ohms, youmustdo the test I suggested with either:A. Both halves of the supply (all 4 sections) connected as you have shown in your complete supply-or-B. Separate all four sections and do an individual test on each oneIf your 'long wire' resistance is less than 5 ohms, then it is too low to test anything.These values are for testing the supplies at the maximum load condition you have specified - but a resistance a bit higher can still give us very useful information. If your "long wire" resistor is 7, 12 or 19 ohms (under the rules above), then the results are still quite useful - we just need to know its resistance as accurately as you can provide.

author: Damianos
author_rank: Frequent Contributor
timestamp: October 10, 2017, 07:08:11 am
content: Quote from: Damianos on October 08, 2017, 06:27:19 pmSome additional points:What is the secondary voltage of each transformer (measured)?What is the output voltage of each one of the four supplies? Independently, without connections between them and without any load.Do the capacitors keep the voltage, when the mains is disconnected?What is the voltage of each one when they are connected together? Again, without load....Leave it running for a while without load. Is there any acoustic noise from the transformers or any other component?After few minutes, disconnect the mains and check if anything has warmed up. Normally, all the parts must be at environment temperature. Use a thermometer, if available, otherwise be careful of what you are touching....What are the specifications of the motor's controller?Is the measured current stable or is it pulsing?

author: Brumby
author_rank: Unknown
timestamp: October 10, 2017, 01:20:44 pm
content: Quote from: Damianos on October 10, 2017, 07:08:11 amThose are all reasonable questions - but there are a lot of them.I would suggest the OP does the load test with the wire resistor and supply that information first. That way, we should get a better idea of which particular questions should be asked next.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 10, 2017, 05:28:27 pm
content: Sry but due to some confusion i told you the wrong reading of voltage without loadActual voltage lies between 58 v to 61v (no load voltage) depending on the place as i have tested it at some location I get voltage between 230v ac and 250v acAnd the load voltage is 52vIMAGE OF PSU IS ATTACHED AND VOLTAGE IS CHECKED WITH NO LOADQuote52V with no load (all four transformer connected with each other)QuoteNo load output of every transformerTransformer 1 (12-0-12V 5amp) :ac voltage 28.4Vdc voltage 25.7VTransformer 2 (12-0-12V 5amp) :ac voltage 28.4Vdc voltage 25.7VTransformer 3 (12-0-12V 5amp) :ac voltage 28Vdc voltage 25.2VTransformer 4 (0-12V 5amp) :ac voltage 13.5Vdc voltage 12.2V(1)Transformer 1 & 2 is connected in series gaining 55.8V AC and 51.1V DC(2)Transformer 3 & 4 is connected in series gaining 41V AC and 36V DC(1) & (2) is connected in parallelQuoteYes they keep the voltageVoltage lies between 58v to 61vQuoteYes from one transformer , transformer no. 4Not so much change in temperatureBut once i have felt heating in transformer but after that never had noticed thatQuoteIMAGE OF CONTROLLERIMAGE OF THROTTLEIMAGE OF BOTH CONNECTION IS ATTACHED500w motor controllerMax current it can handle is 13AI'll update more values by testing the psu as askedThanks guys

author: Brumby
author_rank: Unknown
timestamp: October 11, 2017, 12:23:54 am
content: Transformer 4 (0-12V) is not the same as the other 3 (12-0-12V)? From your description and voltages, this would seem to be the case....QuoteThis is not what we were expecting. We were expecting the output of(1)Transformer 1 & 2and(2)Transformer 3 & 4to be the same - orvery closeto each other. With the figures you have given, they should NOT be connected in parallel.Aside from any other issues, this supply is not going to provide you with the output you want. Section (1) is going to provideallthe power until the supply is pulled below 36V. Only then will section (2) start contributing. If you want to draw 10A at 50V or so, you will be overloading section (1) since it can only deliver 5A.Transformer 4 needs to be the same - and wired the same - as the other 3.There is no need to do the "long wire resistor" test until this has been corrected.

author: Brumby
author_rank: Unknown
timestamp: October 11, 2017, 12:41:49 am
content: Had a closer look at your photo - and, yes, transformer 4 only has two wires on the secondary.Just to be clear ... the description 12-0-12 can be written as 0-12-24 or 24-12-0. They all are just as correct. Transformers 1, 2 and 3 can be described as having 0-12-24V secondaries, with only the 0V and 24V connections used.This is not compatible with the 0-12V secondary of transformer 4, for the symmetrical design you created.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 11, 2017, 02:38:18 am
content: So sir do you meanBecause of transformer 4 or the connection (2)The full supply is not given to the load .and it will power the supply only after the voltage readings goes down to 36V?

author: Brumby
author_rank: Unknown
timestamp: October 11, 2017, 06:59:33 am
content: (1) can only ever provide a maximum of 36V DC.That means that (1) cannot contribute any power until the voltage of (2) has dropped to below this value.For your circuit to work as expected, transformer 4 must have the same 24V output as the other three.

author: Raj
author_rank: Frequent Contributor
timestamp: October 11, 2017, 08:41:11 am
content: Add 2 separate current limiter and diodes to the mix assuming you want dc voltsit'll also make it start softly

author: adras
author_rank: Regular Contributor
timestamp: October 11, 2017, 09:58:24 am
content: Let's try the diagnostic somewhere else, BenKenobi already mentioned it but it seems like everyone missed it.Is your motor running at full speed when it draws just 1.5Amps? If this is the case the motor doesn't need more current. Try to slow it down while it is running, give it something to work, put a load on it, try to slow it own with your fingers, then the current will increase. And everything is working as it should.

author: Brumby
author_rank: Unknown
timestamp: October 11, 2017, 10:10:45 am
content: Before we try and get the OP to do anything else - how about we focus on getting them to sort out transformer 4?

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 11, 2017, 10:41:19 am
content: The motor is running on the full speedI have tried stopping it but the voltage levels go down to 37v and push occurs from the motor and thr voltagr level starts again from 52v snd speed starts from 0 again

author: adras
author_rank: Regular Contributor
timestamp: October 11, 2017, 11:08:42 am
content: That sounds good, how about the current draw? Does it still use only 1.5Amps when you try to stop it or does the current increase?

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 12, 2017, 05:51:33 pm
content: Sir i have done the testing of my transformer individuallyWith a load of graphite present in a pencil it did get burst out in few seconds but i got the readingsResistance on which i tested the transformer was around 7ohmReadings for transformer 1,2,3 is almost sameTransformer 1,2,3 (12-0-12v 5A)254V AC IN29.8V AC OUT26.3V DC OUT (AFTER RECTIFIER)39.9V DC OUT (AFTER 6.6mF capacitor)MAX CURRENT USING LOAD 5.9ATransformer 4 (0-12v 5A)254V AC IN14.3V AC OUT12.9V DC OUT (AFTER RECTIFIER)19.14V DC OUT (AFTER 6.6mF capacitor)MAX CURRENT USING LOAD 5.2AThrough all this reading i think the transformer is working fineBut I don't understand why the controller/motor is not able to fetch the current more than 1.5ampDo tell me which other test reading should i provideSo you all can help me resolve my issue properlyThanks

author: Brumby
author_rank: Unknown
timestamp: October 12, 2017, 10:37:22 pm
content: Thank you for those readings. They indicate the four sections of the power supply are basically functioning properly.While there is still an issue with transformer 4 not being the same as the other 3, if the maximum current draw is less than 5A, it doesn't really matter.The next question is: How thick and how long are the wires which carry the heavy current? All wires have some resistance. The thinner they are and the longer they are means higher resistance - and that will limit the current that can pass for any given voltage.Some measurements can be helpful here.The simplest is to select a reference point and connect one lead from your multimeter and leave it there for the rest of these measurements. Connect the controller and motor so they are drawing the 1.5A current. Then measure the voltageat each endof each current carrying wire. It would be good to draw a schematic and write those values at the appropriate places.When you do want to draw more than 5A though, you must either replace transformer 4 with one the same as the other 3 or get another one the same as transformer 4 and connect it in series to give thenecessary24V AC (nominal). (If you do the latter, this is where phasing is important: connecting the two secondaries in series will provide an AC voltage of either 0V or 24V, depending on whether you connect them in phase or out of phase. You only need to get 24V output to know you've got it right - and this is fed into the diode bridge.)

author: Brumby
author_rank: Unknown
timestamp: October 13, 2017, 01:51:29 pm
content: I understand we have a language barrier - and I have been trying to understand, but I am a bit lost here. Can anyone else shed some light?

author: adras
author_rank: Regular Contributor
timestamp: October 13, 2017, 02:05:21 pm
content: Quote from: VickySalunkhe on October 12, 2017, 05:51:33 pmThose two values should be the same I guess. So transformer 4 seems to "broken". So let's get rid of that transformer. Only use transformer 1 and 2 which are identical. Both together provide at least 5Amp. Use only these two transformers, and check if the motor is using more current, something like 5Amp. If that works, it shows that transformer 4 is the problem. If it still not works, the motor is running idle and doesn't need more current and you need to give it some load like a propeller.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 13, 2017, 02:13:25 pm
content: Quote from: Brumby on October 12, 2017, 10:37:22 pmI will try to change something in new responseI too felt the old response a little confusingSir i have tried two combinations of connection (main supply, psu, motor and controller)as far as the length of wire is concernedI have not measured the thickness but i have measured the resistance of wireThe wire is about 70meter long having a resistance of 3ohm which is used1st connectionThe long wire is connected before the psu (between main supply and psu) and then after the psu controller and motor is connected with a wire in between having a length of less than a 30cm2nd connectionThis is just opposite of aboveLong wire is connected after the psu (between psu and controller).In this type i felt less torque compared to (1st connection)Is this the answer you asked for ?If not plz do tell me what readings you wanted to give you.Thanks

author: jm_araujo
author_rank: Regular Contributor
timestamp: October 13, 2017, 02:41:35 pm
content: This topic is very confusing, and it seem it's approached the problem in the wrong angle.I couldn't find any reference from the OP that the motor is loaded. The current on the motor will only increase if it has a load. If if running without a load it's expected that the current is low.Also it's not very good idea to parallel 2 different power supplies, but in your case as they're not regulated the diode bridges will avoid any current flowing between them. The lower voltage one will only contribute when the parallel output voltage is lower than the voltage without load.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 13, 2017, 02:47:14 pm
content: Sir i have connected the controller and then the controller with motor onlyDo you mean i need to connect any other load to the psu with the controller+motor to draw more current?

author: jm_araujo
author_rank: Regular Contributor
timestamp: October 13, 2017, 02:57:01 pm
content: A load to the motor is something mechanical connected to it. A propeller, a water pump, a bicycle wheel. It depends on the application.A motor converts electrical power to mechanical. If it has no mechanical load, all the electricity that's consumed is for the inefficiencies (drag, winding resistance, etc).

author: IanB
author_rank: Super Contributor
timestamp: October 13, 2017, 03:13:26 pm
content: Quote from: VickySalunkhe on October 13, 2017, 02:13:25 pmThis is very wrong. Why is the wire so long? A wire conducting power should be as short as possible and should have a resistance of a fraction of an ohm.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 13, 2017, 03:30:49 pm
content: Sir my ultimate aim was to build a psu to run the motorJUST FOR TESTING PURPOSEin later stage I'll be purchasing li-ion cell pack of 13s4pBut that is costing me too much at the stage i am present so I thought to think for that in a later stageSo i thought to build a psu to give the power to motor for testing purposesI am building an E-Bike as a college projectSo the motor here is (Hub motor with wheel)Thats why i have used 70Meter of wire to test the body of bike and other stuffs

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 13, 2017, 03:32:28 pm
content: Motor used here is a hub motorUsed in a vehicle so ultimately i am giving a mechanical load on it...

author: adras
author_rank: Regular Contributor
timestamp: October 13, 2017, 03:57:34 pm
content: Can you run a test with a wire length of 30cm? I mean the wires between motor and transformer

author: Ian.M
author_rank: Super Contributor
timestamp: October 13, 2017, 04:13:06 pm
content: Due to the voltage drop from a long cable or a poorly smoothed or regulated supply the operating conditions wont be at all similar to operating your motor controller from batteries, as intended in the final application.You'd probably do better to source four used 12V Lead Acid car batteries of similar capacity, which could be in relatively poor condition as long as they can still hold a charge and don't have any dead cells so hopefully would be fairly cheap. Batteries with removable caps so you can check the acid level and top up with distilled water are preferable but they are fairly rare nowadays.Connect them in series to get a ripple free nominal 48V, that closely resembles the output of your proposed LiPO pack. The load circuit should either be fused or have an appropriately DC rated circuit breaker, with the fuse or breaker rated to interrupt a minimum of 60V DC, as such a set of batteries even in poor condition could put a very large current through a short, and there is a risk of explosion if you short a recently charged Lead Acid battery and there is a cracked internal connection that cant carry the full short circuit current, or if the electrolyte boils due to Joule heating.Then you need to charge them - you could do so one at a time from a CC/CV bench supply with a series Schottky diode to prevent reverse current if input power is lost, or you could build a charger for them - probably the easiest would be 48V RMS from your transformers, a bridge rectifier and a series ballast resistor to limit the maximum charging current + a relay to disconnect its input power when fully charged. Due to the unknown history of the batteries they are likely to have dissimilar actual capacities so will require balancing - for that you can simply add a shunt regulator across each one set to about 14V, that can pass the full charger output current. Detect when all four shunt regulators are passing significant current, and start a timer to terminate the charge using the relay and disconnect the shunt regulators. Charging should ONLY be performed with adequate ventilation. Alternatively if you can obtain four small smart float chargers for Lead Acid batteries, with two wire mains leads (no ground), simply connect one across each 12V battery.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 13, 2017, 07:03:15 pm
content: Sorry but the readings which i posted last time out of thatOne of the transformer reading was wrongNew and correct readings are as such259V AC INTransformer 1 (12-0-12v 5A)29.8V AC OUT26.3V DC OUT (AFTER RECTIFIER)39.9V DC OUT (AFTER 6.6mF capacitor)MAX CURRENT USING LOAD 5.2ATransformer 2 (12-0-12v 5A)14.8V AC OUT13.01V DC OUT (AFTER RECTIFIER)20V DC OUT (AFTER 6.6mF capacitor)MAX CURRENT USING LOAD 4.3ATransformer 3 (12-0-12v 5A)29.9V AC OUT26.6V DC OUT (AFTER RECTIFIER)40.8V DC OUT (AFTER 6.6mF capacitor)MAX CURRENT USING LOAD 5.2ATransformer 4 (0-12v 5A)14.3V AC OUT12.7V DC OUT (AFTER RECTIFIER)19.8V DC OUT (AFTER 6.6mF capacitor)MAX CURRENT USING LOAD 4.3AFor a complete psu giving out 59V DC (without load)(1)Transformer 1&2 are in series(2)Transformer 3&4 are in series(1) & (2) are in parallel

author: adras
author_rank: Regular Contributor
timestamp: October 13, 2017, 07:22:13 pm
content: Ok, to simplify things, please run the following test.Use Transformer 1 and 3 only to power the motor. Use 30cm/11" cables between transformer and motor.@All, if the wires have a too small diameter they should get hot/burn through, right? I doubt that too slim wires would just reduce the current flow in this "high" current scenario.

author: Brumby
author_rank: Unknown
timestamp: October 14, 2017, 12:01:29 am
content: Quote from: adras on October 13, 2017, 07:22:13 pmIt depends ... but significant voltage drop over short lengths would be expected to heat things up noticeably.Quote from: VickySalunkhe on October 13, 2017, 07:03:15 pmFrom this it seems you have only wired half of the secondary (the photo seems to support that). In this case, the total voltage of (1) and (2) are close, so all 4 transformers of the supply can be used as you originally intended.From the current tests, you say "MAX CURRENT USING LOAD". But what is the load? This is very important for the readings to be meaningful.Aside from the precise current capability, I am feeling less concerned about the supply at this point - but, as has been mentioned earlier, there are some questions surrounding the operation of the controller and the specific loading of the motor...

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 14, 2017, 02:49:22 am
content: A load of graphite present in a pencil is used as a load, it did get burst out in few seconds but i got the readingsResistance on which i tested the transformer was around 7ohm

author: Brumby
author_rank: Unknown
timestamp: October 14, 2017, 12:16:43 pm
content: So - just to confirm - your meter was in series with the 7 ohm graphite pencil - and this combination was then connected across the power supply being tested? Thus the total load will be 7 ohms plus the resistance of the internal 10A shunt.This cannot be right. The maths simply does not work for transformer 2 and transformer 4 - even just using the 7 ohms as the total load.Using Ohm's Law: V=IR rewritten as I=V/RThus: 20V DC / 7 ohms = 2.86Aand... 19.8V DC / 7 ohms = 2.8Aas such, these are maximum possible values and neither of these agree with the current readings given.Something is wrong.Can you pleaseshowusexactlyhow everything is connected when doing these current measurements.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 14, 2017, 12:26:37 pm
content: As soon as i turn on the psu the graphite used heat up and smoke used to come and the current rating increases drasticallyI have given you the highest rating of current before the graphite has torn out leaving the circuit open.(ALL THIS HAPPEN WITHIN COUPLE OF SECOND)So I don't know what is the actual resistance as the graphite heats up i think resistance will come down thus giving out more currentBut the main task which was to test whether transformer can give out 5A or not was completed so i gave out the readings which i have got

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 14, 2017, 12:44:01 pm
content: Final readings of motor connected to vehicle body and tested it by using a load of 70kg on the vehicle70 meter long wire between main supply and psu15 cm long wire between psu and controllerWidth of wire 1mmTransformer 1 (12-0-12v 5A) Transformer 2 (12-0-12v 5A)RATINGS WITHOUT LOAD30V AC OUT 14.8V AC OUT26.7V DC OUT (AFTER RECTIFIER) 13.01V DC OUT (AFTER RECTIFIER)40.7V DC OUT (AFTER 6.6mF capacitor) 20V DC OUT (AFTER 6.6mF capacitor)RATINGS WITH CONTROLLER,MOTOR, THROTTLE (NO MECHANICAL INPUT ISGIVEN TO THROTTLE)36V DV 0.06A 17V DC 0.11ATransformer 1&2 in seriesWithout load 58.6VWith some input to throttle and controller, motor is connected52.5V 0.05A44.1V 0.55A38V 1.11A35V 1.45AAfter 35V controller stops to give any power to motor and starts from 52V againTransformer 3 (12-0-12v 5A) Transformer 4 (0-12v 5A)RATINGS WITHOUT LOAD29.9V AC OUT 14.5V AC OUT26.6V DC OUT (AFTER RECTIFIER) 12.7V DC OUT (AFTER RECTIFIER)40.8V DC OUT (AFTER 6.6mF capacitor) 19.8V DC OUT (AFTER 6.6mF capacitor)RATINGS WITH CONTROLLER,MOTOR, THROTTLE (NO MECHANICAL INPUT IS GIVEN TO THROTTLE)36.1V DV 0.06A 16.8V DC 0.11ATransformer 3&4 in seriesWithout load 58.5VWith some input to throttle and controller, motor is connected52.5V 0.05A44.4V 0.55A38.4V 1.15A34V 1.5AAfter 34V-37V controller stops to give any power to motor and starts from 52V again1+2 connected parallel with 3+453V 0.05A47.9V 0.57A43.9V 1.2A37.1V 2.62A42.2V 1.75A49.6V 0.55A36V 2.85AAs soon as the voltage drops down between 34V - 37V motor starts from starting i.e, 52VCurrent reached to 2.6A max with a load of 70Kg on vehicleWith all 4 transformer connectionWith 2 transformer connected seriallyMax 1.36A current is attainedBut theoretically i can get 7A of currentBut practically current i am gettung is 2.6AThat's the problemPlz help me to resolve the issue if anyThanks

author: StillTrying
author_rank: Super Contributor
timestamp: October 14, 2017, 02:27:47 pm
content: "After 35V controller stops to give any power to motor and starts from 52V again"As the motor controller is expecting to be powered by lipo batteries it's probably switching off to protect the lipo batteries from over discharging.I don't think you'll be able to get the current much higher than you already have from a transformer and bridge rectifier.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 14, 2017, 02:37:44 pm
content: Quote from: StillTrying on October 14, 2017, 02:27:47 pmBut why?The configuration of transformer i purchased should deliver (5A) for what they are made for right?Or is it likeIn a center tap transformerIf 1,3 wire is joined with a bridge rectifier we get half the current for what the transformer was made for.

author: Ian.M
author_rank: Super Contributor
timestamp: October 14, 2017, 03:10:09 pm
content: No. If from an honest manufacturer, a transformer fed from a supply of its nominal primary voltage can supply its full rated RMS secondary current into a resistive load, without overheating if cooled as specified, and without the secondary voltage dropping below its rated value, *HOWEVER* a bridge rectifier followed by a capacitor is *NOT* a resistive load, even if there is a resistive DC load after the bridge rectifier. You have to apply the derating factor of 0.62 for this configuration, as shown in the PDF I linked back in reply#44:Quote from: Ian.M on October 09, 2017, 05:03:27 pmThat derating factor can be confirmed by circuit analysis, either manually or by SPICE simulation.Therefore your5A RMStransformer secondaries are only good for fractionally over3A DC, when used with a bridge rectifier and reservoir capacitor.

author: IanB
author_rank: Super Contributor
timestamp: October 14, 2017, 03:17:30 pm
content: I disagree. There is no derating factor for this application. The derating factor protects against overheating, it does not limit the maximum current the transformer can produce. For short periods of maximum load all that will happen is that the transformer might get a bit warm.I think instead we have to look to the 70 m long wire. This was said to have a resistance of 3 ohms in a previous post. Is this resistance for just one leg, or for out and back combined?5 A through 3 ohms will drop 15 V, and 5 A through 6 ohms will drop 30 V. This will drastically limit the voltage the motor sees when you open the the throttle and put a load on it.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 14, 2017, 03:19:16 pm
content: Quote from: Ian.M on October 14, 2017, 03:10:09 pmThats what i am worried about sirAs per your sayingI should get 3A from one transformerBut i am getting 1.3A from itWhich is the problem

author: IanB
author_rank: Super Contributor
timestamp: October 14, 2017, 03:24:22 pm
content: Get your 70 m wire, join the two conductors together at one end, then measure the resistance between the two conductors at the other end. What is the total round trip resistance of the wire, out and back?

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 14, 2017, 03:24:51 pm
content: Sir today i have tried to replace the 70meter wire with 30cm wireBut there was not any major difference between the readings which i have posted today only...

author: Ian.M
author_rank: Super Contributor
timestamp: October 14, 2017, 03:33:35 pm
content: The derating factor is applicable if you dont want to burn up your transformer in continuous operation. Transformers are not fussy pieces of silicon, they are Iron, Copper and usually plastic insulation, and they tolerate brief overloads well as long as the deep winding temperature stays under the maximum temperature rating of the wire insulation. Better manufacturers will even specify permissible overload factors and duty cycles.Quote from: VickySalunkhe on October 14, 2017, 03:19:16 pmYou can getUP TO 3Acontinuously without burning out your transformer, and probably 6A for a few seconds, but that doesn't mean your motor controller *will* draw 3A (or 6A).Quote from: IanB on October 14, 2017, 03:17:30 pmI agree that much of the problem is the wire resistance. 1mm dia wire is near enough 18AWG, which if made from good quality electrical grade copper should be about 21 milliohms per meter. For 140 meters (70 m there and back), that comes to almost exactly 3 ohms.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 14, 2017, 03:33:51 pm
content: Quote from: IanB on October 14, 2017, 03:24:22 pm5 Ohm

author: Ian.M
author_rank: Super Contributor
timestamp: October 14, 2017, 03:42:19 pm
content: Can you confirm the 1mm wire diameter? Also, what's its strand count and individual strand diameter? Stranded wire can have up to 1/3 more resistance than solid wire of the same diameter, due to its packing fraction (i.e. the voids between close packed circular strands), but that would only account for 4 Ohms of resistance. If you are measuring 5 Ohms and its not a measurement error, and the diameter is actually 1mm, it implies the copper is crappy, with a bulk resistivity 25% higher than pure electrical grade copper.

author: WaveyDipole
author_rank: Frequent Contributor
timestamp: October 15, 2017, 05:12:36 pm
content: I had a look at the photo and am concerned as to how TX2 is wired. It is difficult to tell on the photo but I fear that there may perhaps be some confusion because instead of red-blk-red as per TX1 and TX3, TX2 has the opposite, i.e. blk-red-blk. It is difficult to tell which wire goes to the right side of the terminal block, but the direction of loops in the black wires seem to suggest that one of the black wires is wired into the left side of the connector block but has had a length of insulation stripped back at its mid point (just left of exit point of the red wire) and then the end of the topmost black wire loops back and its end is wrapped around this same point. The red wire then seems to go to the right terminal of the connector block. I hope that is NOT what is going on here and perhaps this is the bare end of one black dangling loose above the other and obscuring the insulation otherwise that TX would be getting really hot! The red wire should be the center tap and ought to be left disconnected. The two black wires should be connected to the connector block, but apologies if I have mis-interpreted the picture.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 16, 2017, 04:30:23 pm
content: Quote from: Ian.M on October 14, 2017, 03:42:19 pmWire diameter 0.83mmStrand count 10Strand diameter 0.3mm

author: Ian.M
author_rank: Super Contributor
timestamp: October 16, 2017, 04:52:07 pm
content: There's something wrong there as the sum of the strand cross section areas (CSA) comes to more than the overall CSA calculated from the overall diameter.70m of a solid pure copper wire of 0.83mm diameter would be 2.174 ohms, so with the loss due to the voids between strands 5 ohms is in the right ballpark for 70m x 2 wires.That wire is ludicrously thin for the purpose - 2.5 mm2mains flex would be a far better choice, and I would strongly advise at least 2000uF per Amp bulk decouping at the motor controller as I bet it draws high current pulses.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 16, 2017, 04:56:12 pm
content: Sir can you plzTell me how you calculated all this calculationAnd what do they mean?And what minimum diameter wire shall i use for this purposeThanks

author: Ian.M
author_rank: Super Contributor
timestamp: October 16, 2017, 05:22:05 pm
content: resistance = resistivity × length / areaarea=Pi*(d/2)2Wikipedia says: Pure Copper electrical resistivity = 16.78 nanoohm·m (at 20 °C)The rest is just simple maths.In practice it will be worse than the calculation gives because the copper wont be 100% pure and the overall diameter makes no allowance for the voids between strands.The minimum wire diameter is determined by how much voltage drop your application can tolerate. Calculate the maximum wire resistance you can tolerate then look through a cable manufacturer's catalog for a cable with a low enough resistance per meter to be under that after multiplying by the total wire length there and back.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 16, 2017, 05:39:50 pm
content: Quote from: Ian.M on October 16, 2017, 05:22:05 pmSryBut I didn't get any of this sir.How would i know how much minimum voltage drop my application can tolerate or what does it mean actually?How would i know what is the max wire resistance i can tolerate?How would i know what diameter wire can support 5A current and have minimum resistance.....

author: Damianos
author_rank: Frequent Contributor
timestamp: October 16, 2017, 08:41:57 pm
content: Most of the presented measurements seem a little or a lot strange!For example, the voltage with a50mA loadissix voltslower than what measured without load!It is not clear where the measurements are done. Are these on the controller or at the output of the circuit?You forgot to say what are thetypes of the rectifiers. Have you found a datasheet of them?Are the transformers of any "special" type? What is showed on their labels?Are all the capacitors of the same type/model? What is their workingvoltage rating?How is the circuit constructed, under the cartons? Is possible to show a photo?Are connected the components with very thin wires? There are mentioned measurements with and without the capacitors, how are they connected and it is so easy to disconnect and reconnect them?... ...One more test that you can do, is to try to measure the ripple voltage of the power supply. Set your meter to AC voltage, measure at the output without and with a little load, on each of the four and the entire combination of them. [with capacitors connected]If an instrument with peak detect is available, the above will be more informative.

author: Brumby
author_rank: Unknown
timestamp: October 17, 2017, 12:49:16 am
content: Quote from: Ian.M on October 16, 2017, 05:22:05 pmWhile straightforward to many of us, I was concerned that this was too much of an ask from our OP. So, rather than set them on a difficult task, I had a look at the cable they have at hand.From the photo, it would seem the OP is using a mains rated cable - thick white sheath with red and black insulated wires within - but that it would be at the lower end of current carrying capacity. My guess is it would be for lighting circuits. Also, at 5 ohm for 140m it works out as 0.036 ohms per metre. With 10A current that is about 0.7V drop per metre of twin cable. So long as the cabling throughout the supply is ofat leastthis gauge and the total length from the transformers to the load is less than, say, 2m I can't see a 1.5V drop being a problem. Going heavier gauge is never a bad idea - but this should work for testing.Questions to OP:1. Is all the wiring connecting all your components of this gauge or thicker?2. What is the total length of wiring from the transformer to the load? (Just answer for a single wire - and we will double it for any maths.)Quote from: Damianos on October 16, 2017, 08:41:57 pmThis is something I have wondered as well. In the photo, I don't see any soldered joints, just the terminal blocks used to connect the transformers. How are the connections we can't see being made? If you are simply twisting wires together, then there is going to be a lot of potentially poor connections, especially for pulling currents of 5A and more. Heavy current connections need to have very good contact or you will lose a lot of power. The terminal blocks are a good move, but what else are we not seeing...?Request to OP:3. Can you please show us a photograph of the hidden wiring?Quote from: Damianos on October 16, 2017, 08:41:57 pmThis has been a problem from the very outset.Whereyou measure a voltage is important and for higher current situations can be absolutely critical for understanding what is actually going on. There is also the issue that we are not seeing the complete setup, so there may be some hints or obvious errors that are invisible to us.Request to OP:4. Can you please provide a schematic of theentirecircuit - from the supply, through the controller to the load? (Do not try to look inside the controller - just show the connections to it.)QuoteThis would be an interesting - and useful - test.With no load, we would expect this AC voltage to be pretty small and, essentially, insignificant. When this DOES become interesting is when you put a load on it. I would be interested to see what it was like at around 1A load current. The actual current isn't hugely important - but if you can measure it accurately, that will help in doing some math. Oh, and don't forget to do the DC voltage measurement as well.Request to OP:5. Can you test the supply as suggested showing:a) DC volts, AC volts - with no load and..b) DC volts, AC volts, DC amps - for a load current between 0.5a and, say, 3A

author: Connoiseur
author_rank: Regular Contributor
timestamp: October 17, 2017, 04:18:27 am
content: Suggestion to OP:You can make your own crude resistive load from nichrome wire wound on a suitable former like ceramic tile or a mud brick, although personally, I prefer brick as it does not crack on heating. Nichrome wire is easily available in most of the electrical shops as heater wire rated 1500W at 230V. Alternatively you can buy a rheostat of suitable rating.Quote from: Ian.M on October 16, 2017, 05:22:05 pmI beg to differ. Commercial copper wires available today have more than 100% of IACS conductivity. Also, the area mentioned on the wire (at least the ones IS 694:2010 certified) is the actual area of all the strands combined, so the "packing void factor" is ruled out. But yeah, the temperature may not be 25 deg. C at OP's location, so the resistance will be a bit higher.

author: Ian.M
author_rank: Super Contributor
timestamp: October 17, 2017, 05:10:01 am
content: Quote from: Connoiseur on October 17, 2017, 04:18:27 amIACS commercial grade annealed copper: 17.241 nanoohm·m,Wikipedia's figure for Pure Copper: 16.78 nanoohm·m, both at 20 °C.Modern commercial grade copper is between the two, due to process improvements since the IACS standard was set in 1913.I would no longer bet on cheap wire being made with pure commercial copper - if its made of low purity recycled copper, contaminated with brass, solder and other metals, its resistivity can be significantly higher, before the impurity level rises to the point where the decreased ductility adversely affects the wire drawing process.Also the O.P. quoted the wire diameter as 0.83mm (presumably measured), which I then calculated the area from, as the strand diameter and count was inconsistent and did not give the CSA. Therefore I stand by what I said.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 17, 2017, 06:57:07 pm
content: First i have done some changes in the circuit with wireswhich resulted in increase of output current by 1 amp i.e, max i can get is 3.5A from my psu. But still its half way down considering the fact my output current will be 62% of rated current value.and an update in readings of previous wire used length of wire was 35 meter sorry, but because of some confusion i told you 70 meter earlierWire used between psu and controllerand between capacitor, rectifier.....TOTAL length of wire used back and forth 1.9 meterDiameter of wire 2.5 mmNo. of strands 36Strand diameter 0.33 mmsame wire was used between main supply and psu for carrying 252 V ACLength of that wire 37 Meter [of one wire double it for two wires]resistance of above wire (two wires connected) 1.3 ohmQuote from: Brumby on October 17, 2017, 12:49:16 amPreviously wire was thin of 0.83mm but now as i have said earlier because of changes doneThicker wire .Quote from: Brumby on October 17, 2017, 12:49:16 amTOTAL LENGTH both side 1.9 Meter ( don't double this value)Quote from: Brumby on October 17, 2017, 12:49:16 amIMAGES ATTACHED OF CONNECTION AND HOW MULTIMETER IS USED AND WHERE.Quote from: Brumby on October 17, 2017, 12:49:16 amIMAGE OF SCHEMATIC ATTACHEDQuote from: Damianos on October 16, 2017, 08:41:57 pmQuote from: Brumby on October 17, 2017, 12:49:16 amTransformer / CircuitDC VOLTAGEAC VOLTAGEFull Circuit58.6V128.6V1 & 2 (IN SERIES)58.2V127.6V3 & 4 (IN SERIES)58V127.6Vtransformer 139.2V85.7Vtransformer 219.2V41.8Vtransformer 339.4V86Vtransformer 418.93V40.8VQuote from: Brumby on October 17, 2017, 12:49:16 amFull Circuit1 & 2 (IN SERIES)3 & 4 (IN SERIES)56.8VDC 125VAC 0.05 A56.1VDC 123.2VAC 0.05 A55.8VDC 122.9VAC 0.05 A46.5VDC 99VAC 1.5 A49.1VDC 108.2VAC 0.5 A49.8VDC 109.3VAC 0.5 A43.5VDC 95VAC 2 A43.5VDC 96.2VAC 1 A44.6VDC 98.1VAC 1 A37VDC 81VAC 3.4 A(MAX)42VDC 92VAC 1.16 A(MAX)43VDC 94.3VAC 1.17 A(MAX)Readings for full circuit are not accurate as i was not able to take readings on specific current value as i have taken for half circuitI have some doubts nowdespite of changing the wire which can handle 10ampspsu is not able to supply even 7AI have strong doubt about the center tap transformeri think i have read somewhereby connecting wire 1 and 3 we get half the rated current is that true ?All the connections are rigid now so there will be no leakage current think so...TWO MORE REPLIES ARE ADDED BECAUSE I WAS NOT ABLE TO UPLOAD ALL THE IMAGES BECAUSE OF POST RESTRICTIONS

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 17, 2017, 06:59:18 pm
content: Two more imagesneed to upload two morewas not able to do so because of post restrictionsorry for inconvenience

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 17, 2017, 07:06:11 pm
content: Last two imagesQuery still remains the sameDespite of bulding psu for giving output of 10A or 7A( because of losses)I am still getting 3.5A max which is still half than what i am expecting.

author: Zero999
author_rank: Super Contributor
timestamp: October 17, 2017, 08:08:54 pm
content: My bet is poor wiring. The solder joints are not wetted properly and twisting wires together like that doesn't ensure a good electrical connection!

author: Damianos
author_rank: Frequent Contributor
timestamp: October 17, 2017, 09:52:05 pm
content: Bad wiring, that's for sure.As mentioned all the solder joints need "repair", also the twisted wires need soldering, especially the connections of the rectifiers.By the way, are the mains' connections well made and safe? It looks like there are bare feet there!Some more notes:- if the rectifiers are all the same, they are 35A/1000V, that is good enough. But this seems that is the only one good thing here!- if the capacitors are all the same, some of them are abused! On one of them it is written 50V![Edit: it seems that I have confused the numbers! These capacitors have enough voltage margin.]- the transformers have all the same dimensions, but two of them are 60VA and the others are 120VA, this is not possible!The refereed AC values are not related with something else, at least they don't seem as ripple voltages. Where are they measured? Maybe the instrument has a strange behavior when it has AC over DC at its input(?).

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 18, 2017, 03:35:58 am
content: Quote from: Damianos on October 17, 2017, 09:52:05 pmI have made the connections to the transformer as such to getAround 38V from two transformersAround 14V from remaining two transformersI have total 4 transformer3 of them are center tapped transformer 12-0-12V 5amp4th transformer is 0-12V 5ampOut of 3 center tapped transformer one transformer wiring had been done (wire 1,2 connected) so as to get 14V to match up with 4th transformerAnd I tried to solder the wire with the rectifier but the solder wire is not getting stuck woth rectifier metal points.

author: Ian.M
author_rank: Super Contributor
timestamp: October 18, 2017, 04:14:51 am
content: What soldering iron are you using?If the iron isn't up to the job, you'd be better off connecting the rectifiers with female spade crimp terminals, and joining the wires with screw terminals - either with ring crimp terminals secured by the terminal screw, no more that three ring terminals per screw, or by screw 'choc' block terminals with no more than two wires per side per hole.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 18, 2017, 04:21:47 am
content: Will replacing the copper wire used for connectionsWith metal wire solve the issue of bad wiring?Single Metal wire of thick width of about 2mm?Will that work?

author: Brumby
author_rank: Unknown
timestamp: October 18, 2017, 04:55:07 am
content: Quote from: VickySalunkhe on October 18, 2017, 04:21:47 amDon't bother with that. The copper wire used here should be more than good enough to solve your major problems. Whether you need to go any thicker is a question for later.When the phrase "bad wiring" is used here, we are talking about how well the terminations have been done. In short - your connections are poor.If we were to criticise the actual wire you have used, we would have said things like "poor quality wire", "inadequate" or things like that.

author: Brumby
author_rank: Unknown
timestamp: October 18, 2017, 05:00:55 am
content: Quote from: VickySalunkhe on October 17, 2017, 06:57:07 pmNo.Only the voltage of a centre-tapped secondary is different, depending on which connections you use. Thecurrent ratingwill be thesamefor any combination.

author: Brumby
author_rank: Unknown
timestamp: October 18, 2017, 05:05:46 am
content: Quote from: VickySalunkhe on October 17, 2017, 06:57:07 pmThose AC volts readings are bizarre.

author: Damianos
author_rank: Frequent Contributor
timestamp: October 18, 2017, 05:08:56 am
content: Quote from: VickySalunkhe on October 18, 2017, 03:35:58 amI was wrong! The voltage rating of the capacitors looks good enough.The power of the transformers that you have are 12V*5A=60VA and 24V*5A=120VA, but they have the same dimensions.

author: Brumby
author_rank: Unknown
timestamp: October 18, 2017, 05:57:44 am
content: Quote from: Damianos on October 18, 2017, 05:08:56 amMy guess is that the manufacturer got a great deal on E-I cores and made up a couple of variants with different secondaries. (There's less copper in the 60VA versions.)

author: Brumby
author_rank: Unknown
timestamp: October 18, 2017, 06:06:12 am
content: Quote from: Brumby on October 18, 2017, 05:05:46 amNot only are those AC voltage readings way too high, but they should beincreasingwith greater load, not decreasing.These AC voltage readings should have been made across the capacitors - exactly the same points as the DC voltages. Is that where they were made?

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 18, 2017, 06:10:50 am
content: Quote from: Brumby on October 18, 2017, 06:06:12 amYES

author: Brumby
author_rank: Unknown
timestamp: October 18, 2017, 06:15:19 am
content: This may sound like a strange request - but repeat just one of those AC voltage measurements and then swap the meter leads and measure it again...Does the meter give you the same reading?

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 18, 2017, 06:55:43 am
content: Quote from: Brumby on October 18, 2017, 06:15:19 amNOWhile testing the AC voltages swapping the meter leads gave output of 0V for all combinations

author: Brumby
author_rank: Unknown
timestamp: October 18, 2017, 08:17:55 am
content: Now I am officially confused.How come we have gone from AC measurements ranging from 40V to 126V - to 0V?

author: Damianos
author_rank: Frequent Contributor
timestamp: October 18, 2017, 08:21:55 am
content: Quote from: Brumby on October 18, 2017, 05:57:44 amMaybe it is more cost effective for them to use the same cores and bobbins (?).

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 18, 2017, 08:24:54 am
content: SirI am testing a dc voltage by setting the dial on acSo it must give high voltage on one side and 0 voltage on other side rightAm i right?OrYou are asking something different which i have not got yet

author: Damianos
author_rank: Frequent Contributor
timestamp: October 18, 2017, 08:39:50 am
content: Obviously the instrument has not an AC coupling, so it shows strange results. It is seemed that it uses half wave rectification...If there is a capacitor available, of more than 1 micro Farad, putting it in series with the instrument will give an indication of the ripple. This has to be zero without load and increasing with the output current.

author: Brumby
author_rank: Unknown
timestamp: October 18, 2017, 10:09:36 am
content: Quote from: Damianos on October 18, 2017, 08:39:50 amThat isnotobvious - but it is a possibility.Whatisobvious is that we have some measurement issues.QuoteThis is an idea - but the capacitor must be allowed to charge up to match the DC offset.

author: Damianos
author_rank: Frequent Contributor
timestamp: October 18, 2017, 04:44:44 pm
content: Quote from: Brumby on October 18, 2017, 10:09:36 amHow do you explain this:Quote from: VickySalunkhe on October 18, 2017, 06:55:43 am... if it is AC coupled?QuoteWhat prohibits the capacitor to charge up?

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 18, 2017, 04:54:29 pm
content: QuoteSir as i am using full wave rectifier to convert ac to dcOne side will be double of the orginal amplitudeSo acc. To that other side will have 0 VSo that's what i am gettingWhile i am getting some reading when i swap the meter leads of multimeter to the connectionIt shows 0V and it should right?

author: Damianos
author_rank: Frequent Contributor
timestamp: October 18, 2017, 07:16:21 pm
content: I can not understand the meaning of your description. Where do you mean there is a double voltage?What are you measuring? Can you show this on a diagram?

author: Brumby
author_rank: Unknown
timestamp: October 18, 2017, 11:36:41 pm
content: Quote from: Damianos on October 18, 2017, 04:44:44 pmThe OP isn't measuring what youthinkthey are measuring. This is borne out by this post of yours...Quote from: Damianos on October 18, 2017, 07:16:21 pm... and this is something that I have been wanting to see for some time. I have an answer in the pipeline...QuoteThe impedance of the multimeter and time. With a fully discharged 1uF cap and a 10M DMM input impedance, it will take around a minute for it to charge within 10% of the supply voltage and close to 2 minutes to get within 1%. If there are any DC offset issues with the meter, then the DC component of the measurement setup needs to be zero. There is a way to speed this up, though. Simply charge the capacitor directly off the supply first. One more consideration - that the capacitor have low leakage, otherwise the DC current flow could cause problems.

author: Gregg
author_rank: Super Contributor
timestamp: October 19, 2017, 02:45:07 am
content: Sometimes it is better to just start over. By that I mean take it all apart and put it back together one part at a timemaking sure all connections are really good.Test each part before connecting it to another and then test in circuit at each logical step of the assembly process. Labeling the wires may help to test further as you assemble each power supply.1. Take one transformer and test the input AC voltage and output voltage no load. Make sure the output is what you expect and for the dual winding ones this will ensure they two aren’t cancelling each other.2. If possible put a load on the transformer output and measure the voltage again both in and out. Write down the results3. Next add a bridge rectifier and test again both open circuit and with a load for AC volts on the input of the rectifier and DC volts on the output terminals4. I would leave the capacitors out until near the final testing5. After you have assembled the two higher voltage systems, try paralleling them and take some more readings. If they are what you expect try them on the motor control and see what happens.6. Continue piece by piece in an orderly fashion until it either works or you see something that isn’t right.7. Post the results.This is how you learn, by making mistakes and figuring them out; lessons you won’t forget.( It is quite rare to officially confuse Brumby )

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 19, 2017, 03:41:14 am
content: SirReadings onPost no. 98 was taken by rebuilding the circuit part by part as you suggestedBy which i got an increase of output current by 1ampBut still it wasn't upto expectationI have provided you all the true readingsI don't knowWhether i have been wrong with the readings you all asked for or not.I think brumby got confused as soon as i posted readings of ac voltage to find out the rippleCan any one plz tell me little bit clearly what was he actually asking forAnd from where should i measure it and with which parts connected to thr transformerI have taken all those reading while all parts (cap, rectifier,motor) were connectedAnd took the readings from the points where i have taken the readings of dc voltageFor ac i just switched the dial of multimeter to ac voltageIs that wrong or something is?

author: Brumby
author_rank: Unknown
timestamp: October 19, 2017, 07:50:10 am
content: I am drawing up something that will make the measurement process clear.... I have some pressing priorities, so please be patient.

author: Gregg
author_rank: Super Contributor
timestamp: October 19, 2017, 07:54:34 am
content: I guess I thought I could slip in a lesson in basic physics for you to see hands on what happens when trying to parallel rudimentary DC power supplies. Also I was curious as to how much the mains voltage dropped when this system was attempting to power your full load and to see if there was significant voltage drop across any of the twisted wire connections or bridge rectifiers with a bad diode.Basically the power supply with the greatest potential (voltage) will try to power the entire load. Other power supplies at lower potential won’t contribute anything unless the highest potential one sags to the next supply’s potential and even then the load won’t be shared equally.This is very similar to charging lithium batteries and need for balancing every cell (only in reverse).You could make actively controlled rectifiers using things like SCRs and balancing control circuitry to effectively force each power supply to the same potential with current control for dissimilar transformer output capacities but that is way beyond the scope of this thread and hardly worth the time and effort considering a single transformer of suitable capacity would be much cheaper in your case.The telco industry uses nominal 48 volts DC supplied by huge batteries and multiple chargers (called rectifiers in telco language) that all parallel and share the load. If the share wiring between the chargers gets compromised then they fail to share but they have the safety of current limiting where some rectifiers go to full load and others go to zero load. They also have at least one more rectifier on line at any given time than absolutely necessary (N+1 redundancy)In your system the transformer with the highest potential provides current until magnetic saturation and there is no current limiting or voltage regulation to save it.

author: Brumby
author_rank: Unknown
timestamp: October 19, 2017, 04:54:32 pm
content: OK... Reference schematic....How I envisage measurement requests...VAB= Voltage between pointsAandBVJK= Voltage between pointsJandKIL= Current flowing past pointLIJ1= Current from Section 1 flowing past pointJIJ2= Current from Section 2 flowing past pointJIJ= IJ1+ IJ2(Kirchhoff's current law)VKQ= Voltage drop from pointK(supply) to pointQ(controller).. and how they would be reported.I hope I have it right. All equipotential points within the supply have been considered to be exactly that. Only for the longer wires has there been an allowance to measure voltage drops.Hopefully this will allow for unambiguous measurement reference points - which I hope will be a start in clearing some confusion. We still need to be conscious of clear communication with regards to specifying AC and DC ... and anything else we need to be aware of - such as the specific conditions (eg load) under which these measurements are made.Apologies if I don't participate as significantly over the next several days... some other priorities I cannot ignore.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 19, 2017, 07:45:21 pm
content: Hello sirFirst of all thankyou very much for helping me outJust wanted to tell you that i have told you all the readings from the points you have mentioned aboveExpect for the current from point LI don't understand there one thingI'm connecting a +ve and -ve wire for a series connectionHow can i measure current from there , can i ?And how can i measure thisVKQ = Voltage drop from point K (supply) to point Q (controller)I am sorry but it got me little confusing.Thanks

author: Brumby
author_rank: Unknown
timestamp: October 20, 2017, 12:23:43 am
content: Quote from: VickySalunkhe on October 19, 2017, 07:45:21 pmI expect you have ... but there is the question: Which ones are theyexactly? This may sound strange, but what you think is clear and what others think is clear - may not be the same thing. Most of the time, it would be straightforward - but as we get deeper into this, being exact is important.QuoteUnless you have a clamp meter that can do DC current (which most beginners won't have) you measure current the old fashioned way - break the circuit at that point an insert an ammeter.QuoteJust use the reference as a definition - such as this:VKQ- Meter on Volts (probably DC)- Red lead of meter on point K- Black lead of meter on point QThat is how.It may seem strange to measure the voltage from one end of a piece of wire to the other - but it is not. It is important to make sure that when you put your meter lead on point K, that it is as close to the power supply negative rail as possible. Likewise, point Q should be as close to the controller as possible.The measurement, however, will be dependent on the current flowing. If there is no current flowing, the answer will be zero, but if there is a heavy current flowing - there will be a measurable voltage drop. In this example, expect the answer to be negative, since point K is on the negative supply rail and will be below the potential of every other point of the DC circuit.If your connections are good and the wire gauge is heavy enough - then these "end-to-end" measurements on the wires should be very low under load. You are getting large voltage drops which shouldn't be happening according to what we are understanding - so there must be some part of the circuit that is NOT behaving as expected.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 21, 2017, 07:03:38 am
content: Quote from: Brumby on October 19, 2017, 04:54:32 pmVAB= 30V ACVJK= 54V DCAll current values are max value i got by motor running at full speedIL= 1.42AIJ1= 1.42AIJ2= 1.42AIJ= IJ1+ IJ2(Kirchhoff's current law)IJ= 2.84AVKQ= 0VNo change of voltage occurred when motor was at 0 speed and full speedAnd sir i have replaced the LONG WIREso don't consider the voltage drop for thatThe total wire distance back and forth between transformers and controller is 1.9meter

author: Brumby
author_rank: Unknown
timestamp: October 22, 2017, 12:59:45 am
content: Quote from: VickySalunkhe on October 21, 2017, 07:03:38 amOK ... Now we have some clear measurement points. If we all use this nomenclature, then there will be much less confusion as to what is being measured.However, from the above figures, someone could ask ... So what is the problem? VJKlooks good and the current measurements seem reasonable.From these figures, VJKis always 54V ... which, from previous discussion, does not seem to be the case. This means you need to specify theconditionsunder which any given measurement is taken.For example:VJK= 54V DC @ IJ= 2.84A-or-VJK= 54V DC @ IJ= 0A-or-VJK= 54V DC @ some other conditionKnowing what the circumstances are for any given measurement are just as important as the measurement itself. Power supply and high current circuitry are classic examples - so are electric motors.Without even thinking, I can name 4 states for an electric motor that willcompletely changethe load characteristics...- disconnected- unloaded (free spinning - just the motor shaft with nothing connected to it)- typical load (doing the work it would need to do to move a scooter with someone on it)- stalled (shaft prevented from rotating)These are arranged in ascending order of the electric load on the power supply - and they willdrasticallyaffect the current demands from the power supply. The mechanical load condition of the motor is, therefore, critical in understanding the electrical load put on the power supply. This information MUST be provided if we are to be able to help.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 23, 2017, 02:36:34 pm
content: Voltage readings takenIn 4 different stages as you suggestedINPUT AC 234 VDISCONNECTEDVJK= 55.2V @ 0AUNLOADED (free spinning - just the motor shaft with nothing connected to it)VJK= 53.6V @ 0.05AVJK= 46V @ 1AVJK= 45V @ 1.19A MAXMax speed of motor was achieved at 1.19A i think thats why motor didn't ask for more currentAccording to that i think motor will draw more current to displace the load present on the vehicleTYPICAL LOAD (doing the work it would need to do to move a scooter with someone on it)VJK= 53.6V @ 0.05AVJK= 39V @ 2AVJK= 37V @ 2.6A MAXSTALLED (shaft prevented from rotating)VJK= 53.6V @ 0.05AVJK= 37.1V @ 2.7A MAXAs soon as the voltage reaches to 37V the motor stars all over again from 0 and gives a sudden jerk

author: IanB
author_rank: Super Contributor
timestamp: October 23, 2017, 03:00:17 pm
content: If I understood correctly you have a 24 V transformer in series with a 12 V transformer which would give a 36 V supply. And you have a voltage that drops to about 37 V when the motor is loaded. So your measurements seem entirely reasonable. I think you can ignore the measured 55 V when the motor is not drawing a load--this is a "fake" voltage produced by the capacitors.It might be interesting in fact to remove the capacitors from the circuit completely and repeat the measurements. Does the motor controller still work with no capacitors in the supply? I would guess the motor itself might work if connected directly to the supply without the controller.If you want to supply enough voltage to the motor and controller you will need a 48 V supply instead of a 36 V supply, which means you will need to put two 24 V transformer secondaries in series rather than 24 V and 12 V. But if you do this with the capacitors you will get nearly 70 V unloaded. You have to be careful about not exceeding the maximum voltage on the controller.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 23, 2017, 03:12:43 pm
content: Sir you have understood it correctlyI cannot connect the psu to the motor directly as it is an brushless dc motorI have tried two 24V transformers in series in earlier stages of testing the psuAnd you guessed it right it gave 74V as ouputAnd as soon as i connected that psu with controllerNo power was given to the motorthat's why i have used 24V and 12V in seriesMay be some security is present in the controller

author: IanB
author_rank: Super Contributor
timestamp: October 23, 2017, 05:34:00 pm
content: Have you tried the existing arrangement of 24 V and 12 V with no capacitors to find out if it works or not?

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 23, 2017, 05:36:26 pm
content: Not yetWill do it asapBut wouldn't it create a problem as too much ripple will be present in power supply

author: IanB
author_rank: Super Contributor
timestamp: October 23, 2017, 05:53:01 pm
content: Quote from: VickySalunkhe on October 23, 2017, 05:36:26 pmMaybe, maybe not. There is no way to know without trying it.

author: Brumby
author_rank: Unknown
timestamp: October 24, 2017, 01:23:00 am
content: With clear measurements, the issues are also much clearer.For the conditions specified, the power supply is performing pretty much as you might expect. The problem is that this power supply isnot appropriate for the need.When you look at the transformers, the voltages are given as 12V and 24V - which are AC voltages. AC voltages like this are typically given as RMS. If I skip quickly through the math, this means that you should only expect DC voltages of 12V and 24V when your power supply is operating at its rated load. Considering diode voltage drops and other circuit parameters, this supply is actually operating within reasonable expectations.The first point of understanding is that the "no load" voltage of VJK= 55.2V @ 0A relates to thepeakvoltage. The capacitors will charge up to this and keep the voltage high - but it is meaningless. It's like a weightlifter lifting only the bar - with no weights on it.The under load measurement of VJK= 37V @ 2.6A is a more realistic reflection on the demands of the load and the capabilities of the supply. However, as you have observed, at this voltage, the controller has a problem.This is the obvious solution -Quote from: IanB on October 23, 2017, 03:00:17 pmbut with onesignificantcaveat...QuoteThe answer is that your power supply needs to bevoltage regulated. The regulator must keep the voltage to a respectable level across a range of current - and allow the required current to pass.You might be asking yourself ...So why is this so hard?- and the answer lies in the normal mode of operation for which the scooter equipment was designed to operate - batteries. Four 12V, high capacity batteries will produce a reasonably stable 48V (nominal) over the range of current drawn by the motor. A simple unregulated supply will not do this (unless it wasmassivelyoverrated).To continue your project, you will need to regulate your supply - or run off batteries.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 24, 2017, 02:44:54 am
content: SirAt the very start onlyI thought to make a regulated power supplyFor which i have created a post for it alsoHere is the linkhttps://www.eevblog.com/forum/beginners/design-of-circuit-for-0-24v-5amp-regulated-power-supply/This is for half part of my psuIn this i have tried the regulated psuIt was running perfectly with loads other than motor like led, fan etc...But as soon as i have connected this psu with motor by switching the voltage level to 53Vas max voltage levels were 73VNo power was given to the motorBecause of which i thought to go for a simple way i.e, without regulated psuBut now which comes to a conclusion i have to move back to regulated psuSCHEMATIC IS ATTACHED FOR HALF PORTIONlm338 voltage regulator is used

author: Brumby
author_rank: Unknown
timestamp: October 24, 2017, 03:51:18 am
content: That circuit is very basic. Since you want to parallel two of these, there are more things to consider.Personally, I would take a different approach - but rather than muddy the waters with my thoughts, I will defer to those who have had more experience in building custom power supplies.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 24, 2017, 05:15:01 am
content: SirI would really like to know your approachAs i have searched a lot for regulated power supply for 48V 10ampBut i found no results for itAnd certainly results which were showing up were 24V 1ampThat's where this circuit belongs to just some changes with cap and voltage regulator were done.

author: IanB
author_rank: Super Contributor
timestamp: October 24, 2017, 05:27:05 am
content: Quote from: VickySalunkhe on October 24, 2017, 05:15:01 amThat's because it is not reasonable or practical to build such a supply from commonly available inexpensive parts or from simple instructions. In simple terms, it is not possible to make one.You can buy a switched-mode supply with those specifications that has been designed and engineered by a manufacturer with the necessary expertise, but you cannot make one yourself as a hobby project. I can't do it and you can't do it.So, to get what you require you need to obtain four 12 V lead-acid batteries and wire them in series to make 48 V. That will work, you can do it yourself with readily available parts, and it will perform exactly as required.

author: VickySalunkhe
author_rank: Regular Contributor
timestamp: October 24, 2017, 05:34:56 am
content: SirBut wouldn't it be a problem to lead acid battery to provide current of 13ampsAs I have read the configuration of lead acid battery which are available there output is about 1ampCan i draw more current from them without harming them?

author: IanB
author_rank: Super Contributor
timestamp: October 24, 2017, 06:10:57 am
content: It depends on the size of the battery. A car battery or a motorcycle battery can provide very high currents, up to hundreds of amps for short periods. Any moderately sized battery can provide 10 amps.