3-phase power supply - Page 1
Forum section: electronics / projects

author: S. Petrukhin
author_rank: Super Contributor
timestamp: November 06, 2020, 12:20:43 am
content: Dear friends,I need to develop a low-power supply with an input voltage of 380V AC (540V DC).Find it difficult to choose the components of the high part: the chip, the transformer. I don't know much about this topic.This must be a line-voltage-rated power supply, without using zero, not 230V AC.Can you recommend any solutions?Maybe there are ready-made modules?Parameters:input voltage 3 phase 380V ACoutput voltage 24V DC 1A

author: drvtech
author_rank: Regular Contributor
timestamp: November 06, 2020, 12:53:05 am
content: You might find it difficult to get such a small (24watt) one but this one fits the bill and is pretty good value considering the spechttps://www.mouser.co.uk/ProductDetail/Delta-Electronics/DRP024V120W3BN?qs=Paqgc3NkMbQ5gVgkTVnbOg%3D%3D

author: S. Petrukhin
author_rank: Super Contributor
timestamp: November 06, 2020, 01:00:11 am
content: Quote from: drvtech on November 06, 2020, 12:53:05 amThanks!But sorry, I didn't specify: I don't need a ready-made device, I need a module for a PCB or a circuit diagram.

author: sandalcandal
author_rank: Unknown
timestamp: November 06, 2020, 01:46:53 am
content: Given its such a low power requirement, is there any hard reason you can't just use a single phase to neutral and then just use a standard single phase module?Edit: Sorry, didn't realise request was specifically for a no neutral, delta only system.

author: drvtech
author_rank: Regular Contributor
timestamp: November 06, 2020, 09:22:41 am
content: He said "without using zero" which I take to mean "neutral" so I guess it's a delta only supply. Still, it's no different from a 230V supply except that the reservoir capacitors, rectifier and switching transistor and a few other components need to be suitably rated for the higher voltage.Edit - should have included the transformer in that list. Of course, if neutral is available then all you need is a standard circuit with a different bridge

author: Circlotron
author_rank: Super Contributor
timestamp: November 06, 2020, 09:31:16 am
content: For a 540V DC buss I'd see about using a half bridge.

author: Miyuki
author_rank: Frequent Contributor
timestamp: November 06, 2020, 09:50:43 am
content: Quote from: drvtech on November 06, 2020, 09:22:41 amExactly, today are plenty of 1200V or higher voltage transistorsJust take any flyback and use a higher voltage transistorTransformer can remain (if have enough insulation), just change output rectifier to higher ratingNo big deal, just keep insulation distances high//editand for brave enough just order some Chinese ones, they have 400V versions of that small bare board AC/DC

author: Jeroen3
author_rank: Super Contributor
timestamp: November 06, 2020, 09:59:18 am
content: Quote from: S. Petrukhin on November 06, 2020, 12:20:43 amST has some parts in their VIPER series, but you're pushing it quite high that internal fets may not be feasable anymore.TI also has many controller for this. Id recommend browsing through their catalog of reference designs to learn more theory.Then buy an eval board and slowly merge it to your design.This is a challenging endeavor, much cheaper and faster to use a off the shelf supply unit.Ready-made board modules for this are very rare. But they do exist.CUI AE40-UW-S24

author: S. Petrukhin
author_rank: Super Contributor
timestamp: November 06, 2020, 03:07:27 pm
content: Quote from: Circlotron on November 06, 2020, 09:31:16 amI do not know how to make a half-bridge in a 3-phase triangle.In addition, the half-bridge will still give an amplitude value of 540V.

author: m k
author_rank: Super Contributor
timestamp: November 06, 2020, 03:20:12 pm
content: Don't use a triangle, two phases are enough.24W is not so much.Is primary side passive attenuator out of the question?

author: S. Petrukhin
author_rank: Super Contributor
timestamp: November 06, 2020, 03:33:19 pm
content: Quote from: Jeroen3 on November 06, 2020, 09:59:18 amInternal fet more than 400B I have not seen, maybe not really understood the variety.Perhaps the power part and the controller are not too scary for me, but the transformer is a disaster. I can't use an ordinary transformer that is used for 230V converters, isn't it?The module you proposed is good, it would fit me completely, but the price is like for half an airplane wing.What do you think, if I use capacitors instead of diodes in a three-phase rectifier, will I get a C-voltage divider?

author: S. Petrukhin
author_rank: Super Contributor
timestamp: November 06, 2020, 03:38:09 pm
content: Quote from: m k on November 06, 2020, 03:20:12 pmBetween the two phases, the line voltage is 380V (540v amplitude), I can't count on a phase voltage of 230V (310V amplitude) because the device will be installed on the side of the motor where have not neutral core in the wire.I would like an honest power supply, isolated. And I don't really understand what is passive attenuator. Approximately as I suggested in the previous message?

author: themadhippy
author_rank: Super Contributor
timestamp: November 06, 2020, 03:56:29 pm
content: Quoteuse a suitable rated tranny,380/415v primary to 24v is not a rare beasty for examplehttps://www.ete.co.uk/product/transformer-380v-480v-to-24v-or-48v-50va-wide-input-voltage/or if your feeling brave a 240v to 15v tranny is roughly the same ratio as 380 to 24

author: S. Petrukhin
author_rank: Super Contributor
timestamp: November 06, 2020, 03:59:24 pm
content: Quote from: themadhippy on November 06, 2020, 03:56:29 pmNo, no, that much iron won't fit in my device.

author: S. Petrukhin
author_rank: Super Contributor
timestamp: November 06, 2020, 04:03:20 pm
content: What do you think about the serial connection of the windings of a 310V switching transformer used for switching power supplies in a 230V one phase network?

author: Miyuki
author_rank: Frequent Contributor
timestamp: November 06, 2020, 04:07:09 pm
content: Cheapest way ...https://www.aliexpress.com/item/32762537667.html?spm=a2g0o.productlist.0.0.7e676be8WHm8We&algo_pvid=f4b086f0-7927-4515-8b3e-87e183c633b1&algo_expid=f4b086f0-7927-4515-8b3e-87e183c633b1-28&btsid=2100bdcf16046786394757810ea4c0&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

author: akimpowerscr
author_rank: Regular Contributor
timestamp: November 06, 2020, 04:54:32 pm
content: Quite simple and cheap with 3 little transformers for printboard 230V/18V 10VA...https://fr.rs-online.com/web/p/transformateurs-pour-circuit-imprime/1707360/

author: akimpowerscr
author_rank: Regular Contributor
timestamp: November 06, 2020, 05:28:42 pm
content: A little explanation for who's are not electricians:The primaries of the three single-phase transformers are star-connected.There is no need for a neutral because the load is balanced.Each primary therefore receives a voltage of 380V / 1.73 = 219VThe secondaries are delta-connected to balance the currents and eliminate harmonics 3.The secondary voltage will be 18V x 219/230 = 17.1VcaThe rectified voltage will be 17.1Vca x 1.41 - 1.2V = 22.9VIf this voltage is insufficient, we can choose a secondary voltage of the transformers of 20V instead of 18V

author: S. Petrukhin
author_rank: Super Contributor
timestamp: November 06, 2020, 05:48:29 pm
content: Quote from: akimpowerscr on November 06, 2020, 04:54:32 pmThanks!It is a great idea to connect the transformers at the input according to the "star" scheme. But this is an expensive German manufacturer, and it will be difficult to get its products in Russia. Miniature transformers at 50 Hz are generally a rare device.

author: akimpowerscr
author_rank: Regular Contributor
timestamp: November 06, 2020, 06:24:47 pm
content: The link I gave is just one example, there are dozens if not hundreds of manufacturers of miniature transformers.These 50Hz transformers are found in many equipment.It would surprise me very much that it is not found in Russia.You should also know how many power supplies you expect to produce and sell.If it's 10 units you won't be able to negotiate the components you buy, if it's 10,000 it can all be very different.At a minimum, before rejecting a solution, you should make a serious analysis of what is available on the market and consult with Russian manufacturers of transformers.

author: S. Petrukhin
author_rank: Super Contributor
timestamp: November 06, 2020, 06:48:26 pm
content: Quote from: akimpowerscr on November 06, 2020, 06:24:47 pmThey are available from different sellers in Russia, but the price of three such transformers is more than the price of everything else in device. And these are unreliable suppliers: today they have a few pieces, and then wait six months for delivery. Unfortunately, we don't have our own Mouser, Farnell, DigiKey. Russian retailers are very lazy - they do not even bother to sell 1000 PCs. In fact, the only reliable and affordable supplier is LCSC.I am developing a motor protection unit, I need power for several sensors, buttons, lamps. This is an unjustifiably high price.

author: Jeroen3
author_rank: Super Contributor
timestamp: November 06, 2020, 07:07:29 pm
content: The three transformers is the simplest way to do it. Although heavy.I didn't notice you were in russia, this probably makes the flyback approach very difficult to do since the many export restrictions on parts of US vendors.However, russia does have access to the chinese market, right? So transformers or flyback controllers could be sourced there?

author: akimpowerscr
author_rank: Regular Contributor
timestamp: November 06, 2020, 07:13:29 pm
content: The advantage of the power supply that I proposed is that it is very reliable, especially with the transformer of the link which is of high quality and which meets the standards EN60742, VDE 0551, IEC 61558.If it is a power supply intended to supply sensors, one cannot skimp on the quality, nor on the reliability.With a switching solution, given the high rectified voltage (540Vcc) it will be very difficult to achieve a reliable power supply, especially for low power (24W).

author: akimpowerscr
author_rank: Regular Contributor
timestamp: November 06, 2020, 07:29:34 pm
content: QuoteThat's not right.The power supply is the most important item , if it fail, all will stop working.How much cost every hour of brealdown?How much cost to replace and to repair the power supply ?So it MUST be very reliable and that justify an eventual high price.

author: akimpowerscr
author_rank: Regular Contributor
timestamp: November 06, 2020, 08:18:48 pm
content: If you choose the decoupage solution, such a power supply will certainly not be cheap.You will need to protect it against power surges and transients.There must be a tolerance of + 10% of the network voltage, so a rectified voltage can reach 594V1) to protect the rectifier diodes against industrial electrical network transients, 3 x 50Hz protection induxtances should be placed at the input.2) with such a high dc voltage, the best configuration in order not to stress the components too much (transformer, semiconductors) is the forward configuration with 2 switches with reset of the core.https://www.onsemi.cn/pub/Collateral/TND378-D.PDFThe voltages in a flyback configuration are too high especially since the dimensions of a 25W ferrite transformer are very small.You will need to use quality components which will not come cheap.NB: I apologize to the moderators for having published 3 answers by following, but I did it for clarity because they relate to 3 very distinct points of view

author: m k
author_rank: Super Contributor
timestamp: November 06, 2020, 08:44:08 pm
content: Quote from: S. Petrukhin on November 06, 2020, 03:38:09 pmIt's a resistance for eating excess power.In your case what ever is needed to drop your transformer's primary to 230V.You're already thinking serial transformers, that is much better.

author: S. Petrukhin
author_rank: Super Contributor
timestamp: November 06, 2020, 08:53:34 pm
content: Quote from: akimpowerscr on November 06, 2020, 07:29:34 pmThank you for your detailed statement!When we have the opportunity to justify a high price, we use Siemens equipment - they make the most of the "most expensive" pricing policy. But I will tell you terrible words: very expensive Siemens power supplies (by the way, pulse even for 3A), developed by good engineers in high-quality production, from expensive components, in compliance with all standards and theoretical research, and even the phases of the moon, fail and not infrequently. All equipment fails, and risk management and sustainability are another topic.I will tell you my opinion: the presence of spare parts for quick replacement solves most problems. Some of the most important parts of the equipment are duplicated. I don't automate nuclear reactors or pacemakers.I'm not saying that using transformers is bad, it's great, but it's not wise in my situation.

author: Circlotron
author_rank: Super Contributor
timestamp: November 06, 2020, 09:34:11 pm
content: Quote from: S. Petrukhin on November 06, 2020, 03:07:27 pmWith a half bridge converter the two mosfets will only see 540V maximum. With a single mosfet fly back or forward converter the single mosfet will see about 1080V maximum approximately.

author: Circlotron
author_rank: Super Contributor
timestamp: November 06, 2020, 09:37:15 pm
content: Also, I hope your device is not on the motor side of the contactor. If it is, when the motor is switched off it’s inductance will produce big voltage spikes! That could break whatever is connected across the motor wires.

author: akimpowerscr
author_rank: Regular Contributor
timestamp: November 06, 2020, 10:04:00 pm
content: QuoteAs I explained, a switching power supply, in an industrial environment and connected to an industrial electrical network 3 x 380V can never have the same reliability as a simple power supply with three transformers, as I proposed, even if this power supply is designed by Siemens.If a switching power supply designed by Siemens often breaks down, what about the one you are going to design on the basis on informations of a forum and with pirated/fake parts bought in Russia !!!!In power electronics, reliability is first a question of quantity of power components ... then by the level of technology of those power components.....The 50Hz transformer solution is unbeatable on these points.Lower quantity of components, technology perfectly mastered.The assumption you make that all equipment fail, without regard for MTBF (Mean time between failure) shocks me deeply because I have worked in the field of quality control and what you are saying is non sense.

author: sandalcandal
author_rank: Unknown
timestamp: November 06, 2020, 11:24:18 pm
content: Quote from: S. Petrukhin on November 06, 2020, 03:33:19 pmThe capacitive divider type power supply or resistive divider m k was also suggesting (or a combination) is probably worse than a transformer in terms of cost. With a fixed 24V 1A load you'll need quite a large capacitor (in terms of AC mains capacitors) or a very high power resistor. Somewhere near 350W for a dropping resistor or 10uF for a mains rated dropping capacitor. I think you'll find the size, weight and cost for such parts far outweighs the solution akimpowerscr suggested.Even using a capacitor dropper you'll still have 350W in reactive power and you'll need to make sure the mains connections feeding the circuit can handle an extra 350W load.If the load can go lower than 1A at any time you'll need to add a dummy load to prevent the voltage rising too high which will at the same time will increase the size of the dropping/attenuating element. For 20% change in voltage over 0% load vs 100% load: you'll need a dummy load such that total load impedance only changes by ~20% thus the dummy will need to be about 5 times higher than the actual load, the dropping element will also need to drop 5 times the power thus you'll need a 1750W resistor or 50uF capacitor. The connection supplying your motor + 24W power supply will of course now need to handle an extra 1750W.Edit: You could also use a 24W linear regulator circuit rather than a passive dummy load but that'll only take you back to 350W dropping.On top of this you have the much more dangerous failure modes of such a non-galvanically isolated system.There is good reason you only see mains level capacitive droppers are used in the cheapest low power LED power supplies.If you need something more compact than the mains frequency transformer solution akimpowerscr suggested you'll need to look at HF switching circuits which people have mentioned but they will definitely be more prone to failure and no guarantee to be cheaper overall. I don't think it will be too difficult to find suppliers in China that can make transformers you require. Cheap non certified example:https://www.alibaba.com/product-detail/30VA-3-phase-synchronous-signal-transformer_60267402663.htmlAs my great grandpa would say: Good thing no cheap - cheap thing no good

author: S. Petrukhin
author_rank: Super Contributor
timestamp: November 07, 2020, 08:04:52 am
content: Quote from: sandalcandal on November 06, 2020, 11:24:18 pmI did not mean direct reduction of capacitors to 24V. I see this as an opportunity to lower the primary voltage for the switching power supply to use the common 230V design.

author: S. Petrukhin
author_rank: Super Contributor
timestamp: November 07, 2020, 08:50:02 am
content: Quote from: akimpowerscr on November 06, 2020, 10:04:00 pmI probably can't explain it well enough in English and you don't understand what I'm talking about.The availability of components and their price are equally important for reliability. I hope you understand that there are not only extreme options, but also optimal solutions. Probably, I would like to have wires made of gold and it would be very good, but it is expensive and inaccessible, will remain in my dreams. I can choose expensive and bulky components, puff out my cheeks and say I'm cool, and they will say: sorry, the segment of expensive solutions is occupied by Siemens and they have disproportionately more resources to capture the market.And please don't tell me about European bureaucracy. About different control systems, etc. They are often funny and have a goal for the sake of a goal, disconnected from real life, just someone good work to report.I have a question of finding a base solution that will be tested and upgraded.This is the normal way of development: learning from experience and existing solutions.

author: akimpowerscr
author_rank: Regular Contributor
timestamp: November 07, 2020, 10:16:32 am
content: QuoteYes, without a doubt, standards are useless, they are just "bureaucracy".Sorry, there is an obvious incompatibility between your views and mine, if not with European views and it is impossible to continue a dialogue under these conditions.I'm talking about 3 miniature transformers that can be found everywhere for less than ten euros and you are telling me about gold wires ......I think we have reached the bottom of the pit of absurdity.I stop participating in this topic, good luck.

author: poorchava
author_rank: Super Contributor
timestamp: November 07, 2020, 10:20:48 am
content: Given the circumstances I'd try designing a flyback around some 1200 or 1700V mosfet.Flyback design IMO has more tradeoffs and formula juggling than other topologies. You basically need to design it in such a way that vbus + vout * transformer_ratio (=vrefl) + some 100...200V margon does not exceed the mosfet rated vdsmax.You may even look into SiC, since you'll end up with much less power dissipated in the snubber circuit. You may also go for snubber less design, but that usually requires a higher voltage mosfet or designing for lower vrefl.

author: sandalcandal
author_rank: Unknown
timestamp: November 07, 2020, 10:51:54 am
content: Quote from: S. Petrukhin on November 07, 2020, 08:04:52 amYou're still looking at a drop of 150W and the capacitive option will probably be incompatible in that case.

author: S. Petrukhin
author_rank: Super Contributor
timestamp: November 07, 2020, 11:51:56 am
content: Quote from: sandalcandal on November 07, 2020, 10:51:54 amI think the voltage drop here can be anything. A capacitor divider is a common divider based only on reactance. This is more affected by current restrictions and shunting one side of the load. And these capacitors will be quite bulky. I've done some calculations, so I probably won't have to use this idea.

author: Pawelr98
author_rank: Regular Contributor
timestamp: November 08, 2020, 11:55:09 pm
content: Half-bridge would be the simplest one to build."Standard" transistors can be used and it can be really crude in design.The main problem would be the voltage headroom for the driver.Most can only withstand 600-650V DC which is close.Which means either some kind of overvoltage protection/clamp or driving through transformer.There are 1200V drivers but they are much harder to obtain.This is where flyback / single transistor forward are better, as they only require low-side switching.Half-bridge on the other hand doesn't need any fancy feedback.In some cases feedback-less operation is possible (such as the known IR2153 or similar), depends on the 24V rail stability requirement.IRS2166 can be used as it has overcurrent protection.It's a ballast driver but otherwise can be used as a halfbridge driver.EOL/SD clamped to ~2V (red LED) should be enough to make it run.Flyback/Forward just requires a high voltage mosfet that can withstand way over 1kV.Otherwise a cheap UC3842/45 (or any other jellybean chip) can be used.Another idea would be to buy a 1600V thyristor and make it fire when sine wave passes 350V for the second time (sine wave goes to 540V peak, then goes down to 350V and this is when the SCR fires).Capacitor would get charged to 350V maximum and standard design could be used.The problem is that if the SCR shorts, everything blows up.