50Hz transformer experts? - Page 1
Forum section: electronics / projects

author: max_torque
author_rank: Super Contributor
timestamp: August 21, 2017, 09:36:04 am
content: Are there any 50Hz transformer experts loitering around here??I need the smallest possible (within practical limits) 150kW 400:460 Vac 3 phase stepup isolating transformer!! I think it'll need to be ODWF in order to get the power density up high enough. I have a source of cooling water at 5degC (and -30 degC if things get really serious....) which ought to help.Anyone have any experience with such a device??

author: oldway
author_rank: Super Contributor
timestamp: August 21, 2017, 10:29:34 am
content: The best program to developp such a project is here:http://www.rale.ch/If you don't want to buy one year use of the program for only one project, I suggest you to take contact with them or with one of their users/customers and ask to them if they could make this project for you.

author: Zero999
author_rank: Super Contributor
timestamp: August 21, 2017, 12:25:29 pm
content: Presumably it doesn't need to be isolated and an autotransformer will do? If so, it only needs to be the same size as a 22.5VA transformer. I doubt you'll be able to get something off the shelf. It will have to be bespoke.

author: ahbushnell
author_rank: Frequent Contributor
timestamp: August 21, 2017, 02:28:48 pm
content: Quote from: max_torque on August 21, 2017, 09:36:04 amUse a variable auto transformer.This one looks like it will work M6020-21Yhttp://www.variac.com/staco_480v_3ph_y.htmAndy

author: floobydust
author_rank: Super Contributor
timestamp: August 21, 2017, 06:29:23 pm
content: I think it's too expensive 150kW at only 400V. Because the currents are so high, windings are simply massive and difficult to construct.Usually you will go ahead (upstream) of the 400V transformer, and say 4-25kV down to 460VAC distribution transformer, which is off the shelf, common stock.Or cheaper to buy a load (i.e. motor) with the right voltage instead of convert.But 460V is 60Hz in North America, I had this hassle making something for global export.

author: Kleinstein
author_rank: Super Contributor
timestamp: August 21, 2017, 06:52:41 pm
content: An Autotransformer just for the missing 60 V would only be something like 22.5 kVA. So not that big. Still likely nothing to get of the shelf, but individually made. However in that power range individual voltages are not that unusual. It might end up as 3 single phase toroidal transformers. Extra cooling could help a lot with the power rating, but would be non standard at that low power. The power rating also depends of the isolation temperature rating.A thick wire would not be such a big problem - several parallel wires are an option. Conventional transformers might use kind of sheet material instead of wire.

author: max_torque
author_rank: Super Contributor
timestamp: August 21, 2017, 09:33:56 pm
content: Sorry, it can't be an autotransformer because i need galvanic isolation from supply ground!It also has to be 400/415 input as the facility it's going into is already wired, and has no extra room to stick a pre-transformer in thereWhat i really need is a basic pointer as to some typical iron core low frequency parameters, so i can estimate the core size as a starter?

author: drussell
author_rank: Super Contributor
timestamp: August 22, 2017, 04:04:21 am
content: Quote from: max_torque on August 21, 2017, 09:33:56 pmReally? You need anisolated150 kW, 400 -> 460 V transformer?You're screwed...That is going to be a massive, custom piece of expensive transformer!

author: Delta
author_rank: Super Contributor
timestamp: August 22, 2017, 07:23:24 am
content: I'm going to have to be nosey.... What is the application?150kW at 415v is an unusual ask!

author: richard.cs
author_rank: Super Contributor
timestamp: August 22, 2017, 09:21:42 am
content: It's simple enough to order a custom transformer for this, I have had something similar made before for work. You pay your money and a month or two later it arrives on a heavy-duty pallet.A quick online search found Eastern transformers (no connection to them, but they have more info on their website than some others).http://www.ete.co.uk/wp-content/uploads/2016/10/Page-13-Custom-Built-Range-of-Three-Phase-Transformers-Open-or-Enclosed-from-70kVA-to-500kVA-Class-F-and-Class-H.pdfTheir 150 kVA model is 700 x 470 x 850 mm and weighs 590 kg. Any 50 Hz transformer of this power rating will have a similar volume and weight, and most are this kind of 3-legged geometry. Depending on your load profile (phase balance, duration of max load, power factor) you might need a bigger one or be able to get away with something smaller. Oil cooled transformers are an option at this power level too. If the transformer is in continuous, long-term use then you might want to factor in the cost of the electrical losses which could be enough to justify a more expensive transformer.If you need the absolutely smallest/lightest setup then 3 torroidial transformers may be better, but you will struggle to find someone to make them that size. You're not going to be able to make a transformer like this for less than the pros, I would just email them (and a few others) for a quote (but be sure to be sat down when you read it).Are you by any chance running American 3-phase equipment in the UK? That fits your voltage ranges but doesn't explain the isolation requirement (which massively increases cost).

author: focovario
author_rank: Contributor
timestamp: August 22, 2017, 10:47:38 am
content: This guys (no relation, but I am familiar with their products):http://www.hunterdontransformer.com/isolation-transformers.htmlWill build exactly what you need. They have a lot of experience with water cooling, which will help for making a small footprint device.Make sure to specify the harmonic content of the load for K factor assessment.Good luck

author: max_torque
author_rank: Super Contributor
timestamp: August 22, 2017, 12:05:56 pm
content: Cost doesn't matter, and no, i'm not making it myself!I'm trying to establish if there is a hope-in-hell of fitting an isolation transformer into an existing bit of kit (a 150kW DC supply). It's currently connected to a 330kVA iso xformer, which is, as you would expect massive!It certainly doesn't need to be continuously rated, say 70% continuous and a max of 3min at peak power. It is going in a 'smart' system, so we can monitor temps / currents or what ever for safeguarding etcThe package space i have is under 50% of the size of the current 330kVA unit, so i need to push the limits somewhat, both in terms of winding I2R losses (oil to water cooling) but also probably in terms of core saturation (take a reduction in efficiency, as i have effectively an infinite supply to drive it from)

author: max_torque
author_rank: Super Contributor
timestamp: August 22, 2017, 12:08:56 pm
content: Quote from: Delta on August 22, 2017, 07:23:24 amLarge DC supply (150kW) and we parallel up 3 or 4 of them to give us 600kW of DC power for Powertrain testing purposes!

author: RGB255_0_0
author_rank: Frequent Contributor
timestamp: August 22, 2017, 12:17:06 pm
content: Formula-E by any chance?

author: Kleinstein
author_rank: Super Contributor
timestamp: August 22, 2017, 01:30:05 pm
content: In theory there is the option to do rectification and PFC at the 400 V input level (no isolation) and than do isolation with a much smaller higher frequency transformer, possibly together with some of the voltage regulation. At that power level one very likely would need PFC - likely active PFC to get it small.The transformer size is not that unusual - its about the size of distribution transformers and custom windings / voltages are not that special at this power level. So just ask a few of the manufacturers.

author: oldway
author_rank: Super Contributor
timestamp: August 22, 2017, 05:17:11 pm
content: I worked in the field of metro and train electric traction (choppers, rectifiers) and generally the rectifiers are 12 pulses for a better form of line current.So you need a transformer with 2 secundaries, one delta and another star.A rectifier of 150KW in 6 pulses ? this seems strange but not impossible.To solve your problem, the easiest way is to send to various transformer manufacturers all the technical specifications you have (NB: the power of a transformer is expressed in KVA's and not in KW's), including the dimensions of the space you have and ask for a quote.Each manufacturer will propose the technical solution that he considers the best.

author: max_torque
author_rank: Super Contributor
timestamp: August 22, 2017, 07:29:15 pm
content: Quote from: RGB255_0_0 on August 22, 2017, 12:17:06 pmNot directly in this case.....(although i actually was part of the team that developed the motor and inverter used for the first few racing seasons (and still used by some teams now) in FE for it's original application, which was the Mclaren P1 Hybrid Hyper-car)

author: PartialDischarge
author_rank: Super Contributor
timestamp: August 22, 2017, 07:43:04 pm
content: Talk to local transformer manufacturers.At work we have 80kW 420:380 transformers and they are not that big. Forget about oil/water cooling, price and complexity goes up and makes no sense for a test platform

author: CopperCone
author_rank: Super Contributor
timestamp: August 22, 2017, 07:56:32 pm
content: That's interesting. I wonder if the bulk of the copper required for the transformer operation actually acts as a heat sink, since the gauge is massive..the end result of the scaling is probably not very obvious to most people.I'm not sure if I ever saw a water cooled transformer before.

author: max_torque
author_rank: Super Contributor
timestamp: August 22, 2017, 09:51:24 pm
content: Quote from: MasterTech on August 22, 2017, 07:43:04 pmWater cooling makes sense for our platform, in fact it already uses it to cool the IGBT Array, the inductor on the back end DC:DC, and the front end rectifier. We happen to have a building with several thousand kW of cooling loops, at 25, 5, and -25 degC so we can use them to get a significant package benefit i think!The limiting factor is going to be the magnetic saturation, and hence drop in inductance as we attempt to push the iron volume down. This can be perhaps be offset by material choice and form factor of the lams / cores (although at 50hz, i doubt there's much to be had from things like minimised lam thicknesses etc?)

author: PartialDischarge
author_rank: Super Contributor
timestamp: August 23, 2017, 04:48:44 am
content: Suit yourself. Water cooling makes sense in igbt heat sink and maybe in ypur platform,but NOT in a 50Hz transformer where first you should reap benefits from frequency increases and efficiency increases/core reductions. Those are two totally different things but hey anything is possibleOut of curiosity what switching frequency are you using in those IGBTs?

author: oldway
author_rank: Super Contributor
timestamp: August 23, 2017, 07:14:49 am
content: No one can validly answer to your request for estimating the dimensions of the magnetic core without having all the necessary parameters and without having the dimensions of the available space.The complete design of the transformer must be made to verify whether or not it is possible to reduce the dimensions so that the transformer can fit in the available space.In a transformer project, there are many parameters that interfere with one another.That's the reason why I recomended to you to use the Rale program who permit you to modify the parameters as needed and to optimize your project.For example, the short circuit impedance is important because it affects the regulation of the secondary voltage ... With a short circuit impedance too high, you may have a secondary voltage too low at full load.Induction is limited to about 16Kgauss (1.6 Teslas) with high-quality magnetic lams (grains oriented 3.5% silicon) but it is necessary to take into account possible variations of mains voltage. (+/- 5%, +/- 10%, ...)

author: oldway
author_rank: Super Contributor
timestamp: August 24, 2017, 09:30:00 am
content: Some tips :Oil cooling is mainly used for high voltage transformers because the oil contributes to the insulation of the transformer.It is rarely used for low-voltage transformers.There is no gain in size because it is necessary to provide a waterproof case, a heat exchanger, which takes up a lot of space.There are other, more interesting alternatives.Firstly, it should be remembered that the thermal constant of a transformer is high, which makes it possible to overload a transformer for a limited time starting from a low temperature.Starting from a no load working transformer, you can easily overload a transformer up to 50% in addition to its rated power for about 15 minutes.By adding forced ventilation to an ordinary transformer, it can be overloaded by about 50% continuously.I have seen transformers specially built for forced air cooling (ventilation ducts between the windings) which allowed a 100% overload when the forced ventilation was switched on.For the size of the magnetic circuit, it is necessary to take advantage of the maximum possible space in height ... a distance of 5 to 10 cm is sufficient between the magnetic circuit and the steel sheets of the cabinet.

author: 2N3055
author_rank: Super Contributor
timestamp: August 24, 2017, 12:53:38 pm
content: You might want give this guys a call..https://www.koncar.hr/Proizvodi_i_usluge/TransformatoriNo affiliation, just an idea.. Maybe they can help...

author: oldway
author_rank: Super Contributor
timestamp: August 24, 2017, 01:24:26 pm
content: This one make special transformers as you need:http://www.jema.be/coil-winding?setlang=en

author: kridri
author_rank: Contributor
timestamp: August 24, 2017, 04:38:03 pm
content: Maybe you can connect two common used transformers back to back so 400V/15kV and 15kV to 400kV.But with the second transformer with his own 'regulator' so you can crank up the voltage a little bit to 460V.

author: oldway
author_rank: Super Contributor
timestamp: August 24, 2017, 07:23:44 pm
content: Quote from: max_torque on August 21, 2017, 09:36:04 amQuote from: kridri on August 24, 2017, 04:38:03 pmIn the reduced space where one transformer hardly fit, for sure, two will NEVER fit ....

author: mc172
author_rank: Frequent Contributor
timestamp: August 24, 2017, 07:56:07 pm
content: They might if you stack them.

author: oldway
author_rank: Super Contributor
timestamp: August 25, 2017, 07:17:42 am
content: Quote from: mc172 on August 24, 2017, 07:56:07 pmHow could you stack two transformers when the problem is to fit one in the available space ?

author: mc172
author_rank: Frequent Contributor
timestamp: August 25, 2017, 07:44:54 am
content: Well, that would be "to fit within the same available volume", wouldn't it.

author: oldway
author_rank: Super Contributor
timestamp: August 25, 2017, 08:28:11 am
content: My mother language is french, you are only making fun of google translation, that's not a very clever attitude.

author: Zero999
author_rank: Super Contributor
timestamp: August 25, 2017, 08:59:42 am
content: Quote from: oldway on August 25, 2017, 08:28:11 amI agree. It's silly. I knew what you meant. It's common sense. Two transformers will take up more space, than a single one and the chief requirement was for it to be as small as possible.Unfortunately no dimensions were given by the original poster. There's also a limit to small a 50Hz transformer, of a certain power rating, can be, due to physics. One way round this would be to chop the input voltage to a higher frequency, pass it through a smaller, high frequency transformer, then rectify it and pass it through an inverter and filter to get it back to 50Hz.

author: oldway
author_rank: Super Contributor
timestamp: August 25, 2017, 10:08:28 am
content: As is often the case on this forum, max_torque does not provide the information needed to be able to provide a solution to its problem.Already and to begin with, we NEVER specify the power of a transformer 50Hz in KW's but only in KVA's, demonstrating that max_torque does not even know the most basic concepts in transformers designSo, he should give us all the information possible because with the little information he gives us, we are obliged to guess.That's not the way I like to work. I need technical data and specifications.1) The power of 150KW? Where does this value come from? We can guess that this transformer will be used to power a power supply of 150KW and that the load is probably a three-phase rectifier bridge.The power is then certainly much higher than 150KVA's.How many ? A measurement of the RMS current per phase made on the current 330KVA's transformer with full load of the 150KW power supply would be very useful.2) the volume available? What forms and dimensions? A drawing would be welcome. Where is this volume? In the 150KW power supply cabinet? Does this cabinet have forced ventilation? Is it possible to install forced ventilation in the available volume?3) the operating conditions of the transformer? Max_torque has already given some explanations, but it would be necessary to be more precise on the most demanding conditions.4) What's the maximum mains voltage possible ?NB: If you are not satisfied with my bad english, thank you for complaining to google translation.I only assume the technical point of view of my posts.

author: mc172
author_rank: Frequent Contributor
timestamp: August 25, 2017, 11:17:56 am
content: Quote from: oldway on August 25, 2017, 08:28:11 amWhat a retarded comment. I wasn't making fun of your English, I was saying that if he absolutely had to fit it in the same volume he'd have said "to fit within the same volume". Most of the time people are concerned about floor area, not the volume of air above the device, which is largely unused.If you're using and relying on Google Translate, how do you know to use the term "an" in front of "HP1740A" in other posts?

author: oldway
author_rank: Super Contributor
timestamp: August 25, 2017, 01:03:54 pm
content: In french, people say : le transformateur doit pouvoir être placé dansl'espacedisponible, so I did not feel nothing wrong with translation of Google ....I read fluently tecnical english but this does not means that I speak and write also fluently english.I learned english at school many years ago and I still remember of some tips, but not enough to write without help of Google translation.I used an in front of HP1740A because I read this in technical papers, that does not proove nothing about my knowledge of english.When people say : I need the smallest possible (within practical limits) 150kW 400:460 Vac 3 phase stepup isolating transformer!!, that means that ALL the dimensions must be the smallest possible, the height too. No floor area here... !If there is one post in this topic who his a retarded comment, it is well your post...

author: oldway
author_rank: Super Contributor
timestamp: August 25, 2017, 02:22:47 pm
content: And still another solution of the problem: an external three phase frequency converter 50Hz - 400Hz 200KVA's and a 400Hz three phase isolating transformer who will fit for sure in the little volume available.http://www.mak-powersis.de/200-kva-frequency-converter.html

author: Jeroen3
author_rank: Super Contributor
timestamp: August 25, 2017, 04:10:47 pm
content: You would need to ask companies that wind them at customer request. Like Belpa or Drie Transfomatoren.But if it is to make DC, a plain 50 hz one might not be the best option. You can get them with phases offset to get more pulses.You could also check if a 400 Hz rotary converter fits the space.

author: Zero999
author_rank: Super Contributor
timestamp: August 25, 2017, 05:38:47 pm
content: Quote from: Jeroen3 on August 25, 2017, 04:10:47 pmWho said anything about a rotary converter? That's not how it's done these days! An inverter, consisting of IGBTs, is used to increase the frequency. I wouldn't recommend 400Hz. I'd go as high as is practical before the skin effect becomes a significant factor.

author: Jeroen3
author_rank: Super Contributor
timestamp: August 25, 2017, 09:41:39 pm
content: Think outside the box. Isolated supply was requested for high power low voltage DC.Apparently there are space constraints. With a rotary converter you have a different space footprint than transformer.Also, big chunks of copper are less destructible then anything with semiconductors.

author: oldway
author_rank: Super Contributor
timestamp: August 26, 2017, 09:41:40 am
content: Quote from: max_torque on August 22, 2017, 12:05:56 pmFor me, what max_torque wants to do is clear.He wants to remove the current transformer of 330Kva that is outside the 150KW power supply (probably to save space) and replace it with a transformer placed inside the cabinet of the 150KW power supply.The volume available in this cabinet is 50% that of the current transformer of 330KVA's.Therefore, any solution proposal with equipment placed outside of the cabinet is of no interest.In summary, to solve this problem, we need to:1) Measure theRMSline current of the 330KVA transformer with the fully loaded power supply to determine the maximum power in KVA's actually consumed.2) determine the maximum conditions of use. (Load x duration)3) check whether forced ventilation is possible or not (depends on the 150KW power supply cabinet, we have no details about it ... what brand, what model?) If possible, what's the cold air max temperature ?4) it is necessary to have a drawing of the available volume with the max. dimensions.5) What are the network voltage specifications?6 ) What is the load of the transformer? Bridge rectifier? What kind of filtering? Head Capacitor or head Inductor?7) what are the acceptable variations of the secondary voltage at idle / full load?8 ) What are the characteristics of the current 330 KVA's transformer? (Copy or picture of transformer nameplate.)9) Pictures of the 150KW power supply, with door of the cabinet open.