Where can I find common parameters of power transformers?

[Zrakk]

As common I mean inductances and eq resistances. I've been searching for high voltage transformers (to use with a 12-pulse rectifier) but I only see catalogues just trying to sell the thing. Do you have any recommendation as a book or another reference?.

Thanks in advance!

 

[davenn]

but I only see catalogues just trying to sell the thing. Do you have any recommendation as a book or another reference?.

Pick a suitable transformer you see in a catalog
then do google searching for datasheet for that make and model, it's what we all have to do for any device.. transformer, resistor, capacitor' transistor, IC etc

 

[SunThief]

Just a guess... maybe throw in the phrase "Transformer test report" during your searches...

 

[Hoo]

Manufacturers rarely provide detailed information on that. I have not seen it in catalogs or product data cutsheets with for example Eaton or Schneider Electric. I think you will have to call them.

 

[Mandy D]

I design transformers and, in the case of power transformers such as would feed a 12 pulse rectifier, we rarely work out the inductance. The resistance of the windings is only used to calculate the losses and not published. On most transformers you will find a % regulation, which is largely determined by the winding resistances of the primary and secondary. On large transformers you will see % reactance which relates to the inductance of the windings.

My main reference book is the J&P Transformer Book. It discusses the design of transformers (delta/delta and delta/wye) for use with 12 pulse rectifiers. Remember that you can only ever approximate the design because of the sqrt 3 factor that relates wye and delta windings. Use the book to determine a specification for your transformers and approach an independent transformer manufacturer.

 

[Zrakk]

I design transformers and, in the case of power transformers such as would feed a 12 pulse rectifier, we rarely work out the inductance. The resistance of the windings is only used to calculate the losses and not published. On most transformers you will find a % regulation, which is largely determined by the winding resistances of the primary and secondary. On large transformers you will see % reactance which relates to the inductance of the windings.

Thanks a lot for your answer. So, in order to ask a manufacturer, should I need the following parameters right?:

• Rated Power - Sn
• Rated Voltage - Un
• Rated Freq - Fn

Also, citing from J&P Transformer Book, 13ed. I can assume Un > 400 kV.

"In both cases, however, system interconnections are usually made at those points on the AC systems having the highest voltage level, so that the 'AC windings' of converter transformers are normally of 400 kV or higher."

Therefore, telling them these three parameters (Sn > 200 MVA, Un > 400 kV and Fn = 50 Hz) they should be able to give me at least load and no-load losses as well as short circuit voltage (Ucc) in order to let me calculate or estimate winding resistance and leakage inductance? Should I specify another parameter? I want to emphasize that it isn't necessary for my purpose to include all transformer specs as the main focus of my investigation would be in a power electronics circuits which is at the DC side of the system (after 12-pulse rectification).

Again, thank you very much!

 

[Mandy D]

Thanks a lot for your answer. So, in order to ask a manufacturer, should I need the following parameters right?:

• Rated Power - Sn
• Rated Voltage - Un
• Rated Freq - Fn

Also, citing from J&P Transformer Book, 13ed. I can assume Un > 400 kV.

"In both cases, however, system interconnections are usually made at those points on the AC systems having the highest voltage level, so that the 'AC windings' of converter transformers are normally of 400 kV or higher."

Therefore, telling them these three parameters (Sn > 200 MVA, Un > 400 kV and Fn = 50 Hz) they should be able to give me at least load and no-load losses as well as short circuit voltage (Ucc) in order to let me calculate or estimate winding resistance and leakage inductance? Should I specify another parameter? I want to emphasize that it isn't necessary for my purpose to include all transformer specs as the main focus of my investigation would be in a power electronics circuits which is at the DC side of the system (after 12-pulse rectification).

Again, thank you very much!

Hi Zrakk

With a transformer of the size and specification you are proposing, the manufacturer will likely provide all or most of that information in their proposal as most applications will require it. They will, obviously, want the primary and secondary voltages and the vector group, too. If you have load and no-load losses you can calculate the effective a.c. resistance, which is different to the d.c. resistance due to skin effect in copper.

That is a lot of d.c. power. Are you looking at d.c. links between a.c. networks?

 

[Windadct]

Is this an academic exercise - or are you really looking to source this? - In addition to the questions and issues above, there are a whole other set of issues relating to the exceptionally high voltage, AND the V and I harmonics involved in rectifiers. While the 12 Pulse helps on both the line and load side, the transformer windings do not get this benefit - the effects if high dI/dT and dV/dT -
Properly specifying the winding type and insulation techniques, and leaning on the supplier for a lifetime estimate, guarantee or warranty become very complex issues, that require very specific experience. I would hazard to say there may only be 10 -12 people experienced with making a > 250KV rectifier transformer for production.
Then - the harmonics issues will also affect the losses, so the loading of the transformer, and the various load configurations, and input - output filters will affect the losses in the transformer.
I guess my point is there are not "common parameters" for such an uncommon product.

 

[Zrakk]

Hi Zrakk
That is a lot of d.c. power. Are you looking at d.c. links between a.c. networks?

Is this an academic exercise - or are you really looking to source this? - In addition to the questions and issues above, there are a whole other set of issues relating to the exceptionally high voltage, AND the V and I harmonics involved in rectifiers. Properly specifying the winding type and insulation techniques, and leaning on the supplier for a lifetime estimate, guarantee or warranty become very complex issues, that require very specific experience. I would hazard to say there may only be 10 -12 people experienced with making a > 250KV rectifier transformer for production.
I guess my point is there are not "common parameters" for such an uncommon product.

Mandy D.- Exactly. I'm doing an investigation of a circuit -S1 and S2- located between rectifier output and DC link in order to transmit a lot of power between a.c. networks (point-to-point configuration).

Windadct.- As you can see in the circuit linked above (S1 and S2), at that time I specified a three-phase 3-wdg transformer which know I think it is unfeasible because of transportation. However, I've seen a lot of single-phase 3 wdg transformers (http://www02.abb.com/global/seitp/seitp202.nsf/0/be0fae657152c39dc125803d0012dd70/$file/HVDC+converter+transformers.pdf for example) with its primary windings rated over 345 kV and secondaries between 122 kV and 240 kV. This is why I thought it wasn't uncommon.

Finally, my investigation is about those S1 and S2 circuits specifically so I could easily define 1e-9 as inductances for every winding of an imaginary transformer and my simulation on PLECS will run without any problem. However, I prefer to include actual values but know I'm a bit confused as I've seen examples like ABB that converter transformers actually exist but at the same time with your answer I understand it will be very difficult to obtain these parameters. And again, insulation techniques, winding type or warranty won't be a part of my investigation. Maybe in the future I'll include them as core losses or proper design for lab experimentation.

In case it is almost impossible, would it be more reasonable to search for power transformers instead of converter transformers parameters?

Thanks to both of you!

EDIT: I'd like to add this Tokyo-Chubu HVDC Interconnection Project with two 3-ph 3-wdg transformer of 560 MVA, 154kV/87kV