Generator Excitation Current

[MKPower]

I have a client that is installing a very old refurbished hydro generator that is missing the excitation nameplate. Does anyone have any rules of thumb or ideas how to calculate the required excitation current for a 200 kW, 2400 Volt generator? (This is not a self excited, so a small static exciter will be used).

 

[EddyEE]

1. Get the static exciter field resistance.
2. Run the unit at rated speed.
3. Get the no-load excitation voltage by applying dc voltage (from a battery) gradually to the static exciter field until you get the rated output of 2400Vac.
4. Compute the excitation current at no-load based on your results in 1 and 3.
5. Voltage regulators are normally rated at 32Vdc, 63Vdc, 125Vdc and 250Vdc. Current ratings varies but at least you will now have an idea on what your full-load excitation voltage and current probably are. (Ex. If the result in 3 is less than 12Vdc, you may use an AVR with 32Vdc rated output)

For more information, try to visit

http://www.basler.com

Regards,

Choi

(This is my personal knowledge and I'm not connected to Basler Electric company.)

 

[MKPower]

Thanks FilipinoEE.

I am aware of the no load test (I have a faint memory from college machine lab) and thank you for you insight. I was hoping there might be some other ways to estimate the requirements since the client wants to install electrical equipment prior to commissioning the unit. Perhaps we'll just have to wait and do the no load test first though.

MKPower

 

[EddyEE]

I think the problem is sizing/selecting a new voltage regulator. Have you tried looking at

http://www.basler.com?

While waiting, why not try to contact the generator manufacturer or other manufacturers of similar equipment? You will definitely get a better answer from them and may even provide you with catalogues/manuals.

Actually, servicing generator sets is my job 7years ago and I'm kind of rusty. Although, I left all my notes, books, catalogues and manuals back in my home country, I'm very much willing to share what is left in my memory.

Regards.

 

[MKPower]

FilipinoEE:

I am very familiar with Basler equipment. My client is leaning toward using a very simple (cheap) DC rectifier to excite the field - no AVR. However, if it turns out that the excitation requirements are quite small, we may use a Basler DECS-200 unit including AVR.

These units are quite old (1940's to 1950's vintage) and have been rewound at least once. Documentation searches for Westinghouse Canandian prints have not been sucessful. I think we will just have to perform the no load excitation test and go from there.

Thanks again,
MKPower

 

[boomsystems]

It is very difficult to estimate excitation current for old generators as provision of airgap in old machine was very liberal. Simple way is to check the panel meters if they are available luckily at original site. For a similar generator we encountered the field current was 140A at 56V. But it is still difficult to say the exact value. Good luck to you.

 

[MKPower]

boomsystems:

Thanks for the tip on looking at the meters. These units were removed from another site, but I will see if anyone took pictures of existing control cabinets.