Input kVA needed for AC dielelectric testing

[VLFit]

When perfroming a high voltage AC test on a motor, the capacitance or the mA current draw at test voltage must be known to properly size a test set. Is there any guidline out there that tells how many kVA of 60Hz AC power is needed for a hipot test on the average size motors? Right now I have a 12,000 HP 13.8 kV motor to hipot. I know that's not enough info but, for example, will it need 2 kVA or 20 kVA at the test voltage of 25kVac?

Thanks

 

[VLFit]

I am replying to my own question that went unanswered. If there is any motor shop out or OEM there that has tested many motors, even just armatures during rewind, with high voltage AC and has some numbers as to the mA of AC current needed at the test kV vs. motor voltage and hp and ... specs, it would help us to get an idea of the power, or mAac current needed to test diffrent sizes to help spcify the AC hipot equipment needed. We can't use DC all the time.

Thank you

 

[Zogzog]

WLFit, why don;t you VLF it? Much smaller power supply needed then, or is that the point you are trying to make?

 

[rasevskii]

For your 12000 HP motor why not just "hipot"it at 220VAC to ground and measure the current in mA. The AC current at the actual HV test voltage will be proportional to the 220VAC current.Just to get an idea. The capacitance of the winding Xc will determine the current at the AC voltage used. This ignores any ohmic leakage, however.

rasevskii

 

[Zogzog]

VA=2*(pi)*f*C*V

So I think what you really need is the capacitance of the motor.

 

[rasevskii]

Capacitive reactance, I should have said...Is this posting to prove the value of VLF testing?

rasevskii

 

[VLFit]

this posting is not to push vlf, i didn't mention it. we work with many EASA motor shops and most do not know the uF rating of the windings they need to test. I am trying to help them. Sure one can hipot at any lower voltage and scale it up, I was just wondering if anyone in the motor world had any kind of matrix designed to cross motor types, sizes, etc against AC hipot needs. I know it is nearly impossible because of the many different geometries, I was just looking for at least a few examples.

 

[electricpete]

See table 4.1 here for estimate of charging current based on motor size (You'll have to guess the system voltage).

http://www.crcnetbase.com/doi/abs/10.1201/9781420015393.ch4

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(2B)+(2B)' ?

 

[VLFit]

thanks electripete but I don't have a subscription to that.