Motor Testing with Different Hz 3

[KllrWolf]

We are building an 80V 3 phase squirrel cage motor to operate at 79 Hz. Our problem comes when testing the motor, we have no power source to test it at the rated speed. If I keep a constant V/Hz ratio and run it at 60 Hz, do I use the torque at the test points and convert the recorded Hp to the Hp the motor will generate at speed? What other issues can I run into doing this. Of course, if someone has a better method, I would be glad to hear it.

 

[waross]

Buy a VFD and program it for 80 Volts, 79 Hz.

Bill
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"Why not the best?"
Jimmy Carter

 

[electricpete]

It comes down to what is the purpose of the testing, who’s buying the motor, and what will they accept (do they want test data, will they accept calcualted data, will they accept test data with calculation included).

I believe the corrections are fairly straightforward at low slip, but very dubious at high slip where deep bar effect kicks in.


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(2B)+(2B)' ?

 

[electricpete]

Actually I was just referring to torque corrections. Loss corrections seem trickier from my recollection.

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(2B)+(2B)' ?

 

[TheBlacksmith]

The increased frequency (nearly 33% more) may also show up in heating that could result in unacceptable temperatures in a marginal insulation system.

 

[KllrWolf]

Thanks for the responses.

waross: I wish, but this is a special on off motor that we are not expecting to duplicate.

TheBlacksmith: The heating concern of the higher frequency was addressed during the design phase and the testing will just be a short dyno performance to make the motor is operating as expected.

electricpete: The customer will accept any calculations required due to equipment limitations. Loss calculations is something I expected to cause problem. What would you consider as high slip as we are only expecting about 5-6% slip?

 

[KllrWolf]

Thanks for all your help. I was able to convince The Powers That Be that we cannot get an accurate test without a VFD.