Hipot leakage current

[Brad1979]

Does anybody know of any standards for specifying maximum leakage current during end of line hipot tests? This would be for low voltage motors (460V or less). UL 1004 specifies a hi-pot voltage but not the leakage current. Perhaps there is an IEEE standard?

 

[Zogzog]

You typically will not see a leakage current spec because so many factors determine the leakage, DC hipot tests are typically go-no-go tests.

 

[electricpete]

I agree, no leakage current spec for ac or dc (although you want monitor current during the test to make sure you stay below the test set trip setting.. trip of test set during test can itself create damaging transient voltages).

For ac, there is not even diagnostic value to measuring current (unless you also get a phase angle). That is because there is high capacitive current that overwhelms any true leakage current.

For dc, there can be some diagnostic value to plotting leakage current vs voltage which voltage is increased in a particular step or ramp fashion. See IEEE95.

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[Brad1979]

I'm wondering about AC hi-pot. The hi-pot testers I've seen all have a setting for max leakage current. Is this not a true leakage current? Does it include the capacitive current that electricpete mentioned? What is the purpose of setting the max leakage current on a hi-pot tester if hi-pot tests are basically go-no-go?

 

[electricpete]

The hi-pot testers I've seen all have a setting for max leakage current.....Does it include the capacitive current that electricpete mentioned?

Yes.

What is the purpose of setting the max leakage current on a hi-pot tester if hi-pot tests are basically go-no-go?

There is a selector for the meter display range.

There may possibly be an adjustment for the test set overcurrent trip point lower than the max level required to protect the test set.


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[electricpete]

Here is an example which matches the types of controls I mentioned. Others may vary.

http://www.phenixtech.com/9-ACDportables.asp

Multi Range current meters ....
Adjustable overcurrent trip from 10% to 110% of rating ...

One point you should believe: the results of a ac hi-pot test with corrrect hi-pot machine settings (*) should not depend upon the settings of the hi-pot as long as voltage is at specified level. * In other words, don't set the trip so low that it will trip for a normal motor. Once the ac starts to increase above the normal capacitive current for the motor, it will surely increase rapidly to the trip point, regardless of the trip point.


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