effects of insulation test

[emadshaaban]

dear sir
is there any effects of applying insulation resistance test many times for windings?

 

[mikekilroy]

Other than many results? If one test passes, why do it many more times? Or are you asking in respect to your other post of how often, 1M, 6M, etc?

If you do not exceed the devices max voltage ratings then no harmful effects I don't think. If you exceed the max voltage rating of the device (wire, insulation, etc) then it of course can degrade it..... some.... how much? I would venture a guess: not enough to measurably harm it if just a few times in a few months/years. I have seen motors short in as little as 5 minutes from 3x max voltage rating spikes - this experience was loose motor cable connection causing 3000v spikes and there were probably 1000 of these spikes in that time. I will say also the insulation on these motors was not great as they had air pockets in the windings allowing air to ionize from the corona and eat the insulation.

 

[electricpete]

I agree. If appropriate level of dc test voltage is used (IEEE43), test is conducted properly, and test passes, we should expect no adverse effects to the winding. It can be repeated as often as you want (within reason).

IEEE43 specifies "After completion of the test, the winding should be discharged through a suitable resistor, sized to limit the instantaneous current to 1 A". The concern is that a transient from slapping a solid ground could damage the winding (although I can't say I've ever heard of that).


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(2B)+(2B)' ?

 

[emadshaaban]

thank you for you.i have made that question because somebody said to me that D.C insulation test each 6M preventive maintenance can reduce winding insulation time life.than you.