Hipot or Megger for 50 kW motor

[Clyde38]

I have been told that for lager motors a Megger test is better than a Hipot test. That is to say, lager motors will fail a Hipot test and not a Megger test (I'm not sure exactly how that makes the Megger test better). I have looked through the posts and could not find anything referencing this.

Clyde Hancock
Design & analysis of electric motors and generators

http://www.motorconsultants.com

 

[waross]

A 480 Volt rated motor will be meggered at 1000 Volts DC.
The same motor will be Hi-Potted at 1960 Volts AC with a peak voltage of 2772 Volts.
The old standard was twice the working voltage plus 1000 Volts. (480V x 2) + 1000V = 1960 Volts.
Meggering is pretty standard at lower voltages (Up to 600 Volts.)
Hi-Potting is not much used anymore.
At higher voltages other more sophisticated tests are generally used.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[panter]

Megger test is not destructive insulation test method but with Hipot test motor should fail .If it is used on an essential motor and without meger test before it may be possible to make a serious technical error .
Good luck

 

[controlsdude]

I would look at the example of a 480v VFD rated voltage peak for 1300vpk to 1600vpk nema rated motors. As you can tell just from a spec on the motor its below the HIPOT voltage. I dont think HIPOT is a peak voltage either?

 

[waross]

Forget the Hi-Pot. Megger the motor at 1000 VDC.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Clyde38]

Thanks to all for your replies.

Clyde Hancock
Design & analysis of electric motors and generators

http://www.motorconsultants.com

 

[edison123]

A megger test indicates the insulation dryness and cleanliness. It does not measure the dielectric strength of the insulation. Only a Hipot will do it.

For mass produced 50 KW motors, one minute Hipot is only a type test. Some OEM's will do a quick flash HV test (which is a quick and dirty method) for all such motors.

Muthu

http://www.edison.co.in

 

[Clyde38]

Thanks Muthu

Clyde Hancock
Design & analysis of electric motors and generators

http://www.motorconsultants.com