Checking a DC motor

[garzajk]

I was just wondering how you can check to see if a DC motor is bad. I know you can use a Megger on a 3 phase AC motor and other AC motors, but can you use a megger on DC? If not what do you use to check them? I am now working at a plant that uses a lot of DC motors, I am fairly new to these because my last job used mostly 3 ph 480v motors. Any help would be appreciated.

Thanks,
Jeremy

 

[danickstr]

shunt or series?

edit: i think in either case a voltage drop test of AC across the field leads should all be equal. If you have an infrared tester, 140 degrees is normal top end in most cases for motor

 

[billsnuff]

i have worked with reliance equipment over the years, but most of those gray cells retired. Anyway here is a link to reliance maint. and troubleshooting.

http://www.reliance.com/prodserv/motgen/h7000.htm

 

[zog]

You still do a IR test, if >150kW do a PI test, otherwise just a DAR.

Check bolted connections with DLRO.

High pot test per NEMA MG1, section 3.1

You can also do a voltage drop test as danickster mentioned but it is an optional test.

Your DAR/PI should be >1
Your IR at 40 degrees C should be >100M

 

[garzajk]

Thanks I appreciate your help!