Testing Motor Insulation Resistance

[Nuts&Volts]

Hey guys, I'm looking at picking up a used induction motor that runs on 115Vdc bus voltage normally. I am trying to figure out the best way to test the strength of the insulation before I try to step up the voltage on the motor. It can be run at higher speeds so I'm not worried there.

What ways are there to test insulation resistance. Do I need fancy equipment or can I just use some standard electronics lab equipment? I have access to my college's electronics lab and other research centers if things are needed. I'm going to ask some of my EE buddies as well, but I figured some of guys would know some good tricks to try out.

Thanks
Kyle

 

[jonescg]

I think the standard appliance testers used by test-and-tag guys do insulation testing? There's bound to be a few around your department, and they are surely set up to do isolation/insulation testing.

 

[Nuts&Volts]

Yep, just emailed a buddy and he said our Battery guy at our Center for Automotive Research has a Fluke Insulation Tester. I guess it's that easy haha.

Still interested to know if there are any good ways to do it without owning/having access to expensive equipment.

 

[The Apprentice]

The tool you need is a "Megger" or more properly an insulation tester. These can be found quite cheaply often as part of a multimeter or as an individual meter. Look on e-bay, they usually test at 500v and 1000v and give a readout in Mohms. For everyday use a reading of greater than 1Mohm is useable, but good insulation will read off the scale at over 200 Mohm. It is good practice to isolate the item you are testing from any electronic controls, as 1000v can be damaging to electronic components!

Cheers
Giles.

 

[Nuts&Volts]

Thanks Giles. I'll research that device and check some of the other meters we have sitting around CAR.

Good call on disconnecting the electronics in this case it's only the motor so nothing will be connect to it.