Testing resistance with a load - Electrician Talk - Professional Electrical Contractors Forum

EROD · 08-03-2009, 02:22 AM

What would be an acceptable way to get an accurate reading for resistance with voltage applied? Tested from a 208 v motor.

And would readings from the capacitor also be possible?

Thanks.

drsparky · 08-03-2009, 08:13 AM

Use ohms law.

EROD · 08-03-2009, 10:05 AM

I know what the stated resistance is.

I want to test the resistance on the operating motor. I want to see if there is a change in impedance.

This may help. I work on large Printing presses. Certain components are difficult at best to get to.

Zog · 08-03-2009, 10:26 AM

Quote:

Originally Posted by EROD

What would be an acceptable way to get an accurate reading for resistance with voltage applied? Tested from a 208 v motor.

And would readings from the capacitor also be possible?

Thanks.

Resistance of what? The insulation? The windings? Something else?

drsparky · 08-03-2009, 10:28 AM

Check voltage while the motor is running, preferably with a RMS voltmeter, monitor amplitude at the same time. Divide voltage by amplitude. You now will have resistance while the motor is running.
Ohms law R=E/I