VFD - Motor conductors overheating

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bnewport

bnewport

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Indiana
I am troubleshooting a VFD that feeds a 30HP motor approx. 60' from the VFD. The overload relay on the VFD trips occasionally, and the conductors are very hot. The running amps are within nameplate. The VFD, breakers and feeder are sized correctly. The breaker upstream from the VFD has also been tripped in the past. Any ideas?

Bryan
 
How about voltage readings while under load, both the supply to the VFD and at the motor.

For that matter, how about amperage readings, too.
 
Basics

Basics

Check to see the motor and breaker overload settings are correct first. Some breaker manufacturures Insist that it is in the interest of safety that they send them out of the factory at the lowest settings. Pretty funny huh?? Also if the conductors are hot check that all connections are tight.
 
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What size is the wire from the VFD to the motor? , Also, what voltage?

Make sure your clamp-on will read true RMS. If ti doesn't, you'll get lower than actual readings on distorted waveforms, like the output of a VFD. As a quick, but not very accurate high impedance ground fault check, put your clamp-on around all 3 leads. If it reads anything but 0, you have a ground fault somewhere.

If this all looks good, you might have to change the VFD's carrier frequency, especially if this is an older motor.
 
You say the conductors are hot? Since hot is considered a relative term, perhaps you can provide the actual surface temperature of the conductor. Also, what is/was the ambient temperature when it was determined the conductors were "hot".
 
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