Monitoring VFD motor current

[nisqually]

Can anyone give me a few good reasons for monitoring the current on a 5HP motor with VFD? What useful information could be obtained relative to motor condition? We own a Baker Instrument Company Motor Performance Monitor Explorer II Series. Thanks!

 

[electricuwe]

There are some reasons to monitor the current e.g. protection but these issues should be taken care of by the microcontroller of the inverter. If additional information e.g to perform preventive maintainance is required there are some ways to get this information. Search the IEEE Transactions on Industrial Application for information on that topic.

I do not know details about the device from Baker but you should be aware that operation of a motor from an inverter differs significantly from operation from the line. So unless your monitor has not been designed for that kind of duty you will not get useful results. If your monitor is designed for that purpose the manual should explain what information could be obtained.

 

[jbartos]

Suggestion: Essentially, such current monitoring could be viewed as backing up the VFD current monitoring (if available). Considering that the VFD could have about 50000 hours of MTBF, then the motor current monitoring would be more imminent after 10 years of the VFD operation or so. However, if the motor has some peculiar load pattern, it will be prudent to monitor its current, at least for some time.