VFD/Motor horsepower mismatch

[minerman]

I had a question today that I'm not entirely sure about... Someone is having VFD problems and wanted to know if its a problem that the VFD is rated 7.5HP and driving a 10HP 480v 3ph ac motor.

It seems like it could be a problem, but I was not sure. I would size a VFD based on the FLA of the motor, so maybe selecting a 7.5HP VFD could be ok. My question is, what exactly does the motor horsepower rating determine? I think its possible that a 7.5HP rated VFD would not be set up to supply enough current for a 10HP motor, so that could be a problem, but you'd have to look at the VFD specifics. Am I correct?

Thanks!

 

[petersonra]

As long as the VFD is not tripping on overcurrent, it is probably OK.


What kind of problems are you having?

 

[weressl]

I had a question today that I'm not entirely sure about... Someone is having VFD problems and wanted to know if its a problem that the VFD is rated 7.5HP and driving a 10HP 480v 3ph ac motor.

It seems like it could be a problem, but I was not sure. I would size a VFD based on the FLA of the motor, so maybe selecting a 7.5HP VFD could be ok. My question is, what exactly does the motor horsepower rating determine? I think its possible that a 7.5HP rated VFD would not be set up to supply enough current for a 10HP motor, so that could be a problem, but you'd have to look at the VFD specifics. Am I correct?

Thanks!

Based on motor efficiency motors of the same HP and speed come with different FLA values. If the nameplate FLA exceeds the rated output of the drive you can run the motor, but may not be at full nameplate speed. Depends on the specific drive there are several programing parameters you need to set within the motor nameplate limits, such as max current, frequency and/or speed. More important though is that your motor is inverter rated. The drive's smarts will either help you or hinder you in accomplishing this during the motor 'characterization' step in the initial startup phase.

 

[weressl]

I had a question today that I'm not entirely sure about... Someone is having VFD problems and wanted to know if its a problem that the VFD is rated 7.5HP and driving a 10HP 480v 3ph ac motor.<br>
<br>
It seems like it could be a problem, but I was not sure. I would size a VFD based on the FLA of the motor, so maybe selecting a 7.5HP VFD could be ok. My question is, what exactly does the motor horsepower rating determine? I think its possible that a 7.5HP rated VFD would not be set up to supply enough current for a 10HP motor, so that could be a problem, but you'd have to look at the VFD specifics. Am I correct?<br>
<br>
Thanks!

<br><br>

Based on motor efficiency motors of the same HP and speed come with different FLA values. If the nameplate FLA exceeds the rated output of the drive you can run the motor, but may not be at full nameplate speed. Depends on the specific drive there are several programing parameters you need to set within the motor nameplate limits, such as max current, frequency and/or speed. Equally important though is that your motor is inverter rated. The drive's smarts will either help you or hinder you in accomplishing this during the motor 'characterization' step in the initial startup phase.