Operating 3 phase motor above frequency

[AGCB97]

I have a question about operating a 3 phase motor at a higher frequency that its placard frequency.

I am running a 1 1/2 HP motor from a VFD. Is it possible/wise to run it at a higher speed by increasing the frequency output of the VFD? It mostly runs at low load. I have seen that others do this. What ramifications might this pose?

This is the motor placard.


Thanks
Aaron

 

[Technical Ted]

One consideration is "what is the speed the system designed for". Both for the motor and whatever you are driving. Motor bearings and type (ball vs bronze, etc.) have a max. recommended speed. Also, whatever you are driving with the overspeed motor has RPM limitations as well.

I think I read on-line someplace the "standard" recommendation for a motor for this, but I don't remember where. You could try Googling it and see what comes up. You might even try contacting the motor manufacturer. That motor nameplate shows a little slower RPM than most standard 3 phase motors right out of the gate.

Ted

 

[machPete99]

For 1800 RPM motors you can typically run up to double speed (120 Hz), as they often share the same bearing configurations as their 3600 RPM counterparts. Over that may be pushing things.

If it is an older/used motor you might want to refresh the bearings with quality name brand items. For even higher speed operation you can try to find non-contact rubber sealed bearings which are rated for higher RPMs.

 

[AGCB97]

Thanks for the replies. I'm going to try a 25% increase and see how it goes.
Aaron

 

[JimDawson]

Most standard small (<5hp) 3 phase motors are perfectly happy running between 30 and 120 Hz. The 4 pole motor you have there would be perfectly happy at 120Hz (3600 RPM).

If the rest of your machine will take the higher speed, then no problems.

 

[AGCB97]

Thanks

 

[Dabbler]

Going at 25% over speed is a fine step. See how much heat build up you get in the bearings and how smooth it it runs over an expected length of ti e (30 minutes?) - your armature might not be as well balanced as the next one. You can increase in steps until you feel it is near maximum.

The probable maximum is 120 Hz as has been stated above. I wouldn't run it at anything above that.