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Oversized VFD

Oversized VFD

Oversized VFD

(OP)
Are there any problems associated with using a large VFD on a much smaller load (200 hp VFD and 100 hp motor)

RE: Oversized VFD

No. A 2:1 ratio is not considered a problem in any aspect - except price.

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: Oversized VFD

Most VFD's allow the motor details to be input to the VFD via parameters. It is important to do this especially when a smaller motor is being used to ensure the VFD provides the necessary current limit protection, IsqT protection (if no external thermal protection is used) as well as ensuring any internal motor modelling for performance sake is correctly set up.

RE: Oversized VFD

You shouldn't have a problem in your case, but some VFD´s overload protection can only be reduced to a certain fraction of the drive's rated output current.  For example, I think the Saftonics GP10 overload funtion only works with motors rated at least 20% of the drive's rating, so for example a 5 HP motor would be unprotected on a 50 HP GP10 drive, and you would require external OL protection.

RE: Oversized VFD

You might want to set the overcurrent limit or torque limit down in Group 20 as the factory defaults will really bury the motor in overload.  In some applications that is done deliberately but in many other situations you just might get more torque than you bargained for and machine damage could result.

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