Oversized VFD

[howeng]

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

 

[dinkelja]

No, except cost. Size the VFD to the motor based on the current requirement during peak torque demands. Do not just select drive based on the motor nameplate HP / FLA and the drive rated Hp range / rating.

 

[winnie]

I believe that the oversized VFD will require a feeder that is matched to the VFD, rather than a feeder matched to the motor. This means a more expensive feeder in addition to the more expensive VFD.

-Jon

 

[bsh]

Just make sure the parameters of the VFD will allow the use of the motor in question.

 

[dinkelja]

correct winnie, NEC 430.122(A), the conductors suppling a VFD are required to be sized at 125% of the rated input of the drive.

 

[boater bill]

If you going to use the VFD as the motor protection, make sure you program the motor FLA and not use the default.

What is the application?

I have installed very oversized drives on overhauling loads such as mining conveyors so the drive doesn't trip on a bus overvoltage fault. The motor load suddenly goes to generator load as the the loaded conveyor overcomes gravity or something else equally important.

Hope that helps and good luck

 

[Jraef]

If you going to use the VFD as the motor protection, make sure you program the motor FLA and not use the default. ...

Actually, one should NEVER rely upon the default settings for overload. Always enter as much of the motor nameplate information as you can.

I acknowledge though that lots of people don't bother, it's just that I wanted to point out that they should.