VFD and shop ventilation

[Ruperto Mendiones]

I am planning to put a roof belt-driven roof ventilator in my being-designed shop. The ventilator can be ordered with a 3 phase 220 v motor [ordinary duty]. I would like to use the vfd to control speed between 40-100% of rated speed. The motor will run continuously for 4+ hours.

Am I risking insulation failures or overheating? Are there other considerations to be addressed?

Does anyone have any experience with running an ordinary 3-phase motor on a vfd for hours at a time?

[Mike Henderson]

Running the motor at, say 40%, is not a problem in and of itself. The problem is whether the motor will be cooled. All motors have some type of fan to cool them and running it slower will cause it to move less air.

But the fact that you're using it in a fan application, and that the power required for a fan increases at some mathematical power (cube???) with speed, I would think that you're going to be find. To be sure, run it at 40% for maybe 30 minutes and then put your hand on the motor to see how hot it is.

Mike