VFD For 2 Speed Motor

[sdt1104]

This may be an echo of whats been said. Frequency drive motors should have ball bearings. You need a motor designed for inverter use. We have over 300 VFD motors 25 to 100 HP and we set the minimum speed at 20Hz or off. You can expect some fluting on the motor bearings; that is a static build up that discharges at the motor bearings causing premature failure. We tried the "AGIES" grounding rings with little or no success. On the up side, we have gotten really good at changing motor bearings. Using the existing motors, you will most likely get to sell them the correct motors in a few months anyway.

[The Reaper]

Thanks for all the help everyone. The customer doesn't want to take any chances and will be buying new motors.

[EEAllen]

yes, you can just put the motors on their high speed, and use the VFD on the power supply

[wcsmith]

I have never heard of a low RPM bearing requirement on a cooling tower shaft; however, if the tower has a gear reducer low RPM's can affect bearing lubrication and an oil pump may be required to operate using a VFD at low RPM's.