Here’s an essential truism – knowing what to ask for is key to getting what you want. What follows is a checklist, with comments as appropriate, intended to help you define your variable speed drive (VSD) needs and ensure you get exactly the drive your application requires.
- Full load amperage (from the motor nameplate)
This will typically be labelled as “F.L.A.” on AC induction motors; “ARM Amps” and “FLD Amps” on DC motors. Rated amperage, NOT horsepower, is used to properly size VSD’s, because the power electronics are sized to conduct a certain amount of current for a certain amount of time, which can vary for a given motor horsepower depending on torque required.
- Rated phase, frequency and voltage
This information can again be found on the motor nameplate. Often AC motors are rated for dual frequency (50/60 Hz); if so, this information should be included on the nameplate. If you intend to operate such a motor above rated speed, take care to note any changes to Service Factor; the dual frequency rating usually means a lower Service Factor when supplied […]