Selecting the proper motor drive is a process that begins at the load. We must first determine if your motor type / application is compatible for use with single phase output VFDs. Not all single phase induction motors are compatible for use with single phase output VFDs.

Single Phase Output VFDs are designed for use with single phase “Shaded Pole” and “Permanent Split Capacitor” (PSC) type motors. These types of single phase motors have ratings in the sub-fractional to fractional horsepower range (1/20 – 1.5HP). Additionally, because of their low starting torque characteristics they are most often used on direct drive fans, blowers, and pumps. Conversely, they are NOT used on belt driven or hard to start loads such as compressors, conveyors, or high head pressure pumps.

Single Phase Output VFDs are NOT compatible with “Switched-Cap” (Capacitor-Start or Capacitor-Start/Capacitor-Run) or “Split Phase” type single phase AC induction motors. (Why?) Single Phase Output VFDs are also NOT intended for operation with electrically commutated, or non-commutated “Brushless” (BLDC / BLAC) or other single phase special designs such as “Switch-Reluctance” type single phase motors.

The use of a single phase “PSC” or “Shaded Pole” type motor for high starting torque applications should be avoided. (Why?) This rule applies in general whether using a VFD or not. The VFD should not be viewed as a means of compensating for the inherent limitations of low-torque motors. Examples of VFD applications to avoid with single phase Shaded Pole or PSC motors include belt/pulley loads, compressors and pumps with high head pressures and heavily loaded conveyors. Expect to over-rate a single phase drive to meet high starting currents if a single phase drive must be used for a high-torque application.

*Always contact us here at Anacon Systems for assistance determining your motor’s compatibility with single phase output VFDs. You will want to have your motor’s nameplate data available to assist with this.