Supplying MV Motors From LV Adjustable-Speed Drives

In some cases where a medium-voltage (MV) motor is to be used in an adjustable-speed application, the system design, equipment availability, or other factors might favor supplying the motor from a low-voltage system by way of a step-up transformer. While simple in concept, the use of a transformer to step up the drive output voltage to MV level is not a common practice. This paper discusses the characteristics of the drive, transformer, and load that affect system performance. Using a case study for a pump application, this paper develops a method using voltage drop and starting torque calculations to analyze the system.