Variable speed drives evaluation test

We present a test protocol and results of tests on pulse width modulated (PWM) drives rated at 3 hp and 20 hp and supplied from a 480 V line. The induction motor was turning a 25 hp computer-controlled DC dynamometer. This dynamometer was powered from the same source through a stepdown transformer and a regenerative controlled rectifier. Data (speed, torque, input voltages, currents) were collected and processed in a data acquisition system. The following tests were performed: efficiency and harmonics, voltage sags, and capacitor switching transients. Tests wee also conducted on three nontypical drive configurations.