Application of a Squirrel Cage Induction Machine as a Dynamometer for Motor Heat-run Tests

The paper documents the application of a three- phase induction machine as a dynamometer in a three-phase motor testing experiment, wherein the motor is required to be fully loaded. Two similarly sized induction machines were used for the experiment, with the output power of the induction motor matching the required input mechanical power of an induction generator. Two low-cost methods of achieving a dynamometer load were tested. One method was through using a self-excited induction generator (SEIG) setup with an electrical load made of commercial heater strips. The capacitance providing the excitation was estimated using theoretical calculations, but it was found to be insufficient for fully loading the SEIG. The second method was by supplying both machines with low-cost variable frequency drives (VFDs) with one VFD operating in regenerative braking mode with braking resistors to provide the necessary dynamometeric load to the other machine. It was found that the motor loading could be controlled by adjusting the supply frequency of one machine relative to the other machine. However, some complications arose with preventing inadvertent overloads and tripping which will be discussed.