On-site efficiency evaluation of three-phase induction motors using synthetic loading methods

Determining the cost-benefit analysis of replacing existing equipment with energy efficient machines is a challenge, especially since the testing of existing machines to determine their efficiency typically requires removal from site and testing at an approved laboratory, hence diminishing the economic savings that can be achieved. This paper presents a novel method of evaluating the efficiency of three-phase induction motors in situation. Synthetic loading electrically convinces the test motor to draw full load current at rated voltage. The machine operates at or near full load speed and at rated temperature. Therefore, all the losses will be present during the test. Simulated results based on measured parameters show that the total losses can be identified by measuring the voltage and current input to the motor undergoing synthetic loading. Hence, since the rated input power and the total rated losses are known, the efficiency of that machine can be determined.