Improved efficiency test methods for three-phase induction machines

The results in this paper demonstrate that the synthetic loading methods described are able to be used to evaluate the efficiency of three-phase induction machines. Synthetic loading causes the machine, as it is rotating, to periodically accelerate and decelerate. This causes the machine to draw, on average, rated current, at rated voltage at or near rated speed, thus producing rated losses. The total losses for efficiency evaluation are identified by taking the average of the measured input power over each synthetic loading cycle. The measured results give excellent agreement with the conventional full-load efficiency test method. The synthetic loading test methods are portable with no loss of accuracy, so they are suitable for either on-site or laboratory use. The test is easy to set up, requiring only that the motor be decoupled from the load and electrically connected to an inverter controlled from a PC that also displays the results in real time. The efficiency evaluation method proposed is accurate, easy to use and considerably reduces the testing time compared with conventional methods, hence reducing testing costs.