Numerous methods exist for measuring the efficiency of motors

but many of them require shutdown

and need disconnection of the motors from loads for a no-load test

which have high cost and large effects on production.A new measurement method is proposed for in-situ large power motor efficiency without shutdown and no-load test.It uses a measuring instrument to measure input voltages

input power

power factor and rotating speed.An equivalent circuit model are calculated by using the genetic algorithm and the motor efficiency is got.Actual test results show that this method is approximate to torque-gauge method

so it confirms the validity of this method.