Automatic IM parameter measurement under sensorless field-oriented control

A novel approach to automatic induction motor (IM) parameter measurement under sensorless field-oriented control (FOC) is presented. Before startup, the inverter drive automatically performs the DC test, the no-load test and the locked-rotor test for the driven IM. The only measured values are input current signals. No additional hardware is required in this approach. In order to automatically measure the IM parameters under FOC structure, the concepts of no-load test and DC test should be modified. In addition, because the conventional locked-rotor test requires that the rotor shaft be locked mechanically, this makes automatic measurement impossible. In order to solve this problem, a locked-rotor test at single-phase excitation for sensorless FOC structure is also performed in this paper to facilitate automatic IM parameter measurement. Finally, the test data are then computed to get the IM parameters and the field current command for FOC. The presented method has been tested on a 3-hp inverter-driven IM system. Its effectiveness is illustrated by experimental recordings.