Motor Input Voltage and Rectifier Firing Angle Variation with Load Torque in Constant Current Operated Induction Motors

In current source inverter (CSI) fed induction motors (IM) operated under constant current, the input voltage changes within large limits as the load torque changes. In such an operation the motor mostly operates on the saturated portion of its magnetizing characteristic, and non-linear relation exists between the input voltage and the load torque. Therefore in this paper a numerical technique is presented for obtaining required input voltage corresponding to a given load torque, which can be used for estimating the firing angle of the input rectifier, which in tum can be used for predicting firing angle in terms of load torque. Proposed technique has been demonstrated with an example.