Analysis of electromagnetic torque of induction machines with the load torque changes suddenly

Since many Cascaded H-bridge multilevel (CHBML) inverters that are applied to drive high voltage machines can´t transmit electric energy reversely, the electric energy transmitted from the machines may damage the inverters. This paper presents a transfer function to analyze the electromagnetic torque, when the load torque changes suddenly. Based on the achievements, the electric energy that flows between the machine and the inverter can be calculated. And then, a method is proposed to prevent the reversion of the direction of energy flow. Furthermore, the transfer function can be used to guide the design of the control system of induction machine. Simulation results verify the transfer function and the presented method.