Constant-speed solutions applied to the evaluation of induction-motor transient torque peaks

The paper outlines the derivation of a constant-speed transient torque solution for a polyphase induction motor for any switching condition. A representative selection of computed torque/time patterns is given, for a 5hp motor, including all torque components. These are compared with actual experimental results. Also for this motor, the way in which the transient negative torque varies with speed is shown for the speed range zero to three times synchronous speed. For speeds above synchronous value, it has been found necessary to use values of rotor parameters corrected for the skin effect of the speed-frequency transient currents. Simple approximate expressions are given for evaluation of the maximum positive torque peak during starting from test and the maximum negative peak when the supply is connected when the rotor is rotating at some finite speed. The results given by such expressions are compared with values obtained from both computed and recorded torque/time patterns for motors up to 100hp.