Transient torques in induction motors, due to switching of the supply

An experimental study of transient torques in induction motors, due to application of the supply, is described. The transient-torque recordings were obtained by means of a 2-phase induction generator, used as an accelerometer, and apply to the free-rotor, i.e. unloaded, condition. Point-on-wave switching was used to obtain selective transient-torque patterns. Results are given for 3-phase and single-phase motors. In the former case, the effects of nonsimultaneous switching, and of connecting the motor to the supply while the rotor is still rotating, are shown. The results confirm the assumption that the transient torques are due mainly to the interaction between transient asymmetrical flux and alternating currents.