SUPPLY INSTABILITY INDUCED TORQUE VARIATIONS OF A THREE PHASE ASYNCHRONOUS MOTOR

The torque profile of a three phase asynchronous or induction motor is an indicator of the load handling capacity of the motor. The torque profile of the asynchronous motor is determined by the motor design and by the nature of the voltage supply. The power supply network in Nigeria is unreliable with frequent supply interruptions and outages daily, due to insufficient power generation and supply capacity. These disturbances and recurrent switching on and off may trigger voltage swings below and above the rated line voltage coupled with the tendency for supply frequency variations. In this study, the torque profile of a typical three phase asynchronous motor running under simulated power supply variations is studied in order to reveal the effects of such fluctuations on the motor. Power supply variations, interruptions and low power quality impair motor performance characteristics and these affects the reliability and operational efficiencies of processes where such motors are installed. The result reveals torque variations from the rated value with changing supply conditions which is undesired for a smooth industrial operation.