An Accurate Mechanical Overload Detection for Induction Motor via Sensorless Load Torque Estimation

Induction motors are widely used in many industries. In many cases, the load torque value on the motor shaft is variable and the measurement of the torque allows control of the technological process. This paper proposes a torque detection method that can be implemented without expensive sensors and very accurate model of the induction motor. To implement this method only stator current measurement is required. Motor speed is detected and calculated from current spectrum. After that, the torque can be estimated from linearized torque-slip relationship. Proposed method is explained theoretically and followed by experimental implementation results. The test results validate the proposed method and show close agreement between estimated speed and torque values and the real measurements.