Comparison and detection of abnormal conditions in induction motors

Deficiencies like unbalanced voltages or harmonics in the voltage source could result in problems like excessive losses, over-voltages, mechanical oscillations, and interference with control electronics. Detecting these abnormal conditions in the machine is of great importance in the interaction of the electrical machine and the power grid. In this paper the effect of the unbalanced voltages, harmonics and flicker on the motor performance, have been investigated. Then, monitoring these unhealthy condition using electrical machine parameters is carried out. In this case, motor itself can act as the sensor that detects abnormal conditions. Also this paper investigates the negative effects of unbalanced sinusoidal voltage which always present in the power supply over balanced (inverter supply) non-sinusoidal voltage on the performance of induction motor in terms of line currents, power factor and efficiency. According to the test results and analysis, the negative effects of unbalanced sinusoidal voltage are more than the balanced no sinusoidal voltage on the motor´s performance.