The effects of nonideal voltage and winding conditions on the performance of induction motors

This paper investigates the effects of over-voltage, under voltage, unbalan ced voltage, and unbalanced windings on the performance of induction machin es in terms of line currents: power factors, and efficiencies A set of thre e motors of 50 hpl 100 hp, and 300 hp, respectively, has been tested. OS th ese. the 100-hp, 4-pole motor was specially prepared by connections that en able either regular balanced-phase windings or unbalanced windings by the r emoval of one coil per phase, The performance (i.e., phase currents, power factor, and efficiency for balanced operation over a range of loads from D to 150% of rated) was established. This was compared to the performance at three different voltage conditions: 10% overvoltage, 10% undervoltage, and 2.5% voltage unbalance. This entire range of commonly encountered, nonideal voltage conditions was then repeated with the 100-hp motor with the windin gs deliberately unbalanced. The test results how the different motors behav e similarly in terms of line current and power factor and differently in. t erms of efficiency when subject to the particular voltage conditions.