Influence of subharmonics on thermal loads of an induction machine

One of most important energy receivers is an induction cage machine. It can work properly provided that it is supplied with balanced, sinusoidal voltage of appropriate frequency and rms value. Presence of any power quality disturbances leads to additional power losses and to an increase in windings temperature. Higher temperature of windings means faster aging of insulation system. Consequently, power disturbances may cause premature destruction of a machine. One of power quality disturbances that may result in machine overheating, are subharmonics. Their thermal impact on an induction cage machine was usually investigated with simulation method that has been not verified in the previous works. In this paper results of thermal calculations were compared with results of measurements. It was pointed out that the method used in previous works for calculations of thermal impact of subharmonics, causes underestimation of windings temperature