Comparative evaluation of power-factor improvement techniques for squirrel-cage induction motors

Relatively simple methods of improving the power factor of squirrel-cage induction motors were tested. The methods evaluated under controlled laboratory conditions for a 10-hp, high-efficiency motor were terminal voltage reduction, terminal static capacitors, and a floating winding with static capacitors. Each of these techniques was tested over a range of torques from zero-load up to 150% of rating. The effects of the different configurations on starting performance, pull-out torque, and operating efficiency are considered. The test results are compared with mathematical model predictions which then are used to identify optimum conditions for each of the power factor improvement techniques. Finally, the relative economic value and the implications of component failures of the three methods are discussed.<>