Single-phase capacitor motor efficiency improvement by means of voltage control

The need for higher levels of AC motor efficiency is increasing significantly. Numerous opportunities are available to reach these levels, many of which are being influenced by industry standards and the energy cost. The purpose of this paper is to present a comprehensive study on the optimization of the energy consumption of induction motors through a power factor control system. Indeed, minimum input power and maximum efficiency occur at a characteristic optimum power factor value which can be calculated for any induction motor. Efficiency is shown to be independent of output power when the variable voltage controller reduces the voltage approximately as the square root of the load torque to maintain the required power factor during part load operation. Experimental results, in the case of a single-phase capacitor motor, have demonstrated that the use of such a type of system has a significant energy conservation potential