Comparative costs of energy losses in induction motors

Techniques are available for reducing energy losses in induction motors that are subjected to variable loading. To examine whether these are cost effective it is necessary to take realistic duty cycles for the motors, true performance characteristics and appropriate costs for power and energy losses in the motor and the immediate electricity supply network. A method of analysis is described and evaluated for a 3 kW 4-pole induction motor. The present value of losses is calculated for a typical operating life and various alternative duty cycles for three performance characteristics. These are for a standard motor, a high-efficiency motor and a standard motor supplied through a power factor controller. The present values of the power and energy savings achieved when using the alternatives to the standard motor are shown to be substantial for duty cycles typical of several applications.