ABSTRACT
Motor power losses refer to the consumption of electrical energy not converted to useful mechanical energy. Motor power losses are important in motor design for anumber of reasons:(1) Power losses in electric motor can substantially increase the temperature rise in the windings and deteriorate the performance characteristics of motor. The vast majority of power losses are converted into heat energy, which must be eventually dissipated from the motor to the surrounding environment. Consequently, it is highly desired to understandthe mechanisms of various power losses for providing the best suitable solution of motor cooling. (2) The motor efŽciency is deŽned as the ratio of the power output (which equals the power input minus the power losses) to the power input. Thus, the higher the power losses, the lower the motor efŽciency. From an economic standpoint, higher power losses are always associated with increased motor costs. (3) The conversion of power losses into heat energy may cause an excessive internal temperature of motor. Thus, power losses have astrong impact on the selection of cooling modes that are required to keep the motor temperature below the maximum allowed value. (4) Temperature is amajor cause of degradationof insulation materials. Excessive motor temperature can accelerate the aging of winding insulations and thus reduce their lifetime. (5) High temperature can signiŽcantly reduce magnetic properties of PMs to lower the performance of PM motors. As the temperaturebecomes higher than the Curie temperature of the magnet, all magnetic properties are eventually lost. (6) High temperature may cause bearing grease to deteriorate, leaving motor bearings without adequate lubrication. (7) Asmall portion of the total power loss may be converted to sound energy, leading to high acoustic noise emitted from the motor.
