On the Selection of the Number of Poles of Three-Phase Induction Motors for Variable-Speed Power Drive Systems

The selection of the number of poles of three-phase, squirrel-cage induction motors (SCIMs) for a given set of operating points of a variable-speed power drive system is not straightforward. In this chapter, the performance of 2-pole and 4-pole 50-Hz SCIMs for specific torque-speed operating points and optimized sinusoidal supply voltage in terms of frequency and amplitude is compared by means of simulations and experimental tests. For a given target torque, it is shown that the 4-pole SCIM has lower losses and absorbs less current at a target speed of 1500 r/min and the 2-pole SCIM has lower losses at a target speed of 3000 r/min but absorbs more current. The reduction of the motor current leads to lower conduction losses in the variable-speed drive, contributing to the increase of the power drive system efficiency. The conclusions presented in this paper contribute to a better decision regarding the selection of the number of poles and rated power of SCIMs for a given torque-speed range.