Selection and Design of an Inverter-Driven Induction Motor for a Traction Drive System

The considerations and trade-offs involved in the selection and design of an inverter-driven induction motor for a traction drive system are described. The inverter is transistorized and operates in a pulsewidth modulation (PWM) mode in the constant torque region and in a six-step square wave mode in the constant power region. Drive system requirements establish the 50-hp peak motor rating and the motor voltage. The aspects of an induction motor designed to be driven from an inverter are presented. These include the number of poles and rotor bar shape of the motor. Expressions relating the motor performance to motor design parameters are derived. The aspects of the inverter power source are presented. These include the constant volt-ampere characteristics of the inverter and the relationship of motor inductance to the inverter design. A final motor design is reached, Contrary to previous expectations, the best design is a two-pole motor.