Determining constant power speed ratio of the induction motor from equivalent circuit parameters

The equivalent circuit of the induction machine is used to derive analytic expressions for the constant power speed ratio (CPSR) of an induction motor traction drive. The formulas indicate that while many model parameters influence the CPSR to some extent, it is the maximum permissible magnetizing current magnitude, dc supply voltage, base speed and torque requirement, and leakage inductances that have the greatest effect. In situations where the motor design is fixed the only parameters that can be varied by the drive designer are the DC supply voltage and power rating. For such cases explicit formulas are developed to find the supply voltage and power rating that meets a given CPSR requirement.