System and method for controlling induction motor applicable to electric

Abstract

A system and method for controlling an induction motor which basically achieve reductions in a steady state loss and in a transient loss of the induction motor such as a stepwise input of a torque instruction value T.sub.e *. Basically, a steady-state loss minimization magnetic flux calculating section calculates a secondary (rotor) magnetic flux .phi..sub.r * which minimizes the steady-state loss of the induction motor in response to a torque instruction value. A target magnetic flux .phi..sub.r and a differentiation of the target magnetic flux d.phi..sub.r /dt are thereafter calculated using a low pass filter transfer function such as .phi..sub.r =.phi..sub.r * 1/(1+.tau..sub..phi..S)(, wherein .tau..sub..phi. denotes a time constant, and S denotes a Laplace operator). A target torque T.sub.m is calculates using a predetermined transfer function in response to the torque instruction value such as T.sub.m =T.sub.e *.1/(1+.tau..sub.T.S)(, wherein .tau..sub.T is a time constant for the target torque). At the steady state, the slip frequency .omega..sub.se is set to a loss minimization slip frequency .omega..sub.se-opt and, at the transient state, a magnetic flux response gives an optimum value corresponding to a torque response described above. The induction motor is used to drive an electric motor-driven vehicle.