Abstract: There are provided a first chopper CH1 connected in parallel with armatures M1, M2 of main motors of an electric vehicle and operating during a braking mode, and a second chopper CH2 connected in series with the armatures and operating during a powering mode. Both the choppers have a reverse-directional conductivity. A third chopper FCH is further provided to control a field current of the main motors. According to this invention, an arrangement of a main circuit of the electric vehicle is not necessary to be switched over, even though the operation mode thereof is changed. Further, compared with the prior art, the number of the choppers used decreases, so that an economical control apparatus for the electric vehicle can be realized.

Abstract: A control apparatus for an induction motor comprises a variable voltage, variable frequency inverter feeding the motor, which is controlled by the PWM control. A secondary current component and an exciting current component of the motor are obtained by the calculation on the basis of a motor current and an actual slip frequency of the motor. From the thus obtained secondary current component, an actual torque produced by the motor is calculated. A frequency reference for the PWM control is obtained by the comparison result of the actual torque and a torque reference. A modulation factor reference for the PWM control is obtained by the comparison of the exciting current component and an exciting current reference. According to this control apparatus, the torque of the induction motor can be controlled to follow the torque reference with a high accuracy.