Abstract: An arrangement for preventing inductive interference in an electric car having a power receiver for receiving DC power from a feeder line connected to a DC power supply, an inverter connected between the power receiver and a ground side terminal connected to a rail via a wheel for converting the DC power fed from the power supply into AC power, and a motor driven by the output of the inverter, the arrangement being adapted to prevent a high-frequency signal current transmitted from and/or to a signal station from being affected by inductive interference due to switching currents of the inverter flowing from switching elements of the inverter to a return line by way of a capacitance between a frame and a stator winding of the motor.

Abstract: In a PWM-controlled, variable voltage/variable frequency inverter, a pulse mode, which is identified by a number of voltage pulses within one cycle of an output AC voltage of the inverter, is changed in accordance with a frequency of the output AC voltage and an output AC voltage factor, which is a ratio of an output AC voltage to be produced by the inverter at that time to a maximum value of the output AC voltage which can be produced under a then-present value of a voltage of a DC voltage source for the inverter.

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.

Abstract: The DC power supply current-collected on the electric car is connected with a series circuit of the armature of a driving DC motor and an armature current control chopper and with a series circuit of a field winding and a field current control chopper.Both choppers are controlled so that the armature current and field current are maintained constant until the flow rate of the armature chopper reaches the maximum after starting of electric car. In this period of time, the chopping frequency of the armature chopper is higher than that of the field chopper.When the flow rate of the armature chopper reaches the maximum, the chopping frequency of the armature chopper is made coincident with that of the field chopper. At the same time, the field chopper is switched to the control operation by which the field current is decreased in order that the decrease of the armature current is restricted.