PURPOSE: To reliably perform the starting of an induction motor type electric vehicle on an increasing grade by a method wherein the output polarity of a pulse number-voltage converter, which detects the revolution number of an induction motor, is switched when the backward movement of the electric vehicle was detected.
CONSTITUTION: The pulse number-voltage converter 52 generates the voltage in proportion to the pulse frequency outputted from a pulse generator 51. An electric vehicle backward movement detector 61 gives a signal to a polarity switching device 62 when the electric vehicle begins to make a backward movement and switches the output polarity of the pulse number-voltage converter 52. An adder 53 adds up a slip frequency command value fSP and the revolution frequency fR of an induction motor 3, and outputs the frequency command fE of an inverter 2. At a current controlling device 42, the current IM of the motor is compared with the command value IP, and the output voltage of the inverter 2 is controlled. Through these procedures, the starting of the vehicle at an increasing grade can be performed reliably.
OKAMATSU SHIGETOSHI
JINBO YOSHIJI
IBAMOTO MASAHIKO
