JPS55117488A - Controlling device for dc shunt motor - Google Patents

Abstract

PURPOSE:To widen a field controlling range by connecting, in a case where an instruction for applying the strongest magnetic field to an electric motor is given when the motor is driven with a weak magnetic field, a field winding to a power source directly at the completion of a regenerative braking operation, which is conducted while the motor is in a regenerative condition, whereby the strongest magnetic field can be applied to the motor. CONSTITUTION:In order to subject an electric motor to a regenerative braking with a field current instruction signal V6 adapted to a larger field current, by operating an operation instruction generator 7, in a case where a field current is set to if with the motor rotated at a speed N1, the field current increases to cause a back electromotive force of an armature 2 to increase. When the back electromotive force has exceeded the voltage of a storage battery 1, an armature current Ia flows in the negative direction so that an armature inversion signal V10, an input into a current comparator 35, becomes positive. The comparator 35 receives as a negative input a reference current signal V20 of a constant level from a reference current signal generator 34. When the inversion signal V10 has become greater than the reference signal V20, a signal V21, which is proportional to the difference between the signal V10, V20, is output from the comparator 35. This signal V21 is sent to a subtractor 36 as a negative input.