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A chopper and a series circuit of a dynamic braking resistor and a thyristor are connected in parallel with a d.c. motor which is operated as a generator during braking operation. A series circuit of a diode and an inductance element is connected in series with the d.c. motor. A condenser connected

A chopper and a series circuit of a dynamic braking resistor and a thyristor are connected in parallel with a d.c. motor which is operated as a generator during braking operation. A series circuit of a diode and an inductance element is connected in series with the d.c. motor. A condenser connected between the ground and the junction of the inductance element and the diode forms a filter circuit together with the inductance element. Current generated by the d.c. motor flows into a d.c. source through the diode and the inductance element during regenerative braking operation. An over-voltage detector fires the braking thyristor when the voltage across the condenser becomes greater than a predetermined limit value, as a result the dynamic braking operation is performed. A chopper controller varies the interval between an ON pulse to turn the chopper into ON state and an OFF pulse to turn the chopper into OFF state for adjusting ON time and OFF time of the chopper in response to the current through the d.c. motor. An operation changer provides a signal to an automatic phase shifter to extend the interval between the ON and OFF pulses to a predetermined period of time enough to quench the braking thyristor when the braking operation of said d.c. motor is changed from the dynamic braking operation to the regenerative braking operation.

대표청구항 ▼

A braking control system selectively operable in dynamic braking and regenerative braking operation for an electric car comprising: a d.c. motor for driving the electric car; a chopping circuit connected in parallel with said d.c. motor to control a current flowing through said d.c. motor operated a

A braking control system selectively operable in dynamic braking and regenerative braking operation for an electric car comprising: a d.c. motor for driving the electric car; a chopping circuit connected in parallel with said d.c. motor to control a current flowing through said d.c. motor operated as a generator during braking operation; a diode connected between said d.c. motor and a d.c. source so as to permit the current to flow from said d.c. motor to the d.c. source therethrough during regenerative braking operation; a dynamic braking circuit including a braking resistor in series with a braking thyristor fired during dynamic braking operation, and coupled in parallel with said d.c. motor; a pulse generating circuit for providing a first pulse to turn said chopping circuit into ON state and a second pulse to turn said chopping circuit into OFF state; a chopper controlling circuit for varying the interval between the first and second pulses of said pulse generating circuit to adjust ON time and OFF time of said chopping circuit in response to the current of said d.c. motor; a change responsive means for controlling said pulse generating circuit to extend the ON time of said chopping circuit to a predetermined period of time enough to quench the braking thyristor when the braking operation of said d.c. motor is changed from the dynamic braking operation to the regenerative braking operation.