ANLAGE ZUM STEUERN EINES ELEKTRISCHEN GLEICHSTROM-FAHRMOTORS

摘要

Apparatus for increasing the available regenerative braking energy and for enabling low current control without frequency variation in a time-ratio controlled main thyristor power circuit for a direct current traction motor. A variable impedance element is serially inserted in a motor armature free-wheeling current path between a free-wheeling diode and the motor armature, the variable impedance element preferably comprising a power resistor and parallel connected thyristor. During electrical regenerative braking the thyristor is used to modulate the power resistor to thereby present a continuously variable impedance in the armature current path. During motoring at very low speeds the thyristor can be operated to modulate the power resistor and thus reduce the minimum controllable level of motor current normally limited to commutation current level without the necessity of reducing the main thyristor operating frequency. The thyristor is gated on by conventional means but is gated off by triggering the commutation circuit of the main thyristor, thus eliminating the need for a separate commutating circuit for the thyristor.