| 摘要 |
1,267,421. Control of D.C. motors. GULTON INDUSTRIES Inc. 8 April, 1969 [5 April, 1968], No. 17842/69. Heading H2J. In a battery powered vehicle, regenerative braking down to a low speed is facilitated by a voltage boosting circuit 33 connected to the motor 4, and a shunt field 4C is connected, for braking, to the otherwise series-wound motor. The boosting circuit comprises an inductor 35 connected between the positive armature terminal and the battery via a diode 40 and switched periodically by thyristors 43, 44 and 47, 48 with a commutating capacitor 41. The thyristors are fired in alternate pairs by a circuit 45 which comprises a relaxation oscillator and bi-stable circuit (Fig. 3, not shown), the frequency of the oscillator and hence the amount of braking being adjustedby a brake pedal controlled rheostat 26. In an alternative arrangement (Fig. 6, not shown) the average current through the inductor is kept constant for a given pedal setting by an operational amplifier which adjusts the frequency of the oscillator according to the volt-drop across a resistor in series with the inductor. The brake pedal also controls a rheostat 29 in the shunt field circuit and a mechanical brake 22 through a lost-motion link so that it is effective only in the final stage of braking. Change-over from driving to braking is effected by a relay K1 energized by first movement of the brake pedal. The speed of the motor during driving is controlled by a thyristor 6 having a turn off circuit 10 which comprises two pairs of auxiliary thyristors and a commutating capacitor (Fig. 4, not shown) which are fired in alternate pairs by a square-wave generator. Triggering pulses for 6 are produced by a relaxation oscillator and unijunction circuit whose operation is synchronized with the square wave generator, the firing instant and hence pulse width being controlled by an accelerator operated rheostat in the oscillator circuit. Some shunt field current is provided through resistor 5 to prevent runaway on no load. |
