| 摘要 |
<p>1,177,775. Control of D.C. motors. HAM MANT & MORGAN Ltd. 12 Aug., 1968 [10 Aug., 1967], No. 36866/67. Heading H2J. To ensure reliability of operation of a D.C. motor at low speeds pulses are superimposed on the output supply 4 to the motor (not shown), the control system comprising a rectifier arrangement R from which a substantially direct current is taken between points 1, 2, to supply the motor through the collector-emitter path of a transistor VT1, a potential divider RV1 across points 1, 2 providing the speed control, and a unidirectional pulsating current from the point 3 being supplied to the base of the transistor. A second transistor VT2 acts as an amplifier, the base of VT1 being connected to the supply 2 via the collector-emitter path of VT2 and a resistor R5. The base of VT2 is connected to the sliding contact of RV1 via fixed resistors R1, R2 and R3. A polarity reversing switch SW3 is coupled to variable resistor RV1 such that reversal can only be carried out: when RV1 is at a minimum. A capacitor C3 is switched into the base circuit of VT2 to form a time constant circuit with R 1 and R2 by which any sudden alteration of RV1 causes a gradual change in VT2 base voltage, load current and motor speed. The time constant is reduced by shorting out R1 by SW1. Resistor R6 discharges capacitor C3 when the delay is not required. The pulsating voltage is applied to the base of VT2 via capacitor C2 and resistor R4. The full-wave rectified voltage is smoothed by capacitor Cl.</p> |
