| 摘要 |
1,101,197. Control of D.C. motors. MEFINA S.A. 5 Sept., 1966 [17 Sept., 1965], No. 39561/66. Heading H2J. A series motor M is supplied from A.C. terminals a, b through thyristor T1 whose gating circuit comprises transistor T2 associated with capacitors Cl, C2. When terminal a is positive, the capacitor C2 is charged through the motor armature and a network comprising resistor R10 which is adjustable manually. The transistor T2 becomes conductive to fire the thyristor T1 when the voltage across the capacitor C2 exceeds a reference voltage developed across the capacitor C1 The capacitor C2 is then discharged through a circuit comprising resistor R9 across which a voltage is developed which represents the motor current, the residual voltage at the end of the discharge period being increased if the motor current rises in value. The duration of the subsequent charging period of the capacitor C2 is thus reduced to advance the firing of the thyristor whereby the motor voltage is increased when the motor is subjected to a greater load. When terminal b is positive, the capacitor Cl is charged through circuit elements R1, C2, R6, D2 and D3, and discharges through resistors R1, R2 when the voltage across terminals a, b changes polarity. The ignition of the thyristor T1 is thus advanced when the mains voltage drops to avoid unwanted variations in the motor torque. |
