| 摘要 |
1,209,421. Automatic current control. WESTINGHOUSE ELECTRIC CORP. Feb. 21, 1969 [March 6, 1968], No. 9497/69. Heading G3R. [Also in Division H2] A voltage signal VR represents the desired tractive or braking effort to be supplied by traction motors M1-M4, a voltage signal VL being proportional to the weight of the vehicle. A transistor 5 is turned on when a ramp voltage V1 exceeds the voltage VR, the voltage V2 varying between the values VL and zero according to the state of conduction of the transistor. The filtered voltage V3 is proportional to both the signals VL and VR and is added as bias to the voltage VR to develop a signal across lines 15, 16, which causes the motors to provide the desired tractive or braking effort modified in accordance with the car weight. The motor current is controlled by chopper 23 comprising a main thyristor 24 associated with a commutating capacitor 25 and turn-off thyristor 26, as well as an auxiliary thyristor 27 and reactor 28. For power operation, the motors are connected in parallel, a free-wheeling diode 37 being included in the motor circuit. Two loop circuits are formed for braking, the common branch including resistors 35, 36. The chopper 23 is controlled by pulse generators 39, 40, in accordance with a comparison between the motor currents and the signal across lines 15, 16. A control signal on line 42 is modified by delay circuit 44 to provide the signal VR. A transductor 45 carries the total motor current in either the power or braking connection, its rectified output being applied across Zener diode 50 and resistor 51. The control signal from the load-compensating circuit 1 is developed across capacitor 52, whilst lines 53, 54, convey the triggering signals to the pulse generators 39, 40. The voltage-drop across diode 50 determines the amount of ripple in the motor current. |
