| 摘要 |
697,947. Control of D.C. motors. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. March 26, 1952 [April 21, 1951], No. 7731/52. Class 38 (iii) Series traction motors 1-4 are supplied from a single-phase source 16 through a transformer 18 having a multi-tapped secondary winding, separate pairs of rectifiers 46 being provided for each motor. During the accelerating operation each of the motors is energized through its own rectifier-assembly and the secondary voltage of the transformer is increased by movement of a master controller M, on the early notches of which the motors are started with weakened field excitation, the shunting contacts Mg-Mj being closed. After the maximum-voltage, full field, motoring position has been reached, high-speed operation with weakened field excitation is introduced, the motor voltage being at first slightly reduced and then gradually restored to its maximum value. During braking operation each of the motor armatures is disconnected from the supply and is shunted across a resistor, the several field windings 22 being energized with rectified current from low-voltage tappings of the transformer. As shown, the series field windings are all connected in series during braking operation and are supplied through the pair of rectifiers 46 associated with the first motor, the field circuit being completed through a variable resistor 66. The supply voltage for the field windings may be slightly increased to provide a second stage of braking operation. In a modification, Fig. 2 (not shown), each of the series field windings is energised during braking operation through its own rectifier assembly. |
