| 摘要 |
1,042,665. Automatic speed control. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. Feb. 9, 1965 [Feb. 12, 1964], No. 5537/65. Heading G3R. [Also in Division H2] A series motor having armature 1 and field winding 2 is energized through controlled rectifier 4 from A.C. source 3, a transistor 11 becoming conductive to fire the rectifier when the voltage across capacitor 5 exceeds a portion of the back E.M.F. developed across potentiometer 13. A rectifier 12 maintains the current in field winding 2 after the current pulse through the rectifier 4 has terminated. In each of the control positions of the potentiometer 13, the circuit reaches a state of equilibrium which corresponds to a given speed. The capacitor is charged through diode 6 and resistor 7, the diode reducing the peak voltage across the capacitor. In another arrangement, the motor is compound-wound and the transistor 11 is replaced by a four-layer trigger diode associated with a pulse transformer. A further modification employs two back-to-back controlled rectifiers instead of the rectifier 4, for supplying the motor with A.C., these rectifiers being controlled by a pulse transformer having two secondary windings. The four-layer trigger diode is replaced by a bilaterally conducting diode or two diodes in parallel opposition. The series field winding is shunted by a capacitor and inductor constituting a circuit tuned to the source frequency. In another embodiment, the motor is supplied through bridge-connected controlled rectifiers and diodes. Two additional diodes also constitute a bridge circuit with the controlled rectifiers to charge the capacitor through a limiting arrangement including Zener diodes. The trigger circuit comprises two transistors and the capacitor for supplying a switching-on pulse to the rectifier when the voltage across the capacitor exceeds a threshold value. |
