| 摘要 |
1,071,439. Semi-conductor switching circuits. BROWN BOVERI & CO. Ltd. Dec. 15, 1965 [Dec. 17, 1964], No. 53192/65. Heading H3T. [Also in Division H2] The current through a load 3 from a D.C. supply 1 is controlled by a power thyristor 4 which is switched on by discharge of a capacitor 8 (charged slowly via members 6, 7) and is switched off by discharge of a capacitor 11 through a series circuit comprising the thyristor 4 and two control thyristors 14, 19. To switch off, the thyristor 14 is fired by discharge of a capacitor 16 and this in turn fires the thyristor 19 to complete the series circuit, conduction ceasing after the discharge of capacitor 11 due to the magnitude of resistors 12, 13. Thyristor 4 may be automatically switched off upon overload by provision of a second firing circuit for the control electrode of thyristor 14, this circuit comprising a load-current-carrying resistor (22), a resistor (23), a diode (24b) and a Zener diode (25), Fig. 2 (not shown). The load 3 may comprise the armature (27) of a separatelyexcited D.C. motor which can be supplied with pulses of adjustable length and/or frequency by triggering the thyristors 4, 14 in accordance with a predetermined firing programme, the motor armature being in series with an inductance (26) for smoothing and transient suppression purposes, Fig. 3 (not shown). |
