| 摘要 |
1,114,800. Control of A.C. loads. GENERAL ELECTRIC CO. 19 Sept., 1966 [11 Oct., 1965], No. 41748/66. Heading H2H. A protective circuit for one or more phasecontrolled thyristors to retard the phase angle when the supply is removed in order to limit the subsequent initial current particularly with inductive loads, comprises a magnetic amplifier 21 having a negatively directed bias binding 37 fed by an unregulated voltage through resistors 46, 51 to compensate for line voltage fluctuations, plus a regulated voltage across a Zener diode 43. When the supply is removed, capacitors 61, 62 discharge rapidly, and a capacitor 53 reverse biases diode 54 and discharges through resistors 52 57 biasing a transistor 50 on, hence another capacitor 47 discharges through the winding 37 producing additional negative flux to counter any positive remanent flux from the control windings 34, 34<SP>1</SP>. These are supplied by signals 20, 20<SP>1</SP> which are shunted by diodes 70, 70<SP>1</SP> through resistors 71, 711 when a back-biasing potential due to windings 33, 33<SP>1</SP> and diodes 72, 72<SP>1</SP> is removed by a cessation of the supply 11. |
