| 摘要 |
1,151,087. Converting. ALLM€NNA SVENSKA ELEKTRISKA A.B. 12 Aug., 1966 [13 Oct., 1965; 21 Oct., 1965], No. 36117/66. Heading H2F. Series connected thyristors are fired simultaneously by energy taken from the voltage divider through a controlled semi-conductor element. In Fig. 1, one thyristor 1, 2, from each of two series chains of thyristors connected in parallel, receives a firing pulse from the capacitor 7 through a light-controlled thyristor, transistor or diode 9. The capacitor 7 is charged through a diode 8 from the voltage divider 3, 4, 6, 5, 15 arranged as shown. Charging occurs only during the forward biased non- conducting period of the thyristors. Conventional current limiting resistances or inductances 10, 11 and voltage limiting Zener diodes, diodes or non-linear resistances 12, 13 are provided. Thr resistance 14 ensures that the trigger electrodes are negatively biased during the reverse biased half-cycles of the thyristors. Different voltage divider constructions may be used (Fig. 2, not shown). The capacitor 7 may be charged through a transformer 25 (Fig. 3). In order to charge the capacitor 7 during the reverse half-cycle the polarity of transformer 25 is reversed. Preferably a step-down transformer is used to match the firing signal to the thyristor. A full wave rectifier may replace diode 8 (Fig. 4, not shown). Reference has been directed by the Comptroller to Specification 1,060,352. |
