Device for controlling the effective value of an alternating load voltage

1,047,477. Switching systems; discharge lamps; converting. SIEMENS-SCHUCKERTWERKE A.G. July 30, 1963 [July 30, 1962], No. 30259/63. Headings H2F and H2H. A circuit for controlling the current to a load 12, Fig. 1, from an A.C. source 11 comprises a saturable choke 13 in parallel with a thyratron or thyristor 14 fired on positive half cycles. It is stated that after the first cycle the choke saturates on negative half cycles at the same delay angle as that at which the thyristor is fired. The circuit may feed a rectifier or a discharge lamp load 32, Fig. 4, through a filter 38 from a square wave inverter 31. To limit peak voltages across the thyristor a reverse-biased full-wave rectifier 371, 372 is coupled to the choke by a winding 331. The rectifiers can be alternatively connected to a capacitor preferably having a voltage dependent discharge resistor in parallel. The choke may have a rectangular hysteresis loop.