GB601811A - Improvements in or relating to the control of alternating current electric supply circuits - Google Patents

Abstract

601,811. Supply systems for consumption apparatus. GENERAL ELECTRIC CO., Ltd. and STEADMAN, E. J. Dec. 31, 1945, No. 35307. [Class 38 (iv)] An arrangement for ensuring that a load circuit, more particularly an X-ray contactor coil 2, is operatively connected to an A.C. supply 11 at the zero point of the A.C. cycle, comprises rectifiers 9, 10 connected in series opposition with the coil such that at least the first rectifier to become conducting, is short circuited upon current flowing through it. Closure of an exposure switch 11 energizes, when the A.C. supply polarity is correct, the relay 19 through rectifier 9. Relay contact 17 thereupon closes to complete the circuit for the coil 22 of relay 20 through rectifier 10 which becomes conducting upon reversal of supply polarity also to energize simultaneously, the contactor coil 2 and a clutch coil 23 coupling a timing device (not shown) to a synchronous motor 15. Relay contact 18 closes to short circuit the rectifier 10 and the contactor coil remains energized until its circuit is opened by contacts 12 of the timing device. Resistance 24 may be adjusted to cause the contactor to open at the zero point in the A.C. cycle. In modifications, Figs. 2 and 3, not shown, an additional rectifier and associated short circuiting contacts may be provided in order to avoid the use of high speed short circuiting relays in the arrangement shown. The short-circuiting contacts of the third rectifier may be operated by the contactor coil 2. Specification 601,808, [Group XXXVII], is referred to.