GB689953A - Improvements in or relating to a therapy x-ray tube supply system - Google Patents

Abstract

689,953. Supply system for X-ray apparatus. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Aug. 9, 1951 [Sept. 7, 1950], No. 18771/51. Class 38 (iv). To smoothly and gradually increase the A.C. supply to the primary winding 9 of a H.T. transformer 8 supplying, through a rectifier arrangement 6, an X-ray tube 5, a saturable reactor 12 has A.C. windings 10 in the transformer primary circuit to initially reduce the voltage of the supply thereto. At rest, the reactor 12 has a high impedance as an electron discharge tube 22 in the circuit of the reactor D.C. saturating winding 20 is held non-conductive by a negative bias potential C - connected through contacts 24 of a timer relay 17 to the tube grid 23. This bias potential also charges a condenser 27 shunted between the tube grid 23 and its cathode 25 so that on starting up, when an " X-ray on '' switch 19 is closed to start the timer 18 which energizes the relay 17 to close the transformer supply circuit and open the bias potential supply circuit, the tube 22 becomes conductive, but only gradually due to the charge on condenser 27, which charge slowly dissipates through a resistor 26. Gradually the reactor is saturated by the D.C. supply B +, B - and its impedance drops until the full rated voltage is applied across the transformer primary winding 9.