GB762097A - Improvements in and relating to ignition systems - Google Patents

Abstract

762,097. Ignition systems. GENERAL ELECTRIC CO. July 15, 1953 [July 17, 1952], No. 19648/53. Class 7 (4). [Also in Group XXXV] Circuit arrangement.-In a discharge ignition system comprising main and triggering circuits, the main circuit, the input of which is wired to a power source, including in series a main capacitor 17, the secondary 25 of a voltage step-up low-impedance transformer 23 (see also Group XXXV) and an igniter 28 which is connected to the output end of the main circuit, and the triggering circuit, which discharges through the main circuit, including a triggering capacitor 20, a current limiting resistor 21 therefor, and an auxiliary gap 24 in series with the triggering capacitor 20 and the primary 22 of the low-impedance transformer 23, the resistance of the main discharge circuit is less than the minimum value for prevention of oscillation. A high reactance step-up transformer 10 is provided with an air-gap 12 in a magnetic shunt between those parts of the core upon which the primary and secondary windings 13, 18 are wound ; the primary winding 13 is connected via a capacitor 14 to the A.C. power source whilst the capacitor 17 is fed with D.C. from the secondary winding 18 through a selenium rectifier 19. The capacitor 14 serves to limit the circuit current, offset the lagging power-factor resulting from the reactance of the transformer 10, and together with the latter's magnetizing reactance produces a stabilizing effect which minimizes fluctuations in the source voltage; the reactance of the capacitor 14 is greater than the unsaturated magnetizing-reactance of the transformer 10. The rate of sparking of the system is determined by the elements 10, 14, 17, 20 and 21 while the capacitor 17 and transformer secondary 25 comprises a clamped series-resonant circuit when the ignition-plug gap is sufficiently ionized to be conducting. In a modification the main discharge path of the storage capacitor includes both the primary and secondary of the low-impedance transformer which latter may either be of the autotransformer or insulated type. Electrical values and formulae relating to the circuit and components are given. Operation.-The triggering capacitor 20 which is charged more slowly than the main capacitor 17 because of the resistor 21 breaks down the gap 24 and discharges through the primary winding 22, the resulting high voltage in the secondary winding 25 ionizing the gap of the igniter 28 whereupon the main capacitor 17 discharges into the secondary winding 25 and across the igniter 28, some of the energy being stored in the transformer 22, 25 which then discharges to continue the delivery of energy to igniter 28 and to recharge the capacitor 17 with the opposite polarity. This oscillation in the inductance capacitancespark gap circuit continues until the stored energy is dissipated.