GB738002A - Improvements relating to pulse generating circuits - Google Patents

Abstract

738,002. Pulse-generating circuits. BRITISH THOMSON-HOUSTON CO., Ltd. May 20, 1953 [May 21, 1952], No. 12864/52. Class 40 (6). In a pulse generator of the type in which energy is stored in a pulse-forming network and is periodically discharged into a load a saturable reactor which has a very small inductance when the core is saturated is connected in series with the discharge circuit thus preventing a rise of reverse voltage across the switching device or delaying such a rise until the discharge device has de-ionized. Fig. 2 shows a pulse generator in which the pulse-forming network a is charged from a voltage source and is periodically discharged through the primary of transformer d when the gas-discharge tube c is fired, the transformer d serving to match the load to the pulseforming network a. The saturable reactor b is in its unsaturated state when network a has been charged so that when tube c is fired the reactor b presents a high impedance until the current flowing through it causes it to saturate and present a very small impedance. At the end of the generated pulse if there is a residual reverse voltage in transformer d or network a the current flow in reactor b rapidly brings it to its high-impedance state so that the reverse voltage is dropped across reactor b instead of across tube c until after a time delay the reactor again saturates. The reactor may be connected in the anode circuit of the tube c. In a modification shown in Fig. 3 a pulse is generated to fire an ignitron e the output current being limited mainly by the saturable reactor band in which the network b, g reduces the rate of rise of the reverse voltage appearing across the discharge tube c at low pulse recurrence fre. quencies. In a further modification, the Figure (not shown), the saturable reactor has an additional winding which is fed through a choke with polarizing current from a D.C. supply so that when the discharge tube is triggered the reactor is already in its saturated condition and the network immediately discharges into the load. The rate of change of flow which can be controlled by the polarizing voltage supply can be made relatively small with small eddy current losses in the core. Specification 585,359 is referred to.