GB985327A - Improvement in automatic controllers by utilizing monitored electro-magnetic relays - Google Patents

Abstract

985,327. Automatic control systems. H. J. HAYES. July 9,1963 [April 11, 1962], No. 13897/62. Heading G3R. [Also in Division H2] In an automatic control system for a physical variable of the type in which an electromagnetic relay controlling a regulator is operated by a control signal responsive to the variable, reliability is improved by using two relays A, B which operate together in response to a common signal applied at terminals 7, 8 to the control grids of valves 20,21,the relay contacts A1,A2,A3,B1,B2, B3 being so arranged that should a fault occur in one relay or its associated circuit, the control of the regulator (through terminals 3,4) is maintained by the serviceable relay circuit and an alarm is operated (terminals 5, 6) each time the serviceable relay is energized. A lamp 16 or 17 is energized with the alarm to indicate which relay circuit is at fault. Further relay contacts A4, B4 and a switch 19 ensure continuity of the function of interlock circuits (terminals 9,10). The faulty circuit component may be found by interchanging the corresponding components of the two circuits. Resistors 11,12 prevent a short circuit in the heater circuit of one of the transformers 13,14 making both inoperative. The Provisional Specification mentions the use of a monitored relay arrangement to switch on a stand-by controller and give an alarm when a main controller becomes unserviceable.