GB1363421A - Electrical control - Google Patents

Abstract

1363421 Burner controllers CAV Ltd 30 Sept 1971 [6 Oct 1970] 47380/70 Heading F4T [Also in Division F1] An electrical control circuit for a hot gas generator has a valve 15, Fig. 3, for controlling fuel-gas flow to a combustion chamber 10, an igniter 16, means LRP, Fig. 1, for sensing ignition, a timer motor TM operating switches CS1 to CS12 of which switch CS9 is operated at a predetermined time, e.g. 52 seconds, after motor TM turns on to open valve 15, switch CS3 being operable to render the ignition sensor LRP operative at a predetermined interval, e.g. 3 seconds, after valve 15 opens, sensor LRP turning off the fuel supply if ignition has not occurred, and an auxiliary timing circuit including a switch SR1 in series with switch CS9 and arranged to open after a further predetermined time, e.g. 6 seconds, following opening of valve 15 to cut-off fuel supply, switch CS10 being operated after switch CS3 but normally before opening of switch SR1 to maintain the fuel supply and being arranged so that if switch CS10 does not operate indicative of the failure of motor TM and therefore of the possible failure of switch CS3, the fuel is cut-off at the end of said further predetermined time by opening of switch SR1. After manually operating a switch 21 and a switch GRL5 associated with a gas regulator, start-up is initiated by pressing, and holding pressed, push-switch SB, correct start-up only being achieved if SB is released in the period 8-11 seconds following the start. At start-up (0 seconds) timer motor TM and a lubricant pump motor 20 are energized, switch OP closing when correct lubricant pressure is achieved. At 2 seconds, switch CS8 closes and capacitor C1 charges up via resistors R1, R2 so that relay SR operates at 9 seconds to close SR1. Others of contacts CS1-CS12 and other relays MR, TR act to extinguish light WL and operate light TL during normal running. At 13 seconds, switch CS12 energizes a start motor 17 driving a shaft 18 carrying a turbine 12, Fig. 3, rotated during operation by the hot gases from combustion chamber 10, and compressors 13, 14 giving respectively primary air to burner 11 and secondary air. A switch LPP senses that a sufficient inlet pressure to chamber 10 from compressor 14 is maintained during a purge period, and the ignition sensor LRP is also a switch sensing this pressure, a high-limit pressure switch HAP also being provided. Switch CS11 energizes an ignition transformer 16 between the 47 and 57 second times. At 52 seconds, CS9 energizes valve 15 and if LRP senses ignition by 55 seconds, when CS3 opens, operation continues. If no ignition is sensed CS6 and relay MR act to close valve 15 . After CS8 opens at 50 seconds, capacitor C1 discharges through relay SR to continue energizing its coil until, at 58 seconds, SR1 opens. However, if timer motor TM is still functioning correctly, CS10 has closed at 56 seconds to form a hold-circuit for valve 15. If the motor TM fails at 52 seconds, for example, SR1 cuts off the gas at 58 seconds. If CS8 fails to operate at 50 seconds to discontinue charging of C1 then as soon as CS9 or CS10 close (at 52 seconds, 56 seconds respectively) to energize valve 15, a fault current flows via resistor FR to blow a fuse 25 causing shut down. An operation checking relay CR has a contact CR1 which only allows CS10 to energize valve 15 if CS5, CS6 operate correctly. The starting sequence terminates at 115 seconds when CS12 stops start-up motor 17, and CS1 stops timer motor TM at 120 seconds. When correct operation is achieved the gas regulator valve and associated switch GRLS are moved to a "run" position.