| 摘要 |
<p>1289489 Burner controls ATELIERS DE LA MOTOBECANE 23 Dec 1969 [27 Dec 1968] 62650/69 Heading F4T In a burner ignition and control system, sparks are generated between an electrode and the burner body by a capacitor C 0 discharging at intervals through the primary N 1 of a transformer E and a thyristor TH 0 which is triggered at the required frequency by a trigger circuit CD, the sparks initially igniting the burner, then being used for flame detection by inducing oscillations in a detector circuit, the oscillations having different decay times, due to flame ionization, according to whether or not a flame is present. The detector circuit comprises a coil N 3 having a small number of turns and a capacitor C 2 , and when no flame is present the oscillatory decay of this circuit blocks a transistor T 1 for a time t which will be longer than that required for a capacitor C 3 to charge up and trigger a unijunction transistor UJT 2 to produce a pulse which is fed via a diode D 4 to capacitor C 4 of a safety circuit S 1 . After a predetermined number of pulses, the charge on C 4 fires transistor T 2 which in turn triggers thyristor TH 2 to by-pass a relay RL which then opens a switch M<SP>1</SP> and actuates the electromagnetic valve EV to cut-off the fuel supply. If a flame is present, t will be less than t 1 and the capacitor C 3 will discharge through resistor R 9 . A second safety circuit S 2 detects abnormal operation of the system and is normally rendered inoperative by the pulse from UJT 2 produced by the first (ignition) spark which detects absence of flame. The pulse triggers thyristor TH 3 to prevent charging of capacitor C 5 . If the electrode and burner are shortcircuited, no spark will be produced and TH 3 will not be triggered so capacitor C 5 will charge up until UJT 3 is triggered, thus triggering thyristor TH 2 which actuates the relay RL opening switch M<SP>1</SP> and cutting the Fuel supply via valve EV.</p> |
