GB1115336A - Improvement to safety and control systems for burner type heating installations - Google Patents

Abstract

1,115,336. Control of A.C. motors. COMPAGNIE ELECTRO-MECHANIQUE. 5 July, 1965 [8 July, 1964], No. 28415/65. Heading H2J. [Also in Divisions F4 and G1] The starting winding 1b of a shaded pole single-phase motor 1 driving the fuel supply equipment of a burner (not shown) is in serieswith a delay tripping element 5 of a cut-out and with either contacts 2a which are opened by the action of a photo-conductive cell 3 detecting the flame of the burner or a parallel arrangement of a capacitor (11) and the photoconductive cell, Fig. 3 (not shown). When a thermostat 6 closes its contacts a relay 2 is energized and closes contacts 2a, 2b to start the motor and energize an ignition transformer 8 and open contacts 2c to take the photo-cell 3 out of circuit. After a predetermined time the tripping element 5 of the cut-out closes contacts 5b to connect the photo-cell across the relay 2 and if the burner has ignited the reduced resistance of the cell de-energizes the relay 2 so that the contacts 2a, 2b open to de-energize the starting winding and the ignition transformer and the contacts 2c close to keep the cell in circuit. The contacts 5b may be replaced by a thermistor. In a simplified circuit, Fig. 1 (not shown), the contacts 5b and 2c are omitted. In the circuit of Fig. 3 (not shown), the capacitor (11) has the same impedance as the starting winding (1b) of the motor and therefore the current in the starting winding is limited only by its resistance and by the resistance of the element (5) of the cut-out. In the presence of a burner flame, however, the photo-cell (3) short circuits the capacitor and the current in the starting winding drops.