GB1017351A - Improvements in or relating to electrostatic precipitator power supply equipment - Google Patents

Abstract

1,017,351. Control systems for electrostatic precipitators. STANDARD TELEPHONES & CABLES Ltd. Jan. 6, 1964, No. 556/64. Heading H2H. Power supply equipment for electrostatic precipitators includes means for periodically increasing the voltage applied thereto and further means responsive to arcing in the precipitator to effect a momentary reduction or disconnection of the applied voltage and thereafter to re-instate the supply voltage at a value lower than that at which the arcing occurred. An electrostatic precipitator EP is supplied from an A.C. source by way of a regulator DR, driven by a reversible motor RM, a contactor CR and a rectifier RC. Initially a time switch TS is operative to close contact ts1 once or twice a minute to energize the motor RM to drive the regulator DR in a direction to increase periodically the voltage applied to the precipitator EP during which operation a capacitor C charges by way of a rectifier MR2. On the occurrence of arcing in the precipitator the capacitor C discharges by way of a rectifier MR1 and whilst discharging energizes the relay winding RL1/3 to operate its contacts rl1À1 ... rl1À3. During the discharging period of the capacitor C therefore the contactor CR is de-energized to disconnect the precipitator from the supply; the circuit to the " raise " field R of the motor RM is broken and the circuit to the " lower " field L of the motor is completed by way of a relay winding RL2/2, thus the motor RM drives the regulator DR in a direction to decrease the voltage output therefrom. Since the relay RL2/2 only holds in for the period whilst the motor RM is starting the regulator DR is only operative to decrease the voltage setting a small amount. When the capacitor C completes its discharge relay RL1/3 is de-energized whereupon the contactor is re-energized to connect the precipitator to the supply at the lower voltage setting, the " lower " field L is de-energized and the " raise " field R is re-energized and the cycle repeats. Push-buttons PB1, PB2 allow manual control of the apparatus. In other embodiments complete disconnection of the supply by the contactor CR is replaced by a partial reduction in the supply voltage using a tapped transformer or a series reactor.