GB521316A - Improvements in and relating to apparatus for the electrostatic precipitation of suspended particles from gases - Google Patents

Abstract

521,316. Automatic control systems for electrostatic precipitators; converting A.C. to D.C. SMETHURST, H., MILN, P. M., and METROPOLITAN - VICKERS ELECTRICAL CO., Ltd. Nov. 15, 1938, No. 33234. Drawings to Specification. [Classes 38 (ii) and 38 (iv)] Voltage control.-Apparatus for electrostatic precipitation of dust &c. is operated at maximum voltage by automatic control thereof in accordance with the frequency "snapping" or flashing-over. An electric motor controlling a moving iron induction regulator in series with a transformer and commutator rectifier has forward and reverse switches controlled by separate banks of contacts in a ratchet-operated stepping switch which is moved forward one contact at each snap, its actuating coil being fed from a current transformer through filter circuits eliminating rectifier ripple. A timing switch closes, say, every five minutes to cause voltage raising or lowering if required, according to the position reached by the stepping switch, which is then reset. The duration of each " raise " is determined by the occurrence of a " snap," that of each " lower by an auxiliary relay, preferably thermal, with potentiometer for adjustment. A time-delayed over-current automatic-releasing cut-out in the precipitator circuit operates a second stopping switch associated with another timing switch so that the cut-out and the whole system are locked out should it operate a given number of times in say half an hour. Interlocks ensure lowest voltage position of the regulator for restarting. Manual control of the regulator motor by push-buttons may be obtained after actuating a normal change-over switch disabling the automatic control. To ensure correct polarity of precipitator electrode a polarized relay in the high or low voltage circuit causes a momentary rupture of the circuit of the motor of the rectifier or reverses the low tension supply. Supervisory indicating lamps and an audible alarm are provided. The system which is not confined to mechanical rectifiers, is fully described with a circuit diagram.