GB726556A - Improvements relating to voltage control means - Google Patents

Abstract

726,556. Automatic control systems for electrostatic precipitators. HEINRICH, D. O. Feb. 7, 1953, No. 3521/53. Addition to 705,604. Class 38 (4). In an automatic voltage control system in which the electrode voltage of a precipitator is progressively raised until the electrode current rises above a predetermined value, at which point a current sensitive relay reverses a servomotor actuating the supply voltage regulator so as to reduce the voltage as in the patent Specification; the voltage is reduced immediately after the current increase, but is not raised again until after a time delay. The precipitator P is supplied via rectifier Re and high-voltage transformer T from the voltage regulator MCR actuated by a reversible A.C. motor M. Under normal conditions, relay R is energized from the A.C. supply and energizes a delay relay DR over contact r1 Relay DR energizes the motor M over contact dr to raise the voltage until the precipitator current operates relay OL, which is energized by a current transformer CT. Relay OL opens contacts ol so that relay R is de-energized, contact r1 changes over to de-energize relay DR and to energize the motor M to lower the voltage. Contact r2 shorts out the relay OL which resets contacts ol to re-energize relay R. This relay has a short time delay and during this delay the voltage continues to be lowered. Then the relay resets contacts r1 and r2 to reenergize the main delay relay DR and to put relay OL back into circuit. The voltage regulator now remains stationary and unless the relay OL is again operated to again reduce the voltage, the relay DR closes after the delay period, and the motor M once more raises the voltage and the cycle is repeated. The operation of the relay OL may be damped to ignore small disturbances, and the motor may be arranged to lower the voltage faster than it raises it.