Abstract: A back corona detector that reduces current flow to the plates of an electrostatic precipitator when a corona occurs between a plate and the dust layer that forms on the plate thereby minimizing the corona condition. The ramping voltage in a transformer/rectifier set under usual operating conditions will vary proportionally with current flow. At the onset of a back corona condition, a comparator senses a sudden increase in current with respect to the voltage indicating that the current is being consumed to maintain the corona rather than providing for particulate precipitation. A current set-back circuit is then pulsed periodically so that the current is continuously reduced until the voltage/current relationship is maintained at the knee of the voltage/current curve.

Abstract: A control system for automatically maintaining a maximum output voltage across the electrodes of a precipitator under varying load conditions without requiring manual readjustment of sensitivity controls. A spark threshold detector provides a threshold crossing signal when a spark occurs across the electrodes of the precipitator. Control circuitry including a ramp generator is responsive to the threshold crossing signal for providing a ramp signal which is effective to vary the voltage applied to the precipitator as a function of the desired spark rate. A sensitivity adjust circuit produces a compensating signal proportional to the magnitude of the ripple on the voltage applied to the precipitator. The DC level of the spark threshold detector is adjusted in accordance with the compensation signal so that the detector is insensitive to variations in the ripple whereby the predetermined spark rate is automatically maintained.