Prevention of Back Corona Discharge in an Electrostatic Precipitator Using Asymmetrical Rectangular AC Voltage

The aim of this article is to prevent back corona discharge using asymmetrical rectangular ac voltage. The experimental electrostatic precipitator (ESP) consisted of a high-voltage application wire electrode and a grounded plate electrode with a gap in between. Calcium carbonate dust was placed on the surface of the grounded plate electrode. Dc, symmetric, or asymmetric rectangular ac voltage was applied to the wire electrode. The voltage waveform and the current waveform were measured, and a photograph of discharge luminescence on the surface of the dust layer was taken by a digital camera. When dc high voltage was applied, the discharge current increased, and the discharge luminescence was observed on the surface of the dust layer due to back corona discharge. On the other hand, the discharge current did not increase and discharge luminescence was not observed, when the symmetrical ac high voltage at the period of 4 ms was applied. However, the application time of the positive polarity was equal to the negative polarity, and the period was short. Accordingly, it is expected that the collection efficiency is not high in the symmetrically energized ESP. Thus, the effect of an asymmetrical ac energization was investigated. The result showed that the back corona discharge was avoided in the ESP energized by an asymmetrical rectangular ac high voltage with a period of 9 ms including a positive period of 7 ms and negative period of 2 ms.