Electric dust collecting apparatus having controlled intermittent high voltage supply

Claim 1

An electric dust collecting apparatus having a low voltage power supply driving a high voltage transformer which drives a rectifier circuit which drives dust collecting electrodes and having a thyristor circuit operatively connected between said low voltage power supply and said high voltage transformer, said thyristor circuit being controlled by a thyristor control circuit operatively connected thereto, the improvement comprising: an intermittent control circuit operatively connected between said thyristor control circuit and said thyristor circuit for transforming a D.C. voltage output from said thyristor control circuit into a periodic pulsed D.C. signal, said signal having a constant pulse width and a constant pulse repetition rate and having a constant maximum and a constant minimum voltage level; and a means for adjusting at least one of said constant pulse width and pulse repetition rate and said constant minimum and maximum voltage levels of said periodic pulsed D.C. signal so as to prevent back corona from occurring in said dust collecting apparatus by periodically alternately supplying a high voltage and a reduced high voltage to said dust collecting electrodes.