Discharge lamps supply from three phase lines - provides remote switching of inductors from neutral line using auxiliary and main inductances

摘要

The system supplies and switches cold cathode discharge lamps fed from a three-phase supply. The switching of shunting inductors is intended to reduce the power dissipated. Switching control is remote and transmitted by the neutral line. Each lamp circuit has a main and auxiliary inductance. The auxiliary inductance is shunted by the control circuit (4) fed from a clock source. Shunting is achieved by switching into conduction a triac (30) which is fed from a series diode (21)-diac (27)-resistor chain shunted to one phase line (6) by capacitors. The diac-triac circuitry acts as a controlled oscillator providing the gating power. Protection against overvoltage is provided by a parallel DC circuit (28,90) across the triac.