Circuit for interrupting arc discharge in a gas-discharge vessel

A circuit for quenching a transition from a glow discharge to an arc discharge in a gas-discharge vessel for surface treatment of industrial materials with the glow discharge from said gas-discharge vessel, comprising:

• a gas discharge vessel having an anode and a cathode;
• a series network of a rectifier and a first choke continuously connected directly in parallel across said anode and said cathode of said gas-discharge vessel for applying a glow-discharge-sustaining direct current thereto;
• a saturating transformer having a tapped primary winding connected in a series connection with a capacitor, said series connection being connected directly across said series network and said anode and cathode of said gas-discharge vessel, said saturating transformer further having a secondary winding;
• a thyristor having a gate, an anode connected with a positive terminal of said rectifier and a cathode connected with a tap of said primary winding located closer to a terminal of the primary winding connected to said cathode of said vessel than to a terminal of the primary winding connected to the anode of said vessel;
• a series network of a diode and a second choke connected across said anode and cathode of said thyristor with an anode of said diode being connected to said tap whereby the series network of the diode and the second choke is connected in parallel to said thyristor for rapid restoration of a voltage across the anode and cathode of said vessel upon termination of the discharge;
• a control pulse shaper having an input connected to said secondary winding and an output connected to a gate and the cathode of said thyristor for rendering said thyristor conductive upon a drop in voltage sensed by said transformer as a voltage difference between a voltage across said capacitor and a voltage across said anode and cathode of said gas-discharge vessel and representing a transition from a normal glow discharge to an arcing condition in said vessel, thereby impressing upon said vessel a voltage inversion to quench said arc discharge;
• a voltage sensor connected across said anode and cathode of said gas-discharge vessel and responsive to a development of an excess voltage thereacross;
• and
• another control pulse shaper having an input connected to said voltage sensor and an output connected to the gate and cathode of said thyristor for triggering said thyristor into conduction upon a detection of said excess voltage by said voltage sensor.