Arc welder power supply with fail-safe voltage reducing circuit
AssigneeMiller Electric Manufacturing Company
InventorsDon J. Corrigall, Marvin L. Schiedermayer
Life of this patent
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Abstract
A fail-safe voltage reducing circuit for an arc welder. The welding transformer has two primary windings connected in parallel across a power source. After an arc is struck, if the arc is then broken for a predetermined time period, the circuit automatically disconnects one of the primary windings from the power source, thereby reducing the voltage across the welder's output terminals to a safe standby voltage lower than the full open circuit voltage. If the voltage has not been reduced after a second predetermined time period, the fail-safe feature of the circuit automatically disconnects both primary windings from the power source, thereby completely removing all power from the welder.
Claims6
In an arc welding power supply of the type including transformer means having its primary side connectable to an A.C. power source and having its secondary side connected across output terminals connectable to a welding electrode and a work piece, respectively, the improvement:
- wherein the primary side of said transformer means comprises first and second primary windings connected in parallel, and the secondary side of said transformer means comprises first and second secondary windings connected in series, so that full open circuit voltage is applied across said output terminals when both primary windings are connected to the power source, and so that a standby voltage lower than the full open circuit voltage is applied across said output terminals when only one of said primary windings is connected to the power source;
- and comprising
- voltage-reducing circuit means, connected in said secondary side of said transformer means and responsive to the absence of welding current in said secondary side for a first predetermined time period, for disconnecting said second primary winding from the power source to reduce the voltage across said terminals to said lower standby voltage.
Dependencies are inferred from the claim text.