Miller Electric Manufacturing Company

Electro-craft Corporation

Marvin L Schiedermayer

Don J Corrigall

Dennis R Hipkins

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.

Arc welder power supply with fail-safe voltage reducing circuit

A closed control system for controlling the operation of a multiple horsepower brushless direct current motor wherein a current feedback signal representative of the effective motor drive current is constructed from the instantaneous currents flowing in the stator windings. Protective circuitry is provided to shutdown the output power stages in the event of component failures to prevent catastrophic failure of other components in the system.

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Appleton, WI, United States of America

Marvin L Schiedermayer