Abstract: A control system is interposed between the input terminal (14) and the output terminal (16) of a welding machine (10). An electrical conductor (18) is connected to the input terminal. A ground conductor (20) extends out from the housing (12) of the welding machine (10). An electrode conductor (24) extends from the output terminal (16) to an electrode holding device (26). An electrode (28) is held by the electrode holder (26). The control circuit includes means for connecting welding voltage to the electrode holding device (26) and the electrode (28) when the electrode (28) is connected to a grounded workpiece (50). A control circuit also connects the electrode holding device (26) and the electrode (28) to a lower, safe voltage, when the electrode (28) is disconnected from the grounded workpiece (50). As a result, the welder is protected from electrical shocks when the electrode (28) is disconnected from the grounded workpiece (50). The control circuit is characterized by one, two, three or more SCRs.

Abstract: The electrical ground fault protection circuit (10) includes power and ground LINE connections (12) that are connectable to power (18a, 18b, 18c) and ground lines of an electrical distribution system. They also include power and ground LOAD connections (14) that are connectable to a load (29). Power and ground paths extend from the power and ground LINE connections to the power and ground LOAD connections and include an interrupter (72) having a connect position in which it allows current flow from the LINE connections to the LOAD connections and a disconnect position in which it interrupts such current flow. A ground line monitor (64) detects the presence or absence of a fault condition in the ground line (20). In response to the presence of a fault condition, the circuit switches the interrupter from its connect position to its disconnect position. The power path monitor (66) detects the presence or absence of a fault condition in the power path (18a, 18b, 18c).

Abstract: The electrical ground fault protection circuit (10) includes power and ground LINE connections (12) that are connectable to power (18a, 18b, 18c) and ground lines of an electrical distribution system. They also include power and ground LOAD connections (14) that are connectable to a load (29). Power and ground paths extend from the power and ground LINE connections to the power and ground LOAD connections and include an interrupter (72) having a connect position in which it allows current flow from the LINE connections to the LOAD connections and a disconnect position in which it interrupts such current flow. A ground line monitor (64) detects the presence or absence of a fault condition in the ground line (20). In response to the presence of a fault condition, the circuit switches the interrupter from its connect position to its disconnect position. The power path monitor (66) detects the presence or absence of a fault condition in the power path (18a, 18b, 18c).

Abstract: The control unit comprises an elongated body having a forward torch mounting portion. Rearwards of the torch the body houses a linear potentiometer which includes an upstanding control arm for its movable contact. An off-on switch is located within said body, in a position to be contacted and operated by the control arm. A thumb button controlled sliding control member is attached to the control arm. In use, the user grips the mid portion of the body and places his thumb on the thumb button. He uses a simple linear movement of his thumb to both control the linear potentiometer, for varying the welding current, and to operate the off-on switch, for turning the arc welding machine on and off.