Hydro-quebec

Jean-Marc Pelletier

Raynald Simoneau

Antonio Di Vincenzo

Jean-Paul Boillot

Yvon Dion

A circuit for controlling the power supply to an electrode of the shielded type, such as that used in a shielded metal arc welding process (SMAW) whereby to protect a user from electric shocks. The control circuit is a protection circuit which serves to protect welders against electric shocks by decreasing the circuit voltage between the electrode tip and the workpiece to be welded. An AC or DC power supply may be used to feed the electrode. The control circuit is comprised of a high impedance voltage source applied to the electrode, a detection circuit for determining the level value of the impedance appearing between the electrode and the workpiece. The detection circuit compares the impedance thus detected with a threshold impedance and generates a control signal when the detected impedance is lower than the threshold impedance. The control signal operates a driver circuit which energizes a power feed device serially connected between the electrode power supply and the electrode itself. The predetermined threshold impedance value is set at about 500 ohms whereby a wet human body will not be subjected to an electric shock by contacting the electrode and the workpiece simultaneously.

Protection circuit against electric shocks during welding

An improvement in an electrical circuit-breaker module of the narrow modular type connectible in stacked relationship with a plurality of modules in an electrical distribution panel. Each of the modules is associated with respective electrical distribution branch circuit and is provided with circuit interruption means for interrupting its associated electrical distribution branch circuit upon the occurrence of predetermined fault and overload currents on the branch circuit. The improvement comprises a controlled switch means mounted in at least one of the modules, without altering the thickness of the module in the vertical plane. The controlled switch means is connected in series with the circuit interruption means and is operable by command means exteriorly or interiorly of the module to assume an open or closed contact condition.

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St-Louis de Terrebonne, Canada

Jean-Marc Pelletier