GB1471081A - Power supply apparatus with remote control of power - Google Patents

Abstract

1471081 Power supplies for arc welding apparatus; control of DC motors J SAULSMAN 11 March 1974 10784/74 Headings H2H and H2J Apparatus for controlling the supply of power from a source 24 to a remote arc welding station comprises an operator responsive switch 20 for adjusting the level of power delivered from the source to any value between zero and full power without interruption of the power delivered to the station and for reversing the direction of change in the power delivered from the source without interruption of the power delivered to the station, and a sensor for detecting the change in power delivered. When the switch 20 (or S1) is moved by an operator to the INCR. position, a resistor R1 is connected in circuit and causes a transistor Q3 to conduct but a transistor Q4 is non-conductive. A transistor Q6 conducts and switches on a transistor Q8 which in turn switches on transistors Q9, Q10. Current therefore flows in one direction through a motor M1 which rotates a rheostat in the source 24 to increase the welding current. movement of the switch S1 in the opposite direction causes conduction of both transistors Q3, Q4 but since the base voltage of the transistor Q5 exceeds that of the transistor Q6, the transistor Q5 conducts whilst the transistor Q6 is non-conductive. Transistors Q7, Q11, Q12 are therefore switched on to supply current in the reverse direction to the motor M1 thereby decreasing the welding current. The motor speed and therefore the rate of change of the power delivered to the remote station may be preset by a potentiometer R7 adjusted by a control (29), Fig. 3 (not shown) on the housing 26. The sensor, which is connected to a conductor 34d, is an earphone or headphone supplied by an audio oscillator which is turned on at each operation of the switch S1 and supplies a tone to the welding operator to indicate the change of the welding current. In Figs. 7, 11 (not shown) the welding conductor 15 is used as one of the control conductors 34c, the switch S1 then controlling a circuit supplied with A.C. but isolated by a transformer from the main control circuit to prevent D.C. on the welding electrode being fed to the control circuit.