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Miller Electric Manufacturing Company

Miller Electric Mfg. Co.

Robert L Risberg

Jon O Reynolds

A pulse arc welding power supply incorporating one or more series resonant converters (SRC) for converting D.C. power to A.C. power which is then rectified to supply welding current. Each series resonant converter includes a series resonant tank circuit consisting of a capacitor, an inductor and the primary winding of a transformer whose secondary winding supplies current to the welding arc. The undesirable secondary output capacitor of the prior art is eliminated, as all the capacitance in the series resonant circuit is located on the primary side of the transformer. Current sensors sense the ringing current in the resonant circuit and also the load current and produce respective feedback signals which are used to control the switching frequency of an SCR bridge in the tank circuit, thereby maintaining the welding current at a desired value. Inner and outer current regulating loops, including a ramp generator, compensate for non-linearity in the continuous conduction mode of the SRC by limiting the switching frequency of the SCRs. a fault-predicting circuit also further limits the switching frequency in the continuous current mode for additional protection.

Stabilized welding power source including a series-resonant

The position of the main rheostat on an arc welding machine determines the pre-set welding current. An operator, working at a location remote from the welding machine, carries a pen-type adjustable rheostat which carries calibrations indicative of various percentages of the pre-set welding current. There are no extra electrical connections, such as wires, between the remote rheostat and the welding machine. If the operator wishes to change the magnitude of the welding current, he need not return to the main rheostat at the welding machine, but instead merely sets the remote rheostat for the percentage of pre-set current desired, and inserts the remote rheostat between the electrode holder and the workpiece. The minimum resistance of the remote rheostat is sufficiently high to prevent an arc from being struck. A current transformer in the welding machine senses the output (calibrating) current flowing through the welding cable. A signal proportional to the desired welding current reference is compared with a stored value of the present welding current reference to produce a control signal which is fed to an up/down counter whose output is the stored welding current reference. The welding current reference is thus either increased or decreased until it reaches the value called for by the adjustable remote rheostat. After a few seconds, the operator removes the remote rheostat from the electrode holder, and the welding current reference will now be at the precise desired value to produce the desired welding current.

Wireless remote control for electric welder

A solid state, current source, polyphase inverter induction motor drive is disclosed wherein the current source is derived from a constant potential buss. Each side of the buss is connected to the inverter via a separate chopper. The choppers normally operate in unison to supply a controlled current to the inverter. Each time the inverter sequence is to be advanced, the chopper current is reduced to zero on the side of the inverter, either positive or negative, that requires a commutation. Chopper current is then reinstigated and feeds the next set of inverter thyristors in the inverter sequence. Alternative means for rendering the current source non-inductive during inverter commutations, and transformerless means for providing motor voltages well above rated voltage are also disclosed.

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Brookfield, WI, United States of America

Robert L Risberg