Abstract: A method and apparatus for providing an ac signal to load terminals, where the signal has a reduced open circuit voltage is disclosed. The apparatus includes an ac current source connected to the load terminals and an open circuit sensor. A control circuit is connected to the source of ac current and to the open circuit sensor, and when the sensor senses an open circuit the control circuit causes the current source to provide a dc signal. The dc signal is created by allowing the current source to provide a signal of only one polarity. The polarity may be either electrode positive or electrode negative. The current source may be either a phase controlled current source or an inverter. The method includes the steps of detecting the presence of an open circuit at the load terminals and causing the ac power source to provide a half wave signal of only one polarity in response to the detection of an open circuit.

Abstract: An induction heater comprises a coupled pair of inverters and an induction head for generating heat, coupled to the second inverter. The output signal of the first inverter which operates at a fixed frequency, is controlled by feedback indicative of the heat output of the induction head. A control circuit processes the feedback information to compensate for power losses in the induction head. The output of the first inverter is electrically coupled to the input of the second inverter, which operates at an adjustable frequency which is selected by the user to optimize heating. The power delivered to the induction head is dependent on the output voltage of the second inverter, which is dependent on the output signal of the first inverter.

Abstract: A welding nozzle retaining ring has a polygon configuration with alternating peaks and straight segments. One segment is cut. The retaining ring is sized such that the peaks lie along a circle having a diameter that is slightly greater than the inner diameter of a welding gun nozzle or similar tubular component. The midpoints of the inner surfaces of the retaining ring segments lie along a second circle having a diameter slightly smaller than the diameter of a groove in a welding gun adapter or similar cylindrical component. With the retaining ring in the adapter groove, the welding nozzle is pushed over the adapter and the retaining ring. The nozzle inner diameter contacts and depresses the peaks of the retaining ring and simultaneously causes the segments to bend around the adapter groove. The retaining ring acts as a circumferential spring that provides a rigid radial connection between the nozzle and the adapter while enabling the nozzle to slide against friction along the adapter.

Abstract: An inverter power supply for use with various voltage inputs is provided. The inverter power supply generally receives 208 VAC single-phase, 208 VAC three-phase, 230 VAC three-phase, 230 VAC single-phase, 460 VAC single-phase, or 460 VAC three-phase power and provides a DC output current for welding, heating or cutting applications. The power inverter circuit includes a first tank circuit and a second tank circuit which are configured in serial or parallel according to a particular voltage input. Contactors, relays, or semiconductor switches respond to control signals from an AC sense circuit in order to configure the inverter power supply for the appropriate voltage input.

Abstract: A power supply for providing an ac/dc output to a load, includes a first source of dc power and an inverter that provides an ac output to the load. A second source of dc power is provided and selectably connects the first and second sources of dc power in series with the load when the output current reverses. In one embodiment the power sources are connected in series with every output current reversal. The first source of dc power is controllable and the magnitude of the dc current is responsive to a current reference signal. A control circuit provides the current reference signal, wherein the current reference signal is pulsed immediately prior to the ac output reversing polarity. The first source of dc power source preferably includes a buck converter that is switched at a variable frequency, depending upon the desired output current. In the event the user selects either an ac or dc electrode negative output a period of electrode positive dc energy is provided at start up to help establish the arc.

Abstract: An operator controllable transformer having a shunt magnetic path with a control coil is provided. The transformer includes phase control circuitry to control the output of the transformer by phase controlling current flow in the shunt coil, thereby controlling the flux through the shunt magnetic path and the flux coupling with the secondary coil. Power for the control circuitry is derived from the current induced in the shunt coil.

Abstract: An induction heater comprises a coupled pair of inverters and an induction head for generating heat, coupled to the second inverter. The first inverter operates at a constant frequency, but the total output current is controlled through pulse width modulation. The output current is rectified and provided as a DC input voltage, proportional to the total output current of the first inverter, to the second inverter. The second inverter operates at an adjustable frequency which is selected by the user to optimize heating. The power delivered to the induction heater is dependent on the output voltage of the second inverter, which is dependent on the input voltage to the second inverter, and the output current of the first inverter.

Abstract: A AC power source for welding is configured to receive three phase power and to provide single phase current to a welding load. The power source includes a three phase transformer with three center tapped secondary windings, a center tapped output inductor, and suitably triggered thyristors between the secondaries and the output inductor.

Abstract: An inverter power supply for use with various voltage inputs is provided. The inverter power supply generally receives 208 VAC single-phase, 230 VAC three-phase, 230 VAC single-phase, 460 VAC single-phase, 208 VAC three-phrase or 460 VAC three-phase power and provides a DC output current for welding, heating or cutting applications. The power inverter circuit includes a first tank circuit and a second tank circuit which are configured in serial or parallel according to a particular voltage input. Contactors, relays, or semiconductor switches respond to control signals from an AC sense circuit in order to configure the inverter power supply for the appropriate voltage input.

Abstract: A welding arc stabilizer including a source of high voltage and a switch for switching the source of high voltage across the electrode and the workpiece in the event the arc rectifies. The high voltage is switched across the electrodes within the completion of the half cycle in which rectification occurred. The source of high voltage includes a resonant LC circuit. An arc sensing circuit, including a resistor, a capacitor, and a zener diode is provided in parallel with the arc. In the event the voltage applied to the electrode and workpiece exceeds the zener diode breakdown voltage, indicating the arc has rectified, an SCR disposed between the resonant circuit and one of the electrode and the workpiece is turned on, thus connecting the source of high voltage to the electrode and workpiece.

Abstract: A transformer having a shunt magnetic path and a shunt coil is provided. The transformer includes control circuitry to control the output of the transformer by controlling current flow in the shunt coil, thereby controlling the flux through the shunt magnetic path and the flux coupling with the secondary coil. The current in the shunt coil is phase-controlled and power for the control circuitry is derived from the current induced in the shunt coil.

Abstract: The present invention provides a GMAW control system for balancing wire burnoff rate with wire feed speed at a weld site. A power source applies a pulsed current to the consumable wire. The width of the peak pulse current is calculated and adapted to maintain a constant optimum arc length as selected by the operator. The controller provides a reference voltage to the power source and the power source provides the pulsed current having a magnitude responsive to the reference voltage signal.

Abstract: A self-contained heat exchange system (10) is provided wherein the fan (14), pump (18), radiator (30), and motor (16) are disposed within a cylindrical flow path (40) defined by a resilient housing (12). In accordance with a preferred embodiment, the housing (12) comprises a double walled, generally annular fluid reservoir (46). Accordingly, the inside wall (44) of the housing defines the airflow path (40), thereby maximizing heat exchange efficiency per unit volume of heat exchange fluid. Moreover, the annular character of the fluid tank (12) in conjunction with the disposition of the pump (18) within the airflow path (40) defined by the annulus, ensures that the pump (18) is always in a primed condition.

Abstract: 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.