Abstract: An a.c. operated arc welding current supply unit comprises a frequency converter of the series capacitor type and operating with a half period which is substantially less than the average duration of the current and voltage transients caused by short circuits through droplets of weld material during welding. The frequency converter is connected to welding electrodes through a transformer in series with a rectifier to provide direct current for the welding electrodes, and the frequency converter is associated with a control device for maintaining the operating frequency of the converter constant, thereby maintaining the arc power substantially unchanged irrespective of changes in load caused by the welding operation.

Abstract: Initial torch height is acquired by moving a plasma torch toward a workpiece while operating in a pilot mode. The downward movement of the torch is halted when a current sensing relay coupled to the main arc supply senses the transference of the main arc.In a preferred embodiment, the downward movement of the torch is continued until a fixed period of time has passed after the main arc ignition has been sensed.

Abstract: An apparatus for spray-arc welding includes a controllable current source, means for feeding a wire-like consumable electrode of additive material to the weld location; and a control unit for automatically adjusting the current source in dependence upon the weld sequence. The control unit includes means for dividing the welding sequence in a controlled manner into intervals of high and low mean power, by intermittently increasing and decreasing the output of the welding current source in relation to the average output corresponding to the set rate of feed of said wire-like electrode and to the selected length of the arc; and means for preventing the commencement of a high-power interval before the momentary output voltage has fallen to a given value.

Abstract: An apparatus for short-arc welding comprises a controllable current source, means for controllably feeding a consumable wire electrode to the weld location, and a control unit for automatically adjusting the current source in dependence upon the welding sequence. The current source is arranged to provide welding periods divided into short-circuit intervals, arc intervals and optionally also rest intervals. For the purpose of automatically adjusting the welding sequence to changes in the supply of electrode material to the weld location, the control unit includes means for adjusting the power output delivered by the current source as a predetermined function of the duration of at least one of said intervals in a sequence of welding periods.

Abstract: An apparatus for short-arc welding comprises a controllable current source, means for controllably feeding a consumable wire electrode to the weld location, and a control unit for automatically adjusting the current source in dependence upon the weld sequence. The current source is arranged to provide welding periods divided into short-circuit intervals, arc intervals and optional rest intervals. The control unit includes means for continuously adjusting the relationship between arc interval energy and short-circuit interval energy in accordance with a predetermined function.

Abstract: A plasma torch system is provided which creates a pilot arc having high instantaneous power and low average power. The pilot arc ignition circuit reduces the pilot arc duty cycle by pulsing on the pilot arc and then extinguishing it. A plasma torch disclosed also reduces RF noise in the line by eliminating the additional spark gap typically used in the power supply circuit and by placing the triggering circuit on or adjacent the torch handle.

Abstract: A plasma torch circuit includes a control for initially setting the torch at a desired height above a workpiece during the time the non-transferred arc exists between the torch cathode and the torch tip. Measurement is made of the voltage between the cathode and the workpiece, and that voltage is compared to an input for controlling torch height. During transferred arc operation, a reference is initially created by storing the cathode-to-workpiece voltage occurring immediately after the transferred arc is turned on, and using the latter stored voltage as a reference for torch height maintenance.

Abstract: An a.c. operated arc welding current supply unit comprises a frequency converter of the series capacitor type and operating with a half period which is substantially less than the average duration of the current and voltage transients caused by short circuits through droplets of weld material during welding. The frequency converter is connected to welding electrodes through a transformer in series with a rectifier to provide direct current for the welding electrodes, and the frequency converter is associated with a control device for controlling the operating frequency of the converter in a manner such that it is substantially inversely proportional to the square of the input voltage of the current supply unit, thereby maintaining the power output of said unit substantially unchanged irrespective of changes in load caused by the welding operation and irrespective of variations in said input voltage.

Abstract: An a.c. operated arc welding current supply unit comprises a frequency converter of the series capacitor type and operating with a half period which is substantially less than the average duration of the current and voltage transients caused by short circuits through droplets of weld material during welding. The frequency converter is connected to welding electrodes through a transformer in series with a rectifier to provide direct current for the welding electrodes, and the frequency converter is associated with a control device for controlling the operating frequency of the converter in a manner such that it is substantially inversely proportional to the square of the input voltage of the current supply unit, thereby maintaining the power output of said unit substantially unchanged irrespective of changes in load caused by the welding operation and irrespective of variations in said input voltage.