Arc welder with timed control of arcing recovery and means for reducing weight, size, and power loss in the welder

In an arc welder having

• main d.c. power supply means for preparing a main d.c. voltage for welding,
• convertor means for converting said main d.c. voltage into a low frequency square waveform a.c. voltage to apply the same to a welding load, thereby forming normal and inverse polarity periods of application of said square waveform a.c. voltage said welding load, auxiliary power supply means for preparing an auxiliary d.c. voltage for arcing recovery, which auxiliary voltage is higher than said main d.c. voltage, said auxiliary d.c. power supply means having a smoothing capacitor, and
• arcing recovery promotion means for applying said auxiliary d.c. voltage to said convertor means in order to superpose the auxiliary d.c. voltage upon said main d.c. voltage, the improvement comprising:
• said arcing recovery promotion means having timing means for limiting application of said auxiliary d.c. voltage within a predetermined arcing recovery time period following each transition of polarity of said welding load from said normal to said inverse polarity periods, said arcing recovery time period being shorter than each of said inverse polarity periods,
• a diode means, operatively connected between said capacitor and an input of said convertor means, for conducting in response to an excessive transient voltage induced at an input of said convertor means at a time of each said transition of the polarity of said load in order to facilitate absorbing of said transient voltage by said capacitor,
• said timing means having means for detecting a voltage across said capacitor and producing a detection signal in response thereto, and
• means for changing a length of said arcing recovery time period in response to said detection signal.