Arrangement in electrical welding apparatus

Claim 1

Welding apparatus of the type wherein the welding electrodes for producing an arc are supplied with pulsating direct current derived from an a.c. current supply by means of a controlled frequency converter which substantially increases the frequency of the alternating current, the output of said converter being connected through a transformer and a rectifier to the welding electrodes, wherein the connection between the rectifier and the welding electrodes includes a shunt capacitance having a preselected impedance which is of a low value so as to attenuate the alternating current components of the welding current to an audio level of at most 85 dB at frequencies up to 16,000 Hz, 95 dB in the frequency range of 16,000 to 20,000 Hz and 105 dB in the frequency range of 20,000 to 50,000 Hz, the said connection further comprising means for preventing the capacitor from adversely affecting the rectifier and frequency converter and a choke arranged between the capacitor and the electrodes to support the arc during recharge of the capacitor but for allowing discharge thereof during short circuit periods caused by droplets of molten welding material.