Short circuit welder

A method for electric arc welding two spaced ends of two metal plates at a groove between said two metal plates by melting an advancing welding wire and depositing said melted wire into said groove to join said spaced ends, said method comprising the steps of:

• (a) providing a power supply creating a series of small width current pulses constituting a welding cycle with a short circuit transfer portion and a plasma arc melting portion, said current pulses in said cycle each having a given electrical polarity of said advancing wire with respect to said two metal plates;
• (b) selecting the polarity of said pulses in said cycle between a first polarity with said wire being positive and a second polarity with said wire being negative, said power supply includes a center tapped inductor with a first portion creating said first polarity and a second portion creating said second polarity;
• (c) connecting said first portion of said inductor across said wire and said plates by closing a first switch;
• (d) connecting said second portion of said inductor across said wire and said plate by closing a second switch;
• and,
• (e) closing either said first switch or said second switch at a selected position in a given weld cycle.

A method of arc welding two spaced ends of two metal plates at a groove between the two plates which defines a gap by melting an advancing welding wire and depositing the melted wire into said groove to form a weld pool that closes the gap between said two metal plates, said method comprising the steps of:

• a) providing a metal electrode;
• b) moving said electrode toward said groove as said electrode is moved along said groove;
• c) melting said electrode by an electric wave, said electric wave including a series of current pulses that constitute a welding cycle, said current pulses in said cycle each having a given electrical polarity with respect to said metal plates;
• d) selecting the polarity of said pulses in said welding cycle between a first polarity with said electrode being positive and a second polarity with said electrode being negative to control the temperature of said weld pool in said groove;
• and
• e) alternating between said first and said second polarity during at least one welding cycle, said alternating polarity being a function of the cumulative amount of energy applied to said electrode and said weld pool in one polarity and the cumulative amount of energy applied to said electrode and said weld pool in the other polarity.