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Resistance welding which employs three-phase alternating current primarily to overcome the demands of high-power loads on existing power lines and facilities.
Line currents in three-phase systems require only 1/6 to 1/4 of the current needed for single-phase equipment of the same welding capacity.
Additional advantages are:
(1)A machine power factor typically over 85%
(2) Identical (i.e., balanced) current demands on each leg (or line) of a three-phase power source
(3) The same secondary current regardless of the inductive load introduced into the throat of the welding machine
(4) Lower installation cost compared to single-phase
From the welding viewpoint, advantages include:
(1) less tendency for metal expulsion;
(2) longer electrode tip life;
(3) less sensitivity to tip size;
(4) self regulating secondary current;
(5) more uniform distribution of current during projection welding;
(6) easier welding of aluminum, brass, magnesium and other non-ferrous metals, with less electrode pickup.