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.