USAGE; SPOT WELDING OF COMMUTATORS AND ARMATURE LOOPS IF MOTOR ENGINE AND AUTOMOBILE ENGINE,WHOSE WIRE DIAMETERS ARE RATHER LARGE. FEATURES; USING THREE PHASE SECONDRY OUTPUT AC CURRENT TO WELD,CONCENTRATING HEAT,WELDING QUALITY IS HIGH,SETTING WELDING SEGMENT ,MAINTAIN WELDING EVENLY IN A WEEK,STEP-MOVE ,DUAL GUADING POLES CYLINDER CONTROL WELDING DEPTH.