Lincoln Electric SVM187-A Welding Generator Brush and Commutator Inspection, Examine the brushes

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F-46 TROUBLESHOOTING AND REPAIR F-46

WELDING GENERATOR BRUSH AND COMMUTATOR INSPECTION AND

SERVICE (continued)

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PROCEDURE (continued)

Pitted and Arc Damaged Commutator:

If pitting and arc damage to the commutator is evident, the machine may have been used with badly worn brushes. The brush spring tension may have been too low, or the brushes may have been sticking in the hold- ers. An out-of-adjustment rocker or a serious overload may also cause this condition.

•Examine the inside of the brush covers and other parts that are close to the commutator. If there is a significant amount of solder and debris that has been thrown from the commutator, the armature will need to be replaced and the stator coils must be carefully examined and tested for damage.

•Perform the Weld Circuit Ground and Short

Circuit Test.

•If the brushes are worn out, replace them and re- surface or clean the commutator as needed. If re- cutting is required, the minimum diameter of the commutator is 6.895 in. If the brush springs appear weak, discolored or damaged in any way, replace them as well. The brush holder plates and retainers should be clean, smooth, and undam- aged so the brushes can move freely as they wear.

•Check the rocker position. Be certain that it is aligned with or very close to the factory drill mark. See Figure F.16. IMPORTANT: If the rocker posi- tion requires adjustment, do not over tighten the rocker clamping screw. This screw should be tight- ened to a torque of 70 to 75 Inch-Lbs. Over tight- ening can destroy the rocker.

Uneven Commutator appearance:

If the commutator appears to have some normal col- ored bars and some blackened bars, the armature may be shorted.

•If excessive sparking is observed and/or the weld output is abnormal, the armature should be replaced.

•If the commutator has uneven color, but there is no sign of serious generator performance problems, the commutator may only need to be cleaned by lightly stoning the surface. See caution note on commutator stone usage.

Examine the brushes:

The brushes and springs should all be in place and not be excessively worn. Brushes should be replaced if they are worn to within ¼” of the pigtail lead.

The pigtail lead of each brush should be positioned so it allows free movement of the brush while it wears.

The brushes should be seated so that the face of each brush makes 95% minimum contact with the commuta- tor. Lightly stone the commutator to seat the brushes. See caution note on commutator stone usage.

Examine the brush holders:

The brush holder insulators must be clean and in good condition and all of the hardware must be in place. See Figure F.16. Replace any insulators that are cracked or damaged in any way.

When installing the brush holders, they should be rotat- ed toward the brush retainer (clockwise rotation when facing the brush holder mounting screw.) until they stop. The edge of the brush holder plate should be par- allel with the surface of the commutator and positioned

.030 to .090 from the surface of the commutator. The brush holder mounting screw should be tightened to a torque of 24 to 28 Ft Lbs.

The brush holder plate and retainer assembly must be clean and smooth; nothing should prevent free move- ment of the brushes. All electrical connections to the brush holders must be clean, and tight. The recom- mended torque for 5/16-18 brush holder connection screws is 8 Ft.-Lbs.

SAE-400 SEVERE DUTY