StoningtheCommutator

Table2. CommutatorProblems(Continued)

Problem PossibleCause

Groovesthatarethe widthofthebrushes. • Operation of the motorindirtyand abrasive conditions. • Wrong type of brushesforthismotorandoperation. • Brush pressure is toohigh.

Illustration

Aconditioncalled copperdragoccurs whencopperfrom thecommutator barispulledinto theslotbetween thecommutator bars.Thiscondition willcauseashort circuitbetweenthe commutatorbarsif itisnotcorrected. Thebrusheswillwear rapidly. • Operation of the motorindirtyand abrasive conditions. • Brushholderisnot adjusted electricallycorrectforthe motor. • Wrong type of brushesforthismotorandoperation. • Brush pressure is wrong(toohighor toolow).

Electricalburnson commutatorbarson oppositesidesofthe commutator. • Open armature winding. • Motor has been stalled.

Table2. CommutatorProblems(Continued)

Problem PossibleCause

Copperwearsrapidly attheedgeofthe commutatorbars. • Operation of the motorindirtyand abrasive conditions. • Wrong type of brushesforthismotorandoperation.

Illustration

1. Flashover causes burning of the endsofthecommutatorbar. 2. Open circuit in winding causes deep burning of adjacent commutatorbars. 3. Overheating causesdamageto varnish insulation. • Motorhasbeentoo hot. Wrong lift truckfortheapplication. • Motor has been stalled. • Open armature winding. • Openfieldcoil.

Brushand commutatordamage occurswhenthehigh commutatorhitsand forcesthebrushup. Arcingandburns occurasthebrush movesbackdownto thenormalsurface. Checkforlooseor highcommutator bars. • Motor has been stalled.(Highcommutator bars at eachbrushposition canoccurifthemotorisstalled.) • Motorhasbeentoo hot.

1. Highcommutatorbarsateachbrushpositioncanoccur ifthemotorisstalled. 2. Rapidbrushwearfromhighcommutatorbars.