StoningtheCommutator

Table2. CommutatorProblems(Continued)

Problem PossibleCause

Electricalburnson commutatorbarson oppositesidesofthe commutator. • Openarmaturewinding. • Motor has been stalled.

Illustration

Copperwearsrapidly attheedgeofthe commutatorbars. • Operationofthemotorindirtyandabrasiveconditions. • Wrongtypeofbrushes forthismotorandoperation.

Table2. CommutatorProblems(Continued)

Problem PossibleCause

1. Flashover causes burningoftheends of the commutator bar. 2. Open circuit in winding causes deepburningofadjacent commutator bars. 3. Overheatingcauses damagetovarnish insulation. • Motor has been too hot. Wronglifttruck fortheapplication. • Motor has been stalled. • Openarmaturewinding. • Openfieldcoil.

Illustration

Brushandcommutator damageoccurswhen thehighcommutator hitsandforcesthe brushup.Arcingand burnsoccurasthe brushmovesbackdown tothenormalsurface. Checkforlooseorhigh commutatorbars. • Motor has been stalled. (High commutatorbarsateach brush position can occurifthemotoris stalled.) • Motor has been too hot.

1. Highcommutatorbarsateachbrushpositioncan occurif themotorisstalled. 2. Rapidbrushwearfromhighcommutatorbars.