Yale MPB040E Manual page 107

0620 YRM 0294
Problem
1. Flashover causes
burning of the
ends of the com-
mutator bar.
2. Open circuit in
winding causes
deep burning of
adjacent commu-
tator bars.
3. Overheating cau-
ses damage to
varnish insulation.
Brush and commutator
damage occurs when the
high commutator hits and
forces the brush up. Arc-
ing and burns occur as
the brush moves back
down to the normal sur-
face. Check for loose or
high commutator bars.
Table 2. Commutator Problems (Continued)
Possible Cause
• Motor has been
too hot. Wrong lift
truck for the appli-
cation.
• Motor has been
stalled.
• Open armature
winding.
• Open field coil.
• Motor has been
stalled. (High com-
mutator bars at
each brush posi-
tion can occur if
the motor is stal-
led.)
• Motor has been
too hot.
Brush and Commutator Inspection
Illustration
High commutator bars at each brush position can 1.
occur if the motor is stalled.
Rapid brush wear from high commutator bars. 2.
9