Taylor-Dunn SC-090-24 Operation, T Roubleshooting And Replacement Parts Manual page 55

3. Measure the commutator undercut depth in
5-places around the commutator.
• If any one of the measurements is less than the
minimum undercut depth specified in
Limits
at the end of this section, then the
commutator must be undercut. Refer to
Commutator
section for information regarding
undercutting the commutator.
4. Inspect the commutator for groves.
• If the commutator is grooved then it must
be machined on a lathe. Do not machine
the commutator past the minimum diameter
specified in
Service Limits
Repair Commutator
regarding machining the commutator.
5. Inspect the commutator for burn marks.
• Burn marks and/or raised commutator segments
90 or 180 degrees apart is evidence of a shorted
armature. A tool called a growler is required to
reliably test for a shorted armature.
6. Inspect the commutator for raised segments.
Raised segments could be a result of a stalled
motor or shorted armature. A tool called a growler
is required to reliably test for a shorted armature.
• If the armature is not shorted then the raised
segments can be removed by machining the
commutator. Do not machine the commutator
past the minimum diameter specified in
Limits
section. Refer to
section for information regarding machining the
commutator.
7. Visually inspect the armature windings for burnt
insulation. Burnt insulation is a direct result of
motor overheating and could lead to a shorted
armature.
• If the insulation is cracked or burnt, then it is
recommend that the armature or motor be
replaced.
Note: If the armature has been burnt then there is
a good possibility that the field windings may
also be burnt. Symptoms indicating a shorted
field include high motor current, lack of power
and possibly excessive speed.
Maintenance, Service, and Repair
Service
Repair
section. Refer to
section for information
Service
Repair Commutator
8. Using a growler, test the armature for shorts.
• If the armature is shorted, then we recommend
that the armature or motor be replaced.
9. Using the continuity function of digital multi
meter, check the continuity around the entire
commutator by placing one test lead against one
of the commutator segments and the other test
lead against all of the other segments one at a
time. There should be continuity around the entire
commutator. If any segment indicates an open
circuit, then the motor must be replaced.
10. Using the continuity function of digital multi
meter, check the continuity from any one of the
commutator segments and the armature frame. If it
is not an open circuit, then the armature is shorted
and the motor must be replaced.
11. Measure the armature and field resistance (refer
Service Limits
to table at end of this section).
If the armature of field resistance is not within
specification then the motor must be repaired or
replaced.
Typical burn mark on a shorted armature
Motor Service
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