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(b)Diameter of commutator
Measure the diameter of commutator.
If it exceeds the limit, replace the armature.
Unit: mm (in.)
Item Standard Limit
Diameter of 32(1.26) 31(1.22)
commutator
(c)Mica undercut
Measure the undercut of mica insulation
between the adjacent segments. If
undercut exceeds the limit, recondition
the mica, or replace the armature.
Unit: mm (in.)
Item Standard Limit
Undercut 0.5 (0.020) 0.2 (0.008)
of mica
(d)Testing for short circuit
Place the armature on growler and
slowly rotate it with a hacksaw blade
held above the armature core. The
hacksaw blade vibrates against the core
when it is above a slot containing a
shorted winding. A shorted armature
should be replaced.
(e)Testing for grounded circuit
Test the armature for grounded circuit as
shown in the illustration. If there is any
continuity between commutator segment
and coil, the armature is grounded and
should be replaced.
(f)Testing for open circuit
Test the armature for open circuit as
shown in the illustration. If there no
continuity between the segments, the
armature is open circuited and should be
replace.
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