TP-6519 8/1754 Section 5 Component Testing and Adjustment
5.5 Slip Rings
Slip rings acquire a glossy brown finish in normal
operation. Do not attempt to maintain a bright,
newly-machined appearance on the slip rings.
Cleaning with a dry, lint-free cloth is usually sufficient.
Use very fine sandpaper (#00) and apply light pressure
to remove roughness. Do not use emery or
carborundum paper or cloth. Clean all c arbon dust from
the generator after sanding the s lip rings. If the rings are
black or pitted, remove the r otor and use a lathe to
remove some of the slip ring surface material.
5.6 Brushes
The brushes transfer current from the SCR module to
the slip rings. The brushes should last the life of the
generator. However, abrasive dust on the slip rings
shortens the life of the brushes.
Excessive arcing at the brushes could damage the SCR
module and the controller. Weak springs, damaged slip
rings, sticking brushes, a loose brush holder, or poor
brush contact causes arcing.
The brushes must be free to move within the holder and
be held in contact with the slip rings by the springs.
When correctly positioned, spring pressure on the
brush surface causes the brush to wear evenly. The
entire brush must ride on the ring or arcing occurs and
causes burned rings or voltage regulator failure.
Figure 5-10 shows the correct positioning of the
brushes. Add or remove shims as necessary to center
the brushes on the slip rings. Replace the brushes if
they show uneven wear or are worn to one half their
original length.
Check the resistance through the brushes. Resistance
through the brushes should be low, 0.1-- 0.2 ohms
without meter lead resistance.
TP5867
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Front View
Side View
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New 1.9 cm (0.75 in.)
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1. Brush holder
2. Slip ring
3. Brush(es)
4. Retainer wire
5. Shim
6. Spring
7. Correctly positioned brush
8. Incorrectly positioned brush
GM29253B-P
Figure 5-10 Brush Assembly
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