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 TM 5-683/NAVFAC MO-116/AFJMAN 32-1083
Table 4-5. DC motor or generator trouble-shooting.
Maintenance
Trouble
Probable Cause
Check control for open in starting
Motor will not
Open circuit in
c i r c u i t , open contacts, fuse or
start.
control.
breaker.
Check voltage with nameplate
Low terminal voltage.
rating.
Recondition
shaft and replace
Bearing frozen.
bearing.
Reduce load or use larger motor.
Overload.
Check
lubricaton
in bearings to
Excessive
make sure that the oil has been
replaced after installing motor.
Disconnect motor from driven
machine, and turn rotor by hand to
s e e if trouble i s i n m o t o r .
Strip and reassemble motor; then
check part by part for proper
location and fit.
S t r a i g h t e n or replace bent or
spring shaft (machines under 5
hp).
springs, need
Held up by brush
Brushes not down on
commtator.
replacement.
Replace brushes.
Brushes worn out.
Remove and sand,
clean up brush
Brushes stuck in
boxes.
holders.
Power may be off.
Check line connectons to starter
with light.
Check contacts in starter.
Check generating unit
for
cause
of
Reverse polarity of
Motor starts, then
changing polarity.
generator that
stops and reverses
supplies power.
direction of
rotation.
Shunt and series
Reconnect either the shunt or
fields are bucking
series field in order to correct
each other.
the polarity.
Then connect
armature leads for desired
The fields
direction of rotation.
can be tried separately to
determine the direction of
rotation
individually
and
connected so that both give same
rotation.
4-36
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