Specifications

171
Table 15.2 Trouble Shooting chart - D.C. Machines
S. No Symptom Possible Cause of
Trouble
Remedy
1 Failure to build up of
voltage (dc generator)
Output voltage too low
(dc generator)
Faulty Voltmeter, check
output voltage with separate
voltmeter. Open field
resistor.
Open field circuit. Check
coils for open circuit or
loose connections.
Absence of residual
magnetism in self excited
generator.
Dirty commutator, high
mica, brushes not having
good contact with
commutator.
New brushes seated but not
contacting sufficient area.
Armature shorted internally
to ground.
Replace voltmeter. Replace
or repair resistor
Replace defective coils,
tighten or solder loose
connections.
Flash the field. Connect
battery to field with correct
polarity Allow current
momentarily and cut off.
Field will resume residual
magnetism.
Under cut mica, clean or
dress commutator.
Replace or reseat brushes,
free if binding in holders.
Brush bedding and reseat
brushes. Remove, test and
repair or replace.
Grounded or shorted field
coil.Shorted filtering
capacitor; open filter choke,
open ammeter shunt,
broken brush shunts.
Prime mover speed
low(check speed)
Brushes not seated
properly.Commutator dirty,
or film too heavy
2 Test, repair or replace.
Adjust governor on prime
mover. Reseat brushes.
Clean commutator with fine
sand paper. Replace
brushes with proper grade
set or Use complete new
set of brushes
Adjust properly. Connect
properly