Faults and remedies
Electrical
Fault
Possible cause
Remedy
Motor will not start at no load
No armature voltage
Check supply
Armature coils burnt out or short-
circuited
Clear short-circuit (generally
only possible in specialist’s or
manufacturer’s workshop)
Brushes not making proper contact
Check pressure and position of
brushes, replace worn brushes
No excitation voltage
Check supply
Open circuit in field winding
Remedy open circuit
Interturn short-circuit in the armature
winding
Repair in workshop
Short-circuit between commutator
segments
Check commutator and eliminate short
Motor will not accept load
Overload
Check current input and eliminate
overload
Voltage decreasing
Check supply
Motor overspeeding and hunting
under load
Brushes displaced from neutral zone in
opposite direction to rotation position
Set brush-bracket to mark under load
Fault in field circuit
Eliminate fault
Auxiliary series winding wrongly
connected
Check connection and correct
Generator not supplying voltage
Open circuit in excitation circuit
Check excitation circuit for fault
Short in main circuit
Check circuit
Open circuit or interturn short-circuit in
rotor winding
Check winding for open circuit or
interturn short-circuit
Voltage drop on unregulated
generator on load is too high
Speed reduction of drive too great
Set drive to normal speed, drive too
weak
Incorrect brush setting
Check brush setting, correct
Overheating in operation
Overload
Check voltage and current, eliminate
overload
Insufficient cooling air
Improve cooling
Temperature of cooling air or water too
high
Clean internal and external air
passages
Insufficient cooling water
Check flow rate of cooling water,
increase if necessary
Cooler or filter dirty
Clean cooler, change filter
