Model 8210/8250 Maintenance Manual Section 5. Troubleshooting
DC Electric Motors
Publication:1146945/001, Revised: 25 Sep 2018 5-13
Short-Circuited Winding
A short-circuited winding is one where the
insulation on the field or armature has broken
down at two or more points. The breakdown
creates a low resistance path, permitting
current to flow from one turn of the coil to
another adjacent coil turn, without actually
flowing through the coil wire. The result is a
decrease in the total resistance of the motor
winding and an increase in the current flow.
The severity of the short circuit depends on its
location.
A shorted motor may be indicated by:
• Slow or sluggish operation
• Running faster than normal
•Overheating
• Blowing a power fuse
• On DC motors, severe burning or
discoloring on one or two commutator
segments every 90° of rotation
These symptoms can also be caused by
problems other than the motor itself, such as:
• Brake too tight or dragging
• Wheel bearings too tight
• Faulty transmission
• Binding in an attached pump
Testing a motor for short-circuited windings
requires special equipment at a motor
rebuilding facility.
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