Short-Circuited Armature Or Field Winding; Grounded Motor Test - Toyota 7BPUE15 Service Manual

Section 5. Troubleshooting
Electric Motor Tests
3. Y
O U
measurements:
Drive Motor
(shunt)
A2
Lift Motor
A to Frame
Steer Motor
4. If the meter indicates high resistance in
the armature, check the condition of the
brushes before replacing the motor.
5. If you find a n open circuit in a
series-wound motor, the motor must be
disassembled by a motor rebuilding facility
to isolate the problem to the field or
armature circuit.

Grounded Motor Test

In a grounded motor, a n electrical circuit exists
between the current-carrying conductors and
the motor housing. This can be caused either by
direct contact or through conductive foreign
material.
The ground may be caused by:
Insulation breakdown
Brush leads touching the motor housing
Buildup of carbon dust or other materials
To test for a grounded motor, see "Shorts to
Frame Test" on page 5-4.
0.9 to 1.5
o h m s
100,000
o h m s
100,000
100,000
Frame
100,000
Frame
Toyota Orderpicker Model 7BPUE 15 Service Manual
Short-circuited Armature or
Field Winding
insulation on the field o ; armature has broken
down a t two or more points. The breakdown
creates a low resistance path, allowing 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
total resistance of the motor winding and a n
increase in the current flow. The severity of the
short circuit depends on its location.
shorted motor may be indicated by:
A
Slow or sluggish operation
Running faster than normal (suggests a
short in the field)
Overheating
Blowing a power fuse
Burning of brush wires
Severe burning or discoloration on
armature coil
Severe burning or discoloration on one or
two commutator segments every 90" of
rotation.
These symptoms can be caused by problems
other than the motor itself:
Brake too tight or dragging
Wheel bearings too tight
Faulty transmission
Binding in a related pump, hose, or
solenoid valve
Load wheels not aligned properly
Rail guided with drive tire not aligned
properly
Testing a motor for short-circuited windings
requires special equipment a t a motor
00700-CL222-05, 1 5 March 2005
is