 |
|||
|
|
|||
|
|
|||
| ||||||||||
|
|
 d.
Remove the commutator end frame
by bending wire slightly and reinsulating
(Item 28) and field frame assembly
exposed bare wire.
If short cannot be
It may be necessary to tap
eliminated, armature must be replaced.
(Item 3).
the end frames with a fibre hammer to
remove them from the motor frame.
Test for open circuits.
STEP 2.
Remove the solenoid (Item 9) and
e.
Open circuits in an armature may
a.
shift
lever assembly (Item 6) from the
be caused by a poor connection of leads
drive
housing, them remove the armature
in the commutator bars or by a broken
Either will
(Item
14) from the drive housing.
wire in a armature coil.
Poor
cause sparking at the brushes.
Remove the thrust collar (Item 11)
connections and broken wires can often
f.
When this is
from the armature shaft.
be detected visually.
test for open circuits
not possible,
Remove the pinion (Item 13) from
as follows:
g.
the armature; by sliding a metal cyl-
Set up the armature
inder onto the shaft; with a hammer
Growler Test.
b.
striking the metal cylinder against the
on the growler as shown in figure 5-71.
retainer, drive the retainer toward the
Test the top two adjacent bars with an
Rotate the armature
armature core and off the snap ring.
AC Millivoltmeter.
When
and continue testing adjacent bars.
Remove the snap ring (Item 12)
the millvoltmeter bridges the two bars
h.
connected to the open coil, the meter
from the groove in the armature shaft.
All other
pointer will not be deflected.
Remove the motor drive clutch
bars will give a deflection.
1.
(Item 15). Roller type clutches are
Bar-to-meter test.
STEP 3.
designed to be serviced as a complete
(Figure 5-72).
unit, therefore DO NOT disassemble.
Replace if necessary.
This method of finding an open
a.
Clean all parts with a Stoddard
coil is more satisfactory and reliable
j.
type solvent and inspect carefully
than the growlermeter test and is often
used in preference to it.
for conditions of wear or damage. The
following tests will help to locate
Place the armature in "V" blocks
electrical faults in the components.
b.
and connect a source of direct current
ARMATURE TESTS.
to the commutator, using the circuit
5-56.
of figure 5-72.
Test for shorts (Figure 5-71)
STEP 1.
c.
Test by spanning bar with Milli-
Check armature for shorts by
voltmeter leads.
a.
placing it on a "growler" and with
The meter will not show a reading
a steel strip or hack-saw blade
d.
until it bridges bars 6 and 7 as an
held on armature core, rotate
The meter
example shown in figure 5-72.
If blade vibrates, arma-
armature.
completes the circuit.
ture is shorted in an area of the
coare below the vibrating blade.
b.
Cooper or brush dust in slots
between commutator bars sometimes
cause shorts which can be eliminated
5-45
|
|
Privacy Statement - Press Release - Copyright Information. - Contact Us |
Click
here for thousands of PDF manuals