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Figure 2-39.—Typical overrunning clutch. | Up
Construction Mechanic Basic Volume 02 - Construction methods and practices | Next
Neutral Safety Switch |
The starter solenoid may be located away from or
on the starting motor. When mounted away from the
starter, the solenoid only makes and breaks electrical
connection. When mounted on the starter, it also slides
the pinion gear into the flywheel.
In operation, the solenoid is actuated when the
ignition switch is turned or when the starter button is
depressed. The action causes current to flow through
the solenoid (causing a magnetic attraction of the
plunger) to ground. The movement of the plunger
causes the shift lever to engage the pinion with the ring
gear. After the pinion is engaged, further travel of the
plunger causes the contacts inside the solenoid to close
and directly connects the battery to the starter.
If cranking continues after the control circuit is
broken, it is most likely to be caused by either shorted
solenoid windings or by binding of the plunger in the
solenoid. Low voltage from the battery is often the
cause of the starter making a clicking sound. When this
occurs, check all starting circuit connections for
cleanliness and tightness.
FIELD FRAME.—The field frame is the center
housing that holds the field coils and pole shoes.
The field coil (winding) is a stationary set of
windings that creates a strong magnetic field around
the motor armature. When current flows through the
winding, the magnetic field between the pole shoes
becomes very large. Acting against the magnetic field
created by the armature, this action spins the motor
with extra power. Field windings vary according to the
application of the starter motor. The most popular
configurations are as follows (fig. 2-41):
TWO WINDINGS, PARALLEL—The wiring
of the two field coils in parallel will increase
their strength because they receive full voltage.
Note that two additional pole shoes are used.
Though they have no windings, their presence
will further strengthen the magnetic field.
FOUR WINDINGS, SERIES-PARALLEL—
The wiring of four field coils in a series-parallel
combination creates a stronger magnetic field
than the two field coil configuration.
FOUR WINDINGS, SERIES—The wiring of
four field coils in series provides a large amount
of low-speed torque, which is desirable for
automotive starting motors. However, series-
wound motors can build up excessive speed if
Figure 2-41.—Field winding configurations.
2-28
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