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PART 13-4-ALTERNATOR REGULATOR
FIG. 28- Bosch Regulator
When the alternator voltage is
low the lower contacts will be closed
by the armature spring allowing full
system voltage to be applied to the
field windings.
Initial field excitation via the
ignition switch and indicator light
is applied to the field windings
through the lower contacts as resid-
ual magnetism in the alternator is
usually too small to start a voltage
build up.
2. Lower points open
-
first stage
of regulation Fig. 30.
When the alternator voltage
irn·
pressed on the electro-magnet reaches
a predetermined value the armature
is attracted to
the
core of the electro-
magnet, the lower contacts are opened
and a resistor is connected in series
with the field winding. The reduced
field strength causes the alternator
voltage to fall. As a consequence the
contacts cannot be held open
by
the
reduced influence of the electro-
magnet and they close. This cycle is
repeated 50-200 times per second
and the voltage is maintained at a
predetermined setting.
3. Upper contacts closed
-
field
circuit grounded
-
second stage of
regulation Fig. 31.
As the alternator speed and battery
voltage rise the voltage
begins
to
overcome the resistance and as a result
the alternator voltage will rise. The
influence of the electro-magnet be-
comes so strong that the upper points
will make
contact.
The stationary
upper point is grounded and so the
field circuit is short circuited. The
drop in voltage impressed on the
electro-magnet allows the armature
spring to open the upper points
and
the resistor is again in circuit, this
cycle of regulation on the
upper
points is also repeated many times
per
second.
OF TERMINAL
FIELD WINDING CIRCUIT
OF TERMINAL LAMP
INDICATOR LIGHT CIRCUIT
DF
TERMINAL
FOR
RADIO SUPPRESSOR
ALTERNATOR
IGN.
SWITCH
BATTERY
FIG. 29- Field Circuit- Lower Points Closed
ALTERNATOR
IGN.
SWITCH
BATTERY
FIG. 30- Field Circuit- Points Open
13-23
RESISTOR
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