Ford Corsar Repair Manual page 835

CHARGING SYSTEM -Alternator-
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ALTERNATOR
B O S C ~ K1 -80
DESCRIPTION
The 3 phase BOSCH alternator is a
12 pole machine equipped with silicon
diodes for rectification and a built-in
electronic regulator. Cooling is by an
external fan located behind the pulley.
The six diodes are arranged in a 3 phase
bridge connection whereby 3 diodes
have anodes at the connection (normal
polarity) and 3 diodes have anodes at
the housing (reverse polarity). See
Figure 2.
The alternator is designed for nega-
tive ground operation. When an indica-
tor lamp is used in the system a
further 3 smaller diodes are fitted into
the rectifier assembly.
The stntor winding has
: I
star connec-
tion
-
see Figure
i -
with three outlets
which are connected to the rectifier as-
sembly.
The rotor comprises the slip rings
and exciter winding and is constructed
of imbricated poles which form alter-
nator north and south poles. The
exciter winding is wound concentric
with the shaft inside the claw poles
and has its ends connected t o the slip
rings.
SUPPRC SSOR
r - - - -
I
- - - - - -
I
l
I
I
0, REGULATOR
I
1
OF
1
l
I
I
X09 1
Fig. I . 9-diode alternator with built-in regulator
C o n n e c t ~ o n
Current
(Anode) Housing (Anode)
Current flow
ked
<
I
; * l
D ~ o d e
Housing (Cathode) Connection ( ~ a i h o d e )
X 0 9 2
Fig. .? Dioclc, c.or~nrc.tiot~.c-
ALTERNATOR
OPERATION
(See Figure
1
for wiring diagram.)
When the ignition switch is turned
to the
'ON' position, battery current is
supplied to the exciter winding
through the warning lamp. If we look
Bt one pair of rotor poles, it will be
seen that the magnetic field of the
rotor will be broken by one loop of
the stator winding as the rotor is
turned.
A
voltage will be induced in t h s
conductor and because of the closed
circuit a current will flow away from
the wire connection through a phase
winding. Since the phase is connected
t o both a positive and a negative
diode, the current will flow thorugh
the positive diode, which is open to
current flow in this direction. The,
negative diode of this phase obstructs
current flow. From the positive diode
the current passes into the heat sink,
which is conimon t o the
B+
terminal,
and then t o the battery.