CONSTRUCTION
AND
FUNCTION
terminal (N) - neutral point
of
the rectifier - and
ground. Terminal
(F)
is
for recehing field excita·
lion current from the lerminal (A)
of
the aller·
nator
unit
itself
oc.
at engine starting, from the
battery.
•.
Engine starting
With
the battery switch closed, lurning
on
the key
wilch
(by moving it
to
posilion I) allow, cunenl
A)~----------------------
--
--c
R.
to
flow
from the battery to the alternator field
and
also
to
the lamp. Field current al tltis
tim.
is
small because
of
resistor
RA
.
The
lamp bums to
teU
that
the alternator is not
generating
power.
TUnUng
the key switch
10
position 2 connect,
Iht
battery to Ihe slarter
10
crank the engine through
the
sequence
of
ac
ti
ons
alrudy
described.
'V\A
(,G))
-
"
on
.ltemtto
r
D
R
E)
! C R.
~
R,
I
~
.J
RMS4'2:i!7C9
N)
~--------------------------~
'"
P.
~s
£
i
~
!I
~
T
~
, =
I
~
_,
'I
Flow
of
current
for
starting
the
engine
42
Under
tItis
condition, pOinls
PI
,
p,
and
p,
remain
in
the indicaled state
by
their springs. Current
flow!
in
VC,
but it
is
too small to be
of
any
consequence.
b.
Nomlal charging operation
A. the engine starts up, the alternator unit
begins
to develop output voltage, so Ihal VC, becomes
energized (by the voltage between terminal (N)
and ground (E),
as
mentioned before) to opon
points
p,
and
put
out thelarnp.
The output current
of
the alternator unit flows
IlIIough
pOinl
P3
IOWaId
the
~auory
and toward
the alternator field through
pomts P, when the
output
vo
l
tage
is
up
at
the
nonnallenl.
If
Ihis voltage rises above the predetermined
level
,
the curreot
in
vel
increases to open points
PI
against its spring, so that field current
has
to
(Jow
through r.sistor
Rs
and is therefore smaller than
befor.: this reduces the output
voltase
of
the
alternator unit.
AClually, points P, open and close
in
rapid
succe5:jiion
to
regulate
the
volta
ge
at
a
relatiyeiy constant
leveL
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