PIPER
COMANCHE
SERVICE
MANUAL
9-61111.
Ret.lato.
(Pro.tolite).
~61n.
Ret.letar
C
...
pon
••
tl.
Alterlator
output volta
..
can.
",ithio the Umits
01
the
desi",
capability
of the
altemator.
be controlled by proporly vatylng the
avar.,_
level
of current flo",
in
the rotor
",indiog
.nd
the
PrestoUte
full
electronic
loUd
state
..
.wator
is
_II
luited
lor
this
purpose.
The
Preotolite
altemator.
due
to
its
design.
bas
.elf-limiti",
current
characteristics
and
needs
no current-limiting
unit
ill the
Nlulator.
I.
Transistor:
The
transistor
is
an
electronic
switch
wruch
can
turn OD and
twn
otf the flow
of
cumtnt
in
an
electric
circuit.
It
bu
no mechanical or
movinl
parts
to
wear
out.
b.
Rectifier
Diode: The
rectifier
diode
"'ill
pasl
current in one
direction
only (fo",·ard
direction);
and
in
this
respect.
it
may
be
compared to a ooe-
...
y
check
valw.
c.
Zener
Diode:
The
Zener
dinde.
in
addition
to
passi",
cuneltt
in the fo""ard
direction.
will
pass CUlmt1t
in
tbe
reverse
direction
only when a
particular
value
of
voltaae
is
applied
in
the
reverse
directioa.
It
is
this
Zener
action
whicb makes
it
adaptable
for lise
as
a voltage
senaina
device
in
the
reaulator.
d.
Resistor:
The
ralStar
is
a
device
whicb
is
aed.
to
limit
current
flow.
9-610.
O~.ration
Of
Ret.lotar.
(Refer to
Figure
9-27p.)
a.
When
the
alternator
switch
is
twned
on. battery
voltage
is
ap~lied
to the
"I"
terminal of
the
regulator.
b.
The
"I'n
(negative-poeitive-necatiw)
po1"er
transistor.
T3. is
twned
on
by
CUtTent
flow
from
the
ignillon
terminal through
R6
and the
collector
emitter
junction
01
T2 'hrouCh
02
throulh
the
base
emitter
junction of
T3
to
I'ound.
c.
Whenever the power
transistor.
T3.
is
on tT2
is
also
CD
and
T1
is off). current
"ill
flow
from
the
ignitl0n
tenlUnal
throulh
the field
"inding.
throuCb the
collector
•
eautter
of T3
to
ground.
d. With
the
ignition
switch
on,
current
will
flow
{rom
the'
II"
terminal
regulator
ground through
a
voltage
diViding network consistin.g of R1. R2 and
Pi.
This
network determines the
system
operating
voltage
relative
to
the
Zener
diode.
Zl.
reverse
conduct
ina
voltage.
e. When the
system
voltate
connected to
"I"
termiaal
reaches a value
at
which the Zener
diode
connected
to
the
divider network
conducts.
cwrent
will
flow
from
the
"I"
termInal through
R1
through Z1 and tbrough
tbe
base
emitter
junction
01
T1 to ground.
This
causes
the
collector
emitter
junctlon
of
Tl
to
conduct
which
diverts
the
bale
cunent
of T2 flOWing
from
"1"
terminal
throulh
R4
to ground. turning off T2 which turns off T3.
de
....
nerCizing the rotor winding; then.
when the
alternator
output vo1tace falls to a
value
which permits
Zt
to cease coruiuction,
Tl
will
turn off
.,luch
turns
on
T2 and T3
.....
nerctZi",
the rotor winding.
f.
This
sequence
is
performed.
so
rapIdly
that
the rotor currel'lt
average
appears
as
a value
usually
less
than
fuji
rotor
cwrent
depending
on rotor RP'II and
system
load
connected.
,.
Each
time the power
transistor.
T3. is turned off. current
flow
in the rotor Winding
15
reduced..
This
causes
the rotor maanetic field to
collapse
which would
lenerate
hIgh
voltage
at
the
power
transIstor.
T3.
if
a path were
not
provu:1ed
so
that
the
held
current can
decay
at
a
slower
rate.
The
field
suppression
diode.
01.
provtdes
this
path.
thu.s
protectll'll
the
system
and
relWator
lrom
possible
dalllOge.
h.
Tempera~ure
compensation is
nat
which
!Deans
the regulator will hold the
alternator
out·
put voltage
constant
with temperature
increase
or
decrease
after irutial warm-up.
i.
The
Prestolite
solid
state
regulator
uses
three npn
silicon
transistors.
ELECTRICAL
SYS-:-EM
ISSUED:
8/18172
3
C6
•
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