Regulator Components; Regulator Overhaul - Piper PA-24 Comanche Service Manual

PIPER COMANCHE SERVICE MANUAL
9-61n. Retulotor Com,.ne"t•• Alternator output voltap
~an.
within the limits of the desien
capability of the alternator. be controlled by properly varyiq the averale level of currant fiow
in the rotor windinl and tht Pt..toUte full electronic lolid Itate repl.tor
is ...
11 suited for this
purpo...
The
Pr.toUte alternator. due to its desiln. bas lelf..lilllitiftl current characteristics
and needs no cunent..limitinl IUlit
in
the replator.
a. Transistor: The transistor is an electronic ,witch which can turn on and turn od the flow
of current in an electric circuit. It hallO mechanical or lDOvilli pens to we.r out.
b. Rectifier Diode:
The
rectifier diode will
pal am_at
in
one
direction only (forward
direction); and in this respect. it mey
be
compared to.
cae·..
y check valva.
c. Zener Diode:
The
Zener diode.
ill
addition to ,...iftl cunent in the forward direction.
will pass current in the reverse dilWCtion only when a particular val .... of volta..
is
applied in
the reverse direction. It is this Zener action whicb _ke.
it
adaptable for use as a voltace
sensinl device in the recwator.
d. Resistor: The resistor is a device which i. l15ed to limit current now.
9-610. Operation
Of
Rot.letor. (Refer to
F
iCure 9·27p.)
a. When the alternator switc::h is turned on. attery voltap is .pplied to the
"I"
tetrllinal of
the relulator.
b. The npn (IWlative.poaitive.cwcative) porer trallli.tor.
T3.
i. turned on by cumtnt flow
from the ianition terminal tbrouah R6 and the collector emitter jWlCtion of T2 throuCh 02 thtoulh
the base emitter junction of T3 to &found.
c. Whenever the power tranai.tor. T3. i. on (T2 is also on aad T1 is off). current will flow
from the ilnition tetrllinal tbrouCh the field winclinl. thtoulh the collector • emitter of T3 to
cround.
d. With the ignition switch on. current will
flow
from the •
'ttl
termin.l rel'llator Cround throush
a voltage dividinc network cOMistinl of R1. R2 aad Pl.
nul
network determines the system
operatinc voltale relative to the Zener diode. Zl. reverse conduetiftl volta...
e. Whe:\ the system voltap connected to
"t"
terminal eache. a value at which the Zener
diode connected to the divider network conducts. current will
now
from the "I" teruunal through
R1 through Z1 and throuah
tt.
bue emitter junction of T1 to &found. This causes the collector
emmer junction of T1 to conduct which diverts the ba.e cunent of T2 flowinl from "I" termInal
throuch R4 to cround, turninc off T2 which tums off T3.
de~nerlizinc
the rotor wincline; :hen.
when the alternator output voltale falb to a value which perlllits Zl to cease conduction. T1 will
turn off which turns on T2 and T3. re4nerCizinc the rotor windine.
f. This sequence
is
performed so rapidly that the rotor curNnt avera.e appears as a value
usually Less than fwl rotor current dependinc on rotor RPM and system load connected.
a. Each time the power transistor. T3.
is
turned off. current fiow in the rotor windina
is
redl,lced. This causes the rotor macnetic field to collapse whieh would aenerate hiCh voltage
at
the power transistor. T3. if a path were not prOVided so that the field current can decay at a
slower rate. The field suppression diode. 01. prOVides this path. thus protecting the system and
regulator from possible damace.
h.
Tempera~ure
compen.ation is flat which means the reculator will hold the alternator out-
Pl,lt voltage constant with temperature inczease or decr•••• after initial warm..up.
i . The Prestolite solid stat. relulator uses three npn silicon transistors.
ELECTRICAL
SYS~EM
ISSUED: 8/18/72
3 C6
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