Resistances (Regulator); Temperature Compensation; Regulator Polarity; Regulator Maintenance - Piper PA-24 Comanche Service Manual

PIPER COMANCHE SERVICE MANUAL
winding is reduced, the spiral Sprinl tn.ion pulls the armature up, the cornact points close and
directly coanect the lenerator field to around. Output increa..s and the above cycle is repeated.
The cycle continues to take place while the current replator is in oper1ltion SO to 200 times a
second, preVtlfttinl the lenerator from exceedinl its rated maxim\llll. When the electrical I.oad is
reduced (electrical devic•• turned
oU
or battery cames up to cb.p), then the volta,e increases
so that the volta. reaulator belina to operate ad taptrs the lenerator output down. This
~ze.
vents the current replator from operatiaa. Either the volta. replatar or the current regulator
operates at anyone time-the two do not operata at the ...... time.
9-25. R.sistances. The current and voltap replatar circllitl use a common zesistor which is
inserted in the field cirellit when either the current or volta. Naulator operates. A second re-
sistor- is connected between the replator field tenninal Md the cutout relay frame. which places
it in paraUel with the gen.mor fiel.d coiia. The .udden reduction in field current occurring when
the current ar voltale re&Ulator contact point. open, i. accompanied by a lurle of induced volt.
ale in the field coils a. the Itrenath of the upetic field cban.... Th..e .urles are panial.ly
dissipated by the two resistors, thlla preVentml .xce••i.... areinl at the contact points.
-(The second resistor is not present on aU reCUI.tors. Many Aircraft regulators have this feSiStor
omitted. )
9-26. Tem,.,eture
C....
,.nnti... Volt..e replaters . . cocnpensated for temperature by means
of a bimetal thermostatic hiace on the armature. This cauan the replatar to regulate at a hilher
voltale when cold which partly cOlllpensat•• for the fact that I hiaher volta. is required to
charle a cold battery. Y1any current replators also have a bimetal thermostatic hinle on the
at·
mature. This permits a somewhat hiper .aerator output when the ullit i. cold. but causes the
output to drop off
u
temperature increa,es.
9-2i. R.,ulot. 'olerity.
Some NCUlators are desiped for use with neaalive Irounded
syste~s.
while other relulators are de.iifted far use with po,iUve Ifoullded systems. Using the wrong
polarity regulator on an installation will cause the zelulator contact points to pit badly and give
s hon \.ife. As a safeguard alainst illstallation
of
the wrOft' polarity felulator. all :egul.ators of
this type have the model number and the polarity c!early stamped on the end ofthe regulator ease ,
9-28. btulot. Maintenonce.
9-29. Generol 'nltructions.
a. Mechanical checks and Idjllstments (air .ap', point openin,) mUlt be made with battery
disconnected Ind reculator preferably off the aircraft.
CAUTION
The Cl,ltout rel.ay contact points must never
be
clOled by hand with
the battery connected to the replltor. Thi. would cause a high
current to flow throUlh the units which would seriollsly damage
them.
b. Electrical checks and adjustments may be made either on or off the airereft. The regulator
must always be operated with the type pnerator for which it is desilned.
ELECTRICAL
SYSTE:.I
ISSUED: 8/18/72
3
A23
•
•
•