REFLECTOR:Alternator wiring

Laurence Coen reflector@tvbf.org
Thu, 1 May 2003 12:06:32 -0500


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Hiroo,

The "S" connection is the "Sense" or field reference. When connected to =
the buss it automatically compensates for any voltage drop in the =
alternator power wire.  The "L" is the "Light" connection and is for the =
so called idiot light output.  This configuration comes from the =
automotive world.  On an auto the + or "Bat" terminal is connected =
directly to the battery and is not switched.  When the ignition is =
turned on , power is applied to the sense lead which causes the "idiot =
light" to come on.  When the engine starts and the alternator begins to =
produce power the "idiot light" goes out.  The primary reason that =
aircraft have over voltage protection and cars don't is the master relay =
or solenoid.  On a car the battery provides over voltage protection =
since it is always connected to the alternator.  Airplanes can isolate =
the battery by turning off the master with the engine still running and =
the alternator still connected to the aircraft buss.  Under these =
conditions it is likely you will get an over voltage surge and maybe =
smoke some expensive stuff on your panel if you don't have over voltage =
protection.
I hope this is helpful and doesn't simply add to the confusion.

Larry Coen
SE RG Franklin
  ----- Original Message -----=20
  From: Hiroo Umeno=20
  To: reflector@tvbf.org=20
  Sent: Tuesday, April 29, 2003 3:19 PM
  Subject: REFLECTOR:Alternator wiring


  Here I am, still doing wiring.



  My alternator I got from Franklin guys in CO got me scratching my =
head.  Many of the airplane wiring references refer to three major =
connections to the alternator.  Airframe GND, Alternator Field, and =
Alternator Out.



  Now, as I look at my alternator, there appears to be four connections. =
 One is the GND which essentially is the casing bolted down to the =
engine.  Then there is a terminal that is marked with '+' symbol that I =
figured is the OUT judging from the size of the bolt and nut on the =
terminal.  Now, on the side, there is a plastic connector that has two, =
yes two, wires coming out.  One is yellow and the other is green.  They =
are marked 'S' and 'L'.  I am guessing one of them is the 'Field' but =
which one?



  Has anyone got this figured out?



  Hiroo


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<BODY lang=3DEN-US vLink=3Dpurple link=3Dblue bgColor=3D#ffffff>
<DIV><FONT face=3DArial size=3D2>Hiroo,</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>The "S" connection is the "Sense" or =
field=20
reference. When connected to the buss it automatically compensates for =
any=20
voltage drop in the alternator power wire.&nbsp; The "L" is the "Light"=20
connection and is for the so called idiot light output.&nbsp; This =
configuration=20
comes from the automotive world.&nbsp; On an auto the + or "Bat" =
terminal is=20
connected directly to the battery and is not switched.&nbsp; When the =
ignition=20
is turned on , power is applied to the sense lead which causes the =
"idiot light"=20
to come on.&nbsp; When the engine starts and the alternator begins to =
produce=20
power the "idiot light" goes out.&nbsp; The primary reason that aircraft =
have=20
over voltage protection and cars don't is the master relay or =
solenoid.&nbsp; On=20
a car the battery provides over voltage protection since it is always =
connected=20
to the alternator.&nbsp; Airplanes can isolate the battery by turning =
off the=20
master with the engine still running and the alternator still connected =
to the=20
aircraft buss.&nbsp; Under these conditions it is likely you will get an =
over=20
voltage surge and maybe smoke some expensive stuff on your panel if you =
don't=20
have over voltage protection.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>I hope this is helpful and doesn't =
simply add to=20
the confusion.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>Larry Coen</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>SE RG Franklin</FONT></DIV>
<BLOCKQUOTE dir=3Dltr=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
  <DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
  <DIV=20
  style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
  <A title=3Dhumeno@microsoft.com =
href=3D"mailto:humeno@microsoft.com">Hiroo=20
  Umeno</A> </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Dreflector@tvbf.org=20
  href=3D"mailto:reflector@tvbf.org">reflector@tvbf.org</A> </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Tuesday, April 29, 2003 =
3:19=20
  PM</DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Subject:</B> REFLECTOR:Alternator=20
wiring</DIV>
  <DIV><BR></DIV>
  <DIV class=3DSection1>
  <P class=3DMsoNormal><FONT face=3DArial size=3D2><SPAN=20
  style=3D"FONT-SIZE: 10pt; FONT-FAMILY: Arial">Here I am, still doing=20
  wiring=85</SPAN></FONT></P>
  <P class=3DMsoNormal><FONT face=3DArial size=3D2><SPAN=20
  style=3D"FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN></FONT>&nbsp;</P>
  <P class=3DMsoNormal><FONT face=3DArial size=3D2><SPAN=20
  style=3D"FONT-SIZE: 10pt; FONT-FAMILY: Arial">My alternator I got from =

  </SPAN></FONT><FONT face=3DArial size=3D2><SPAN=20
  style=3D"FONT-SIZE: 10pt; FONT-FAMILY: =
Arial">Franklin</SPAN></FONT><FONT=20
  face=3DArial size=3D2><SPAN style=3D"FONT-SIZE: 10pt; FONT-FAMILY: =
Arial"> guys in=20
  CO got me scratching my head.&nbsp; Many of the airplane wiring =
references=20
  refer to three major connections to the alternator. &nbsp;Airframe =
GND,=20
  Alternator Field, and Alternator Out.</SPAN></FONT></P>
  <P class=3DMsoNormal><FONT face=3DArial size=3D2><SPAN=20
  style=3D"FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN></FONT>&nbsp;</P>
  <P class=3DMsoNormal><FONT face=3DArial size=3D2><SPAN=20
  style=3D"FONT-SIZE: 10pt; FONT-FAMILY: Arial">Now, as I look at my =
alternator,=20
  there appears to be four connections.&nbsp; One is the GND which =
essentially=20
  is the casing bolted down to the engine.&nbsp; Then there is a =
terminal that=20
  is marked with =91+=92 symbol that I figured is the OUT judging from =
the size of=20
  the bolt and nut on the terminal.&nbsp; Now, on the side, there is a =
plastic=20
  connector that has two, yes two, wires coming out.&nbsp; One is yellow =
and the=20
  other is green.&nbsp; They are marked =91S=92 and =91L=92.&nbsp; I am =
guessing one of=20
  them is the =91Field=92 but which one?</SPAN></FONT></P>
  <P class=3DMsoNormal><FONT face=3DArial size=3D2><SPAN=20
  style=3D"FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN></FONT>&nbsp;</P>
  <P class=3DMsoNormal><FONT face=3DArial size=3D2><SPAN=20
  style=3D"FONT-SIZE: 10pt; FONT-FAMILY: Arial">Has anyone got this =
figured=20
  out?</SPAN></FONT></P>
  <P class=3DMsoNormal><FONT face=3DArial size=3D2><SPAN=20
  style=3D"FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN></FONT>&nbsp;</P>
  <P class=3DMsoNormal><FONT face=3DArial size=3D2><SPAN=20
  style=3D"FONT-SIZE: 10pt; FONT-FAMILY: =
Arial">Hiroo</SPAN></FONT></P></DIV></BLOCKQUOTE></BODY></HTML>

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