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mchamberlain(at)runbox.co
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 Posted: Mon May 22, 2006 6:25 pm Post subject: Alternator Field Breaker/Switch |
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Hi All,
I'm just in the process of designing the electrical system for my RV-7
and I'm trying to figure out why we need a field switch and/or breaker
for the alternator? I've searched and searched, I can find lot's of
information on how to wire it, but as to the questions "why?", or what
does the "field" wire do ; I can find nothing. I'm guessing it is a very
simple answer and it is just my inexperience showing through.
If someone could enlighten me it would be much appreciated.
Thanks,
Mark
RV-7 - Panel
DO NOT ARCHIVE
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Dale Ensing
Joined: 11 Jan 2006
Posts: 571
Location: Aero Plantation Weddington NC
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| Posted: Mon May 22, 2006 7:25 pm Post subject: Alternator Field Breaker/Switch |
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|
I'm just in the process of designing the electrical system for my RV-7
and I'm trying to figure out why we need a field switch and/or breaker
for the alternator? I've searched and searched, I can find lot's of
information on how to wire it, but as to the questions "why?", or what
does the "field" wire do ; I can find nothing. I'm guessing it is a very
simple answer and it is just my inexperience showing
In simple terms.........
The field switch supplies current to the alternator field which is required
for the alt. to produce electricity.
The breaker the field switch draws current from is to protect the wiring in
case of an excessive current such as a short.
Dale Ensing
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_________________
Dale Ensing
RV-6A
Aero Plantation
Weddington NC |
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Dan.Beadle(at)hq.inclines
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| Posted: Tue May 23, 2006 6:13 am Post subject: Alternator Field Breaker/Switch |
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Think of the alternator as having leverage: you put a little current
into the alternator to get a lot out. Kind of like an amplifier. (Of
course, there is no free lunch - the power for the leverage comes from
the engine a HP load).
The Field switch lets you turn off the demand for power from the
alternator.
WHY would this be important? Suppose you have an electrical fire and
you need to turn off all power to the busses - the field switch is the
key.
Dan
--
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brian
Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA
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| Posted: Tue May 23, 2006 8:12 am Post subject: Alternator Field Breaker/Switch |
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|
On May 22, 2006, at 7:19 PM, Mark Chamberlain wrote:
| Quote: | information on how to wire it, but as to the questions "why?", or what
does the "field" wire do ; I can find nothing. I'm guessing it is a
very
simple answer and it is just my inexperience showing through.
|
If you go back to an elementary science class, someone once told you
that if you wave a magnet around a wire, that wire will produce an
electric current. They also probably told you that if you pass a
current through a wire it will produce a magnetic field around the
wire. This was the amazing discovery of Michael Faraday and upon
which all electrical and radio theory is based.
Some alternators or generators do indeed use a permanent magnet
whirling around inside a coil of wire to produce power but the output
is directly proportional to how fast you spin it. If it makes more
output than you need you must find a way to get rid of the excess.
This is not a problem if the output is relatively small but if you
want something that can produce a lot of output for the times when
you need a lot of output, it produces way too much when you don't
need it all. Hence permanent magnet alternators, officially known as
"dynamos", tend to be small things.
But if you want one that can produce a lot of output when needed but
not much output when not needed you need a way to vary the
effectiveness. If you remember the two things that our buddy Mike
discovered, i.e. that moving magnetism generates an electric current
and moving electrons generate magnetism, you have the basic
components you need. If you want to increase the output of your
alternator at a given rotational velocity you need more magntism and
vice versa. So how can we turn the magnatism up and down as needed?
Why, we use a coil of wire with a current flowing through it. If we
increase the current, the magnetism increases and the output of our
alternator increases. If we reduce the current, the output of our
alternator decreases. This electromagnet is the rotating part of the
alternator. It is called the rotor but it is also called the field
winding from the olden days when we used generators.
A generator has the power-producing windings on the spinning part
called the armature and the magnetic field producing part, the field
windings, around the outside. An alternator has the magnetic field
windings on the spinning part (rotor) and the power-producing coils
(stator) are around the outside. You see I keep using the term
"magnetic field producing part" over again. That just got shortened
over time to the word "field".
So the way this whole thing works is to have an external sensor
determine if the alternator is producing as much power as needed. It
does this by measuring the voltage on the bus. If the voltage is too
low it allows more current to flow through the field winding. This
increases the magnetism in the center of the alternator and that then
induces more output in the stator winding. The voltage rises. If the
voltage gets higher than we want the VR reduces the current in the
field, the magnetic field is decreased, the output of the stator
windings is less, and the voltage at output is reduced. To me this
represents PFM (Pure f'n magic) and is also PFN (pretty f'n neat).
Thanks Mike!
Brian Lloyd 361 Catterline Way
brian-yak AT lloyd DOT com Folsom, CA 95630
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
Antoine de Saint-Exupry
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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_________________
Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery |
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rv8ch
Joined: 10 Jan 2006
Posts: 250
Location: Switzerland
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| Posted: Tue May 23, 2006 9:52 am Post subject: Alternator Field Breaker/Switch |
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> ...
| Quote: | So the way this whole thing works is to have an external sensor
determine if the alternator is producing as much power as needed. It
does this by measuring the voltage on the bus. If the voltage is too
low it allows more current to flow through the field winding. This
increases the magnetism in the center of the alternator and that then
induces more output in the stator winding. The voltage rises. If the
voltage gets higher than we want the VR reduces the current in the
field, the magnetic field is decreased, the output of the stator
windings is less, and the voltage at output is reduced. To me this
represents PFM (Pure f'n magic) and is also PFN (pretty f'n neat).
Thanks Mike!
|
Couldn't agree more. BTW, thanks for a most excellent description
of how this works, Brian!
--
Mickey Coggins
http://www.rv8.ch/
#82007 finishing
do not archive
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_________________
Mickey Coggins
http://www.rv8.ch/ |
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n801bh(at)netzero.com
Guest
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| Posted: Tue May 23, 2006 4:04 pm Post subject: Alternator Field Breaker/Switch |
|
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VERY WELL PUT !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
this needs to be archived too...
Ben Haas
N801BH
www.haaspowerair.com
-- Brian Lloyd <brian-yak(at)lloyd.com> wrote:
m>
On May 22, 2006, at 7:19 PM, Mark Chamberlain wrote:
| Quote: | information on how to wire it, but as to the questions "why?", or what
|
| Quote: | does the "field" wire do ; I can find nothing. I'm guessing it is a
|
| Quote: | very
simple answer and it is just my inexperience showing through.
|
If you go back to an elementary science class, someone once told you
that if you wave a magnet around a wire, that wire will produce an
electric current. They also probably told you that if you pass a
current through a wire it will produce a magnetic field around the
wire. This was the amazing discovery of Michael Faraday and upon
which all electrical and radio theory is based.
Some alternators or generators do indeed use a permanent magnet
whirling around inside a coil of wire to produce power but the output
is directly proportional to how fast you spin it. If it makes more
output than you need you must find a way to get rid of the excess.
This is not a problem if the output is relatively small but if you
want something that can produce a lot of output for the times when
you need a lot of output, it produces way too much when you don't
need it all. Hence permanent magnet alternators, officially known as
"dynamos", tend to be small things.
But if you want one that can produce a lot of output when needed but
not much output when not needed you need a way to vary the
effectiveness. If you remember the two things that our buddy Mike
discovered, i.e. that moving magnetism generates an electric current
and moving electrons generate magnetism, you have the basic
components you need. If you want to increase the output of your
alternator at a given rotational velocity you need more magntism and
vice versa. So how can we turn the magnatism up and down as needed?
Why, we use a coil of wire with a current flowing through it. If we
increase the current, the magnetism increases and the output of our
alternator increases. If we reduce the current, the output of our
alternator decreases. This electromagnet is the rotating part of the
alternator. It is called the rotor but it is also called the field
winding from the olden days when we used generators.
A generator has the power-producing windings on the spinning part
called the armature and the magnetic field producing part, the field
windings, around the outside. An alternator has the magnetic field
windings on the spinning part (rotor) and the power-producing coils
(stator) are around the outside. You see I keep using the term
"magnetic field producing part" over again. That just got shortened
over time to the word "field".
So the way this whole thing works is to have an external sensor
determine if the alternator is producing as much power as needed. It
does this by measuring the voltage on the bus. If the voltage is too
low it allows more current to flow through the field winding. This
increases the magnetism in the center of the alternator and that then
induces more output in the stator winding. The voltage rises. If the
voltage gets higher than we want the VR reduces the current in the
field, the magnetic field is decreased, the output of the stator
windings is less, and the voltage at output is reduced. To me this
represents PFM (Pure f'n magic) and is also PFN (pretty f'n neat).
Thanks Mike!
Brian Lloyd 361 Catterline Way
brian-yak AT lloyd DOT com Folsom, CA 95630
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
Antoine de Saint-Exupry
========================
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<html><P>VERY WELL PUT !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
</P>
<P>this needs to be archived too...<BR><BR><BR>Ben Haas<BR>N801BH<B
R>www.haaspowerair.com<BR><BR>-- Brian Lloyd <brian-ya
k(at)lloyd.com> wrote:<BR>--> AeroElectric-List messag
e posted by: Brian Lloyd <brian-yak(at)lloyd.co
m><BR><BR>On May 22, 2006, at 7:19 PM,&
nbsp;Mark Chamberlain wrote:<BR>> information on&
nbsp;how to wire it, but as to the&nb
sp;questions "why?", or what<BR>> does the&n
bsp;"field" wire do ; I can find noth
ing. I'm guessing it is a <BR>>&n
bsp;very<BR>> simple answer and it is j
ust my inexperience showing through.<BR><BR>If
you go back to an elementary science
class, someone once told you <BR>that&nbs
p;if you wave a magnet around a wire,
that wire will produce an <BR>elect
ric current. They also probably told you&n
bsp;that if you pass a <BR>current t
hrough a wire it will produce a magne
tic field around the <BR>wire. This
was the amazing discovery of Michael Farad
ay and upon <BR>which all electrical 
;and radio theory is based.<BR><BR>Some alterna
tors or generators do indeed use a pe
rmanent magnet <BR>whirling around inside 
;a coil of wire to produce power but&
nbsp;the output <BR>is directly proportional&n
bsp;to how fast you spin it. If it&nb
sp;makes more <BR>output than you need&nb
sp;you must find a way to get rid&nbs
p;of the excess. <BR>This is not a&n
bsp;problem if the output is relatively sm
all but if you <BR>want something th
at can produce a lot of output for&nb
sp;the times when <BR>you need a lot
of output, it produces way too much&
nbsp;when you don't <BR>need it all. 
;Hence permanent magnet alternators, officially 
;known as <BR>"dynamos", tend to be
small things.<BR><BR>But if you want one t
hat can produce a lot of output when&
nbsp;needed but <BR>not much output when&
nbsp;not needed you need a way to var
y the <BR>effectiveness. If you remember&
nbsp;the two things that our buddy Mike&nb
sp; <BR>discovered, i.e. that moving magnetism&
nbsp;generates an electric current <BR>and&nbs
p;moving electrons generate magnetism, you have
the basic <BR>components you need.
If you want to increase the output of
your <BR>alternator at a given rota
tional velocity you need more magntism and
<BR>vice versa. So how can we
turn the magnatism up and down as nee
ded? <BR>Why, we use a coil of
wire with a current flowing through it.&nb
sp;If we <BR>increase the current, the&nb
sp;magnetism increases and the output of o
ur <BR>alternator increases. If we reduce
the current, the output of our  
;<BR>alternator decreases. This electromagnet is&nbs
p;the rotating part of the <BR>alternator
. It is called the rotor but it
is also called the field <BR>winding 
;from the olden days when we used gen
erators.<BR><BR>A generator has the power-producing&
nbsp;windings on the spinning part <BR>ca
lled the armature and the magnetic field&n
bsp;producing part, the field <BR>windings,&nb
sp;around the outside. An alternator has t
he magnetic field <BR>windings on the&nbs
p;spinning part (rotor) and the power-producing
coils <BR>(stator) are around the o
utside. You see I keep using the term
<BR>"magnetic field producing part" over
again. That just got shortened <BR>
over time to the word "field".<BR><BR>So t
he way this whole thing works is to&n
bsp;have an external sensor <BR>determine 
;if the alternator is producing as much&nb
sp;power as needed. It <BR>does this 
;by measuring the voltage on the bus. 
;If the voltage is too <BR>low it&nb
sp;allows more current to flow through the
field winding. This <BR>increases the&nb
sp;magnetism in the center of the alternat
or and that then <BR>induces more ou
tput in the stator winding. The voltage&nb
sp;rises. If the <BR>voltage gets higher&
nbsp;than we want the VR reduces the
current in the <BR>field, the magnetic&nb
sp;field is decreased, the output of the&n
bsp;stator <BR>windings is less, and the&
nbsp;voltage at output is reduced. To me&n
bsp;this <BR>represents PFM (Pure f'n mag
ic) and is also PFN (pretty f'n neat)
. <BR>Thanks Mike!<BR><BR>Brian Lloyd &n
bsp; &n
bsp; 361 
;Catterline Way<BR>brian-yak AT lloyd DOT com&n
bsp; Folsom, C
A 95630<BR>+1.916.367.2131 (voice) &nbs
p; +1.270.912.0788 (
fax)<BR><BR>I fly because it releases my m
ind from the tyranny of petty things
. . .<BR> Antoine de Saint-Exupry<BR><BR><BR><B
========================
sp; - The AeroE
p;Matronics List Features Navigator to browse<B
bsp;& Download, 7-Day Browse, Chat, FAQ,<BR
sp;--> http://www.matronics.com/Navigator?AeroElectric-List<BR>_
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the All New Matronics Email List Wiki!<BR>
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nbsp; &
========================
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sp; - List Contribution Web S
nbsp; &
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Jerry Cochran
Joined: 10 Jan 2006
Posts: 111
Location: Wilsonville, OR
|
| Posted: Wed May 24, 2006 9:41 am Post subject: Alternator Field Breaker/Switch |
|
|
Brilliant! I have passed this on to my Electron-challenged associates...
Thanks Brian.
Jerry Cochran
In a message dated 5/24/2006 12:05:43 A.M. Pacific Daylight Time,
aeroelectric-list(at)matronics.com writes:
From: Brian Lloyd <brian-yak(at)lloyd.com>
Subject: Re: Alternator Field Breaker/Switch
--> AeroElectric-List message posted by: Brian Lloyd <brian-yak(at)lloyd.com>
On May 22, 2006, at 7:19 PM, Mark Chamberlain wrote:
| Quote: | information on how to wire it, but as to the questions "why?", or what
does the "field" wire do ; I can find nothing. I'm guessing it is a
very
simple answer and it is just my inexperience showing through.
|
If you go back to an elementary science class, someone once told you
that if you wave a magnet around a wire, that wire will produce an
electric current. They also probably told you that if you pass a
current through a wire it will produce a magnetic field around the
wire. This was the amazing discovery of Michael Faraday and upon
which all electrical and radio theory is based.
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
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brian
Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA
|
| Posted: Wed May 24, 2006 12:16 pm Post subject: Alternator Field Breaker/Switch |
|
|
Jerry2DT(at)aol.com wrote:
| Quote: |
Brilliant! I have passed this on to my Electron-challenged associates...
Thanks Brian.
|
You are welcome. Sometimes we get so involved in a detailed discussion
of the trees we forget how interesting the forest is.
Brian
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_________________
Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery |
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