X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from web83907.mail.sp1.yahoo.com ([69.147.92.109] verified) by logan.com (CommuniGate Pro SMTP 5.2.13) with SMTP id 3555433 for flyrotary@lancaironline.net; Sun, 22 Mar 2009 10:46:02 -0400 Received-SPF: none receiver=logan.com; client-ip=69.147.92.109; envelope-from=delta11xd@att.net Received: (qmail 70710 invoked by uid 60001); 22 Mar 2009 14:45:25 -0000 Message-ID: <16002.68701.qm@web83907.mail.sp1.yahoo.com> X-YMail-OSG: tsvYh3cVM1lxKwZZNdmqJVWfdN13RXDreZvrQHuLfltW82DKnfJz9dr84uTt2oD8UFUsPzJ8vHQZw_vUyDEIzDTA8J_aY4Bk5LJ6tPlOeGV09FX.xsPf9BtgsIVaVrXkPxbdmeW91GQRjwutUdyogjlRdfBiXhle.5RCzzgVFtfmgiyjsVxPbu7MggE.W4SJRkwKssluCili6eh8L9nKEH_csZ2YNZlI9gRs8pdU6ePXxacCAcgYwKY- Received: from [76.243.126.69] by web83907.mail.sp1.yahoo.com via HTTP; Sun, 22 Mar 2009 07:45:24 PDT X-Mailer: YahooMailWebService/0.7.289.1 Date: Sun, 22 Mar 2009 07:45:24 -0700 (PDT) From: James Maher Reply-To: delta11xd@att.net Subject: Re: [FlyRotary] Re: Alternator (Off topic) To: Rotary motors in aircraft In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-1135658275-1237733124=:68701" --0-1135658275-1237733124=:68701 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Tom, You are right, of coarse,=A0about the alternator field being either on or o= ff. I may have implied that the field current was a linear function but I was o= nly=A0trying to simplify the explanation. =A0 However, by switching the field on and off at a=A0fairly fast rate and vary= ing the pulse width duration of the field current, a linear approximation can be achieved= with a constant voltage as the result, within the limits of the system of = course. That is in essence how the voltage regulator achieves its function. =A0 As for your "simple test" it may not give the expected results, as most mod= ern car engines, those that are controlled by computers, will have the idle= speed determined by the computer as well. So increasing the load at idle, either mechanical or electrical, will cause= the computer to sense a decrease in RPM and if it goes below a predetermined va= lue the computer will open the throttle (or idle speed valve) to increase t= he RPM to the correct idle speed. =A0 Jim --- On Sun, 3/22/09, thomas walter wrote: From: thomas walter Subject: [FlyRotary] Re: Alternator (Off topic) To: "Rotary motors in aircraft" Date: Sunday, March 22, 2009, 10:03 AM Jim, The field is either on or off.=A0=20 The regulator would create too much heat with a linear function, so solutio= n is just a 'switch' function in the regulator IC. Battery does the trick in smoothing the voltage. George -- simple test is with the engine idling, kick on the lights/fan... = note the rpm drop. That is the load of the alternator turning on. Newer vehicles will have add= itional inputs to the alternator so it knows when the AC is on, or when you= kick WOT (wide open throttle) as it will disconnect the alternator and A/C= off for a brief amount of time.=A0=A0=A0 Also a simple battery test is to = (in the car) kick on all loads at idle.... if the engine dies, battery rese= rve isn't there and time to replace 'em.=A0=A0=20 Tom 1) Re: Alternator (Off topic) =A0 =A0 by James Maher George, I'm sorry to disagree with you but you are quite mistaken in your belief ab= out the alternator function. The alternator output is mostly a function of load because of the voltage r= egulator, whose function is to keep the voltage constant with changes in load and RPM= . It performs this function by varying the field current in the alternator. If fact this is one of the many advantages of the alternator over a generat= or. The alternator's voltage output is also more or less constant regardless of= engine RPM, also due to the regulator's function. You said "The alternator charges the battery - which in turn runs the acces= sories". This is not exactly true. If the battery voltage is below that of the alter= nator output then yes the alternator will function to charge the battery, however if the= battery is fully charged then the alternator will not be charging the batt= ery but will provide the necessary power to drive any other loads connected= to the system. So reducing the electrical load on the system will indeed reduce the mechan= ical load on the engine thereby using less overall energy. Hope this clarifies your misconception. Don't feel bad, many people do not fully understand even the most simple of= electrical devices and the alternator/regulator charging system is fairly = complex.Jim --0-1135658275-1237733124=:68701 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
Tom,
You are right, of coarse, about the alternator field being either= on or off.
I may have implied that the field current was a linear function but I = was only trying to
simplify the explanation.
 
However, by switching the field on and off at a fairly fast rate = and varying the pulse
width duration of the field current, a linear approximation can be ach= ieved with a constant voltage as the result, within the limits of the syste= m of course.
That is in essence how the voltage regulator achieves its function.
 
As for your "simple test" it may not give the expected results, as mos= t modern car engines, those that are controlled by computers, will have the= idle speed determined by the computer as well.
So increasing the load at idle, either mechanical or electrical, will = cause the
computer to sense a decrease in RPM and if it goes below a predetermin= ed value the computer will open the throttle (or idle speed valve) to incre= ase the RPM to the correct idle speed.
 
Jim
--- On Sun, 3/22/09, thomas walter <round= rocktom@yahoo.com> wrote:
From: thomas walter <roundrocktom@yahoo.com>Subject: [FlyRotary] Re: Alternator (Off topic)
To: "Rotary motors in a= ircraft" <flyrotary@lancaironline.net>
Date: Sunday, March 22, 200= 9, 10:03 AM

Jim,

The field is either on or off. 

T= he regulator would create too much heat with a linear function, so solution= is just a 'switch' function in the regulator IC.

Battery does the t= rick in smoothing the voltage.

George -- simple test is with the eng= ine idling, kick on the lights/fan... note the rpm drop.
That is the loa= d of the alternator turning on. Newer vehicles will have additional inputs = to the alternator so it knows when the AC is on, or when you kick WOT (wide= open throttle) as it will disconnect the alternator and A/C off for a brie= f amount of time.    Also a simple battery test is to (in th= e car) kick on all loads at idle.... if the engine dies, battery reserve is= n't there and time to replace 'em.  

Tom



<= BR>


1) Re: Alternator (Off topic)
  &nbs= p; by James Maher <delta11xd@att.net>

George,
I'm sorry to disagree with you but you are quite mistaken in your beli= ef about the
alternator function.
The alternator output is mostly a function of load because of the volt= age regulator,
whose function is to keep the voltage constant with changes in load an= d RPM.
It performs this function by varying the field current in the alternat= or.
If fact this is one of the many advantages of the alternator over a ge= nerator.
The alternator's voltage output is also more or less constant regardle= ss of engine RPM, also due to the regulator's function.
You said "The alternator charges the battery - which in turn runs the = accessories".
This is not exactly true. If the battery voltage is below that of the = alternator output
then yes the alternator will function to charge the battery, however i= f the battery is fully charged then the alternator will not be charging the= battery but will provide the necessary power to drive any other loads conn= ected to the system.
So reducing the electrical load on the system will indeed reduce the m= echanical load on
the engine thereby using less overall energy.
Hope this clarifies your misconception.
Don't feel bad, many people do not fully understand even the most simp= le of electrical devices and the alternator/regulator charging system is fa= irly complex.
Jim

=
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