X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao102.cox.net ([68.230.241.44] verified) by logan.com (CommuniGate Pro SMTP 5.2.13) with ESMTP id 3555460 for flyrotary@lancaironline.net; Sun, 22 Mar 2009 11:38:03 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.44; envelope-from=rv-4mike@cox.net Received: from fed1rmimpo03.cox.net ([70.169.32.75]) by fed1rmmtao102.cox.net (InterMail vM.7.08.02.01 201-2186-121-102-20070209) with ESMTP id <20090322153726.SUOB13097.fed1rmmtao102.cox.net@fed1rmimpo03.cox.net> for ; Sun, 22 Mar 2009 11:37:26 -0400 Received: from wills ([68.105.85.56]) by fed1rmimpo03.cox.net with bizsmtp id WFdN1b0071CvZmk04FdRAU; Sun, 22 Mar 2009 11:37:25 -0400 X-Authority-Analysis: v=1.0 c=1 a=nvsZiLXK4VwA:10 a=zZEb6FtgOScA:10 a=CjxXgO3LAAAA:8 a=Ia-xEzejAAAA:8 a=HZJGGiqLAAAA:8 a=-xwbl73nuY4vLRt_wdUA:9 a=hGqOVk-y-aX3Rl4Au_YA:7 a=3IelhM5ko_HhAt137Rg4g8F0MxAA:4 a=1DF-ZbDQmksA:10 a=rC2wZJ5BpNYA:10 a=EzXvWhQp4_cA:10 a=HeoGohOdMD0A:10 a=bFs70vSn9vdNCSWV_B8A:9 a=-68l56j2mH27jNr895EA:7 a=OjZ8SGwjYq0LsDjDZ8aMGHbjegEA:4 a=AfD3MYMu9mQA:10 X-CM-Score: 0.00 Message-ID: <003801c9ab04$162a7570$38556944@wills> From: "Mike Wills" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Alternator (Off topic) Date: Sun, 22 Mar 2009 08:37:19 -0700 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0035_01C9AAC9.6969CE60" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3138 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3350 This is a multi-part message in MIME format. ------=_NextPart_000_0035_01C9AAC9.6969CE60 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Slightly off topic, but does anyone have a suggestion for an off the = shelf filter to kill/reduce alternator electrical noise? I have an = alternator off of a Geo Metro/Chevy Sprint with internal regulator. I = have a switch on the panel to energize the field. After the engine is = running and I switch on the alternator I get a noticeable hum in the = intercom. This is one of those nagging little issues I havent gotten = around to fixing yet since first flight. Also in a previous thread someone (maybe Al G.?) mentioned an = over-voltage protection device for the alternator output that would be = compatible with the internally regulated alternator. I'd like to add = something like that as well - suggested sources? Thanks, Mike Wills RV-4 N144MW ----- Original Message -----=20 From: James Maher=20 To: Rotary motors in aircraft=20 Sent: Sunday, March 22, 2009 7:45 AM Subject: [FlyRotary] Re: Alternator (Off topic) 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 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. As for your "simple test" it may not give the expected results, = as most 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 = predetermined value the computer will open the throttle (or idle speed = valve) to increase the RPM to the correct idle speed. 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. =20 The regulator would create too much heat with a linear = function, so solution 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 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 brief amount of time. = Also a simple battery test is to (in the car) kick on all loads at = idle.... if the engine dies, battery reserve isn't there and time to = replace 'em. =20 Tom 1) Re: Alternator (Off topic) by James Maher George, I'm sorry to disagree with you but you are quite = mistaken in your belief about the alternator function. The alternator output is mostly a function of load = because of the voltage regulator, 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 generator. 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 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 if 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 connected to the system. So reducing the electrical load on the system will = indeed reduce the mechanical 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 =20 =20 ------=_NextPart_000_0035_01C9AAC9.6969CE60 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Slightly off topic, but does anyone = have a=20 suggestion for an off the shelf filter to kill/reduce alternator = electrical=20 noise? I have an alternator off of a Geo Metro/Chevy Sprint with = internal=20 regulator. I have a switch on the panel to energize the field. After the = engine=20 is running and I switch on the alternator I get a noticeable hum in the=20 intercom. This is one of those nagging little issues I havent gotten = around to=20 fixing yet since first flight.
 
 Also in a previous thread someone = (maybe Al=20 G.?) mentioned an over-voltage protection device for the alternator = output that=20 would be compatible with the internally regulated alternator. I'd = like to=20 add something like that as well - suggested sources?
 
Thanks,
 
Mike Wills
RV-4 N144MW
----- Original Message -----
From:=20 James = Maher=20
Sent: Sunday, March 22, 2009 = 7:45=20 AM
Subject: [FlyRotary] Re: = Alternator (Off=20 topic)

Tom,
You are right, of coarse, about the alternator field = being=20 either on or off.
I may have implied that the field current was a linear = function but=20 I was only trying to
simplify the explanation.
 
However, by switching the field on and off at a fairly = fast=20 rate and varying the pulse
width duration of the field current, a linear approximation = can be=20 achieved with a constant voltage as the result, within the = limits of the=20 system of course.
That is in essence how the voltage regulator achieves its=20 function.
 
As for your "simple test" it may not give the expected = results, as=20 most modern car engines, those that are controlled by computers, = will=20 have the idle speed determined by the computer as well.
So increasing the load at idle, either mechanical or = electrical,=20 will cause the
computer to sense a decrease in RPM and if it goes below a=20 predetermined value the computer will open the throttle (or idle = speed=20 valve) to increase the RPM to the correct idle speed.
 
Jim
--- On Sun, 3/22/09, thomas walter=20 <roundrocktom@yahoo.com> wrote:
From:=20 thomas walter <roundrocktom@yahoo.com>
Subject: = [FlyRotary]=20 Re: Alternator (Off topic)
To: "Rotary motors in aircraft"=20 <flyrotary@lancaironline.net>
Date: Sunday, March 22, = 2009,=20 10:03 AM

Jim,

The field is either on or = off. =20

The regulator would create too much heat with a = linear=20 function, so solution is just a 'switch' function in the = regulator IC.

Battery does the trick in smoothing = the=20 voltage.

George -- simple test is with the engine = idling,=20 kick on the lights/fan... note the rpm drop.
That is = the load=20 of the alternator turning on. Newer vehicles will have=20 additional inputs to the alternator so it knows when the = AC is=20 on, or when you kick WOT (wide open throttle) as it will = disconnect the alternator and A/C off for a brief amount = of=20 time.    Also a simple battery test is to = (in the=20 car) kick on all loads at idle.... if the engine dies, = battery=20 reserve isn't there and time to replace 'em.   =

Tom






1) Re: Alternator (Off=20 topic)
    by James Maher <delta11xd@att.net>

George,
I'm sorry to disagree with you but you are quite = mistaken=20 in your belief about the
alternator function.
The alternator output is mostly a function of = load=20 because of the voltage regulator,
whose function is to keep the voltage constant = with=20 changes in load and RPM.
It performs this function by varying the field = current in=20 the alternator.
If fact this is one of the many advantages of the = alternator over a generator.
The alternator's voltage output is also more or = less=20 constant regardless of engine RPM, also due to the = regulator's=20 function.
You said "The alternator charges the battery - = which in=20 turn runs the accessories".
This is not exactly true. If the battery voltage = is below=20 that of the alternator output
then yes the alternator will function to charge = the=20 battery, however if the battery is fully charged then = the=20 alternator will not be charging the battery but will = provide=20 the necessary power to drive any other loads connected = to the=20 system.
So reducing the electrical load on the system = will indeed=20 reduce the mechanical 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=20 the most simple of electrical devices and the=20 alternator/regulator charging system is fairly=20 = complex.
Jim

= ------=_NextPart_000_0035_01C9AAC9.6969CE60--