Return-Path: Received: from [24.25.9.102] (HELO ms-smtp-03-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.2b5) with ESMTP id 143003 for flyrotary@lancaironline.net; Mon, 07 Jun 2004 13:09:17 -0400 Received: from EDWARD (clt25-78-058.carolina.rr.com [24.25.78.58]) by ms-smtp-03-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id i57H8hLr024927 for ; Mon, 7 Jun 2004 13:08:44 -0400 (EDT) Message-ID: <000f01c44cb2$19d585d0$2402a8c0@EDWARD> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Average vs Instanteous Power was Re: LS1 Coils - amp draw? Date: Mon, 7 Jun 2004 13:08:48 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_000C_01C44C90.926BB3B0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1409 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1409 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_000C_01C44C90.926BB3B0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message=20 =20 Tracy; Well; the worry is this. Safe wiring practice requires being able = to protect the wire, especially if it is in a bundle or close proximity = with other wires, against any failure which would overload the wire. = Running the numbers says that the maximum safe current for a 16 awg wire = is 15 amps. If I interpret you correctly; it is possible for my coil = power lead to have to carry 27 amps (for 3 coils) for a short time, = which would trip a breaker, or blow a fuse. Under these conditions one = can not properly protect the wire against a potential short - unless a = much larger wire is used. My wires run in a wiring duct, which isn't = exactly a bundle, but the analysis says for 27 amps in a bundle you need = about a #10 wire. Further; I went to great lengths to maintain the redundancy that you = also strived for in the ECU with the dual controllers and the isolation = switches. I have the engine critical bus connected to the dual battery = system, and isolated by 40 amp diodes. I think you're suggesting that = it's possible for the coils to momentarily draw 54 amps (6 x 9), plus = pump and injectors; maybe up to nearly 70 amps. Ain't gonna work. So what am I misunderstanding here, or how do we get around this? = Under what temporary condition can this high current exist? Is there an = operational sequence to avoid this possible condition? Thanks, Al Al, not Tracy, but I think what Tracy is saying that in the = milliseconds or so it takes the EC2 to calculate the proper coil dwell = time it is possible for a coil(s) to draw up to 9 amps (or perhaps even = 27 amps in your case). The instantaneous power in that case would be = 27*12 =3D 324 watts IF that current drain remained for as much as 1 = second (actually probably less because when cranking you probably would = not have more than 10 volts). However, I believe the duration of that = surge is much shorter duration. IF I am correct then I suspect your 16 = gauge wire is more than adequate because of the very short time interval = in which this happens (I'm guessing that situation does not last for = even 100 milliseconds, Tracy??).=20 If that is the case then the power (which is what we are really = concerned about) per second would be 1/10*27*12 =3D 32.4 watts average = power consumed during that time. The very conservative Power = transmission (bundled) for 16 gauge is 3.7 amps x 12 volts =3D 44.4 = watts. Therefore, IF the surge is l00 milliseconds duration or less then = it would appear you wiring is more than adquate. Now if the surge = condition can actually last for as long a second then its a different = story. Ed=20 =20 ------=_NextPart_000_000C_01C44C90.926BB3B0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message
 
 

Tracy;

 

Well; = the worry=20 is this.  Safe wiring practice requires being able to protect = the wire,=20 especially if it is in a bundle or close proximity with other wires, = against=20 any failure which would overload the wire.  Running the numbers = says=20 that the maximum safe current for a 16 awg wire is 15 amps.  If = I=20 interpret you correctly; it is possible for my coil power lead to = have to=20 carry 27 amps (for 3 coils) for a short time, which would trip a = breaker, or=20 blow a fuse.  Under these conditions one can not properly = protect the=20 wire against a potential short =96 unless a much larger wire is = used.  My=20 wires run in a wiring duct, which isn=92t exactly a bundle, but the = analysis=20 says for 27 amps in a bundle you need about a #10 = wire.

 

Further; I went=20 to great lengths to maintain the redundancy that you also strived = for in the=20 ECU with the dual controllers and the isolation switches.  I = have the=20 engine critical bus connected to the dual battery system, and = isolated by 40=20 amp diodes.  I think you=92re suggesting that it=92s possible = for the coils=20 to momentarily draw 54 amps (6 x 9), plus pump and injectors; maybe = up to=20 nearly 70 amps.  = Ain=92t=20 gonna work.

 

So what = am I=20 misunderstanding here, or how do we get around this?  Under = what=20 temporary condition can this high current exist?  Is there an=20 operational sequence to avoid this possible = condition?

 

Thanks,

 

Al

 

 

Al, not = Tracy,=20 but I think what Tracy is saying that in the milliseconds = or so it=20 takes the EC2 to calculate the proper coil dwell time it is possible = for a=20 coil(s) to draw up to 9 amps (or perhaps even 27 amps in your=20 case).   The instantaneous = power in=20 that case  would be 27*12 =3D 324 watts IF = that current=20 drain remained for as much as 1 second (actually probably less = because when=20 cranking you probably would not have more than 10 volts).  = However, I=20 believe the duration of that surge is much shorter = duration. =20 IF I am correct then I suspect your 16 gauge wire is more than = adequate=20 because of the very short time interval in which this happens (I'm = guessing=20 that situation does not last for even 100 milliseconds,=20 Tracy??). 

 

 If that is=20 the case then the power (which is what we are really concerned=20 about) per second would be 1/10*27*12 =3D 32.4=20 watts average power consumed during that time.  The very = conservative=20 Power transmission (bundled) for 16 gauge is 3.7 amps x 12 volts =3D = 44.4=20 watts. Therefore, IF the surge is l00 milliseconds duration or less = then it=20 would appear you wiring is more than adquate. Now if the surge=20 condition can actually last for as long a second then its a = different=20 story.

 

Ed=20

 

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