X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 22 Oct 2012 10:13:51 -0400 Message-ID: X-Original-Return-Path: Received: from web120105.mail.ne1.yahoo.com ([98.138.85.152] verified) by logan.com (CommuniGate Pro SMTP 6.0c2) with ESMTPS id 5836143 for lml@lancaironline.net; Mon, 22 Oct 2012 07:18:53 -0400 Received-SPF: none receiver=logan.com; client-ip=98.138.85.152; envelope-from=casey.gary@yahoo.com Received: (qmail 1703 invoked by uid 60001); 22 Oct 2012 11:18:17 -0000 DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=X-YMail-OSG:Received:X-Rocket-MIMEInfo:X-Mailer:References:Message-ID:Date:From:Reply-To:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=SqrZ3AvoYeyTbualjgzyo8bIuqe/U9nLhEkumJxgUmh7Yrapd1Y0stvYowV68HvZhD3F97Tp0l/kIyPi9llr0r745e/iPOLQQBV5dyoA35WDq0rj9WGKGHbTfgtVQMFyIdptYjnp7qQlOEhg6f9DtJI7+Yb5hnRg0tdUT+YEydQ=; X-YMail-OSG: Tl6B534VM1mHNs0c2v.x6QRVvnXv04fh6jfG6ts_GvJE8MK kTL.vcAGyaRN1EaDvJ5pR_gE.Ov3vVf7D_UdtfndcKvc2MCgr.fJSGlAVRoX Zmr1gbvAXrxrXcOLucAiDVJ_w.3TOc1KRbtqF0e1FLRSq1qSJtDJWaeg.92L mWXPWch9uLaqBC7Ka5zj39Ni.bM_QC.NA4B1A4.zAxSfZ8xRVEd.5AbXOcdZ 58nz35GnRf7OiCforFw8l3FweMoj0bsOZECsj8OinpVKi1.moatCOIXUNzFY hOzClM2UwqIIdI7gueVuX0arFIoJ_i4gmYdvYAyJFGpRP48nPYT5uHeIsiZQ .Ad8hexGGS6d7MBTJdVknp2izH3xtzMAk01nSJGfPOjqjUxp3XwFEUOxlvi8 A6rUR_6gayGvIX8cf0yUf1A91UZXNU7WDWI5WJJxfRmh.3qELW8Xk6ByUApW TK1IY6BwkNB4Nk8VRlQ4ElsPpgvnmeBy3rxYFLCyWrKWDRjveuHsc1mRaDY5 hd1MwhA6RZyKb Received: from [71.218.254.50] by web120105.mail.ne1.yahoo.com via HTTP; Mon, 22 Oct 2012 04:18:17 PDT X-Rocket-MIMEInfo: 001.001,UGF1bCwKSSB3YXMgdHJ5aW5nIHRvIHNheSB3aGF0IEJyZW50IHNhaWQsIGJ1dCBoZSBzYWlkIGl0IG11Y2ggbW9yZSBlbGVnYW50bHkuIMKgSXQgcmVhbGx5IGFsbCBkZXBlbmRzIG9uIHRoZSBtZXRob2RvbG9neSB1c2VkIGluIHRoZSByYXRpbmcgb2YgdGhlIGRpb2Rlcy4gwqBJcyB0aGUgZGlvZGUgcGFja2FnZSByYXRlZCBhdCB0aGUgY3VycmVudCBvZiB0aGUgaW5kaXZpZHVhbCBkaW9kZXMgaW4gdGhlIHBhY2thZ2U_IMKgT3IgaXMgaXQgcmF0ZWQgYXQgdGhlIGN1cnJlbnQgcHJvZHVjZWQgYnkgdGhlIGEBMAEBAQE- X-Mailer: YahooMailWebService/0.8.123.460 References: X-Original-Message-ID: <1350904697.86791.YahooMailNeo@web120105.mail.ne1.yahoo.com> X-Original-Date: Mon, 22 Oct 2012 04:18:17 -0700 (PDT) From: Gary Casey Reply-To: Gary Casey Subject: Re: TCM 60A alternator--diodes X-Original-To: Lancair Mailing List In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-1460980517-1602550987-1350904697=:86791" ---1460980517-1602550987-1350904697=:86791 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Paul,=0AI was trying to say what Brent said, but he said it much more elega= ntly. =A0It really all depends on the methodology used in the rating of the= diodes. =A0Is the diode package rated at the current of the individual dio= des in the package? =A0Or is it rated at the current produced by the altern= ator into which it is intended to be mounted? =A0And the the rating is also= "derated" as a function of temperature, and at the core each diode is rate= d depending on the junction temperature within the diode. =A0What I'm sayin= g is that it gets complicated. =A0I assume a front-mounted alternator runs = very cool, so that's a good thing. =A0As I recall, most alternators put out= a frequency that is 7 times their rpm (why I remember that I don't know :-= ) and the alternator runs a a speed that I assume is at least twice cranksh= aft speed. =A0But, the electrical noise you hear is not the ripple from the= windings, but the voltage transient caused by the turn-on delay of the dio= des. =A0Diodes don't turn on instantly, so the voltage in a winding will rise a= bove battery voltage and then suddenly drop as the diode turns on, and that= happens three times per cycle. =A0That will give you the frequency of the = "whine" you sometimes hear in the headset, which using those numbers comes = out to at least 1,680 Hz at 2400 rpm. =A0If there is a capacitor in the alt= ernator, that's what it's for, not to reduce the ripple. =A0Look carefully = at the alternator voltage (also at battery voltage) and you'll see small, v= ery short spikes in the voltage caused by the diodes. =A0A "picket fence" l= ook.=0AAnd I wasn't trying to be judgmental or anything - I was trying to p= oint out that our conservatism in any design is a function of intended usag= e. =A0If it is only for day VFR in sparsely-used airspace the whole electri= cal system is a convenience and one might not be too concerned about the re= liability of the alternator. =A0So the choices one makes are a function of = intended usage.=0AGary=0A=0AGary: I have to disagree and I don't think this= alternator works the way you describe. =A0This is multi-phase high frequen= cy alternator that has multiple poles and three windings. =A0The result is = that all the circuits are producing AC high frequency 3-phase rectified out= put and the output is indeed additive from the 6 diode outputs in the sinus= oidal sense. Plus, we're not running at 60Hz but a far higher frequency wit= h six pulses per pole, multiple poles (12 or 14) and somewhere around 7000r= pm at cruise.=0A=0AThe result in a very high effective DC output voltage wi= th limited ripple. That's why it gets dumped right into the aircraft buss w= ith only the small capacitor located inside the alternator =A0All the diode= s are working all the time and they don't "take turns" in sequence. =A0Each= diode is rated at 50A continuous and the three phases are actually additiv= e, overlapping sine waves. =A0 Take away a phase by removing a winding and = you will generate less amperage. =A0The output from this configuration is a= bout 1.73x the peak phase voltage and I extrapolate that to be directly pro= portional for current also. =A0See the diagram attached for reference. Ther= efore, I calculate each phase only needs 19.5A (100A over 3 phases divided = by 1.71) to produce 100A output. =A0 That 19.5A maximum per phase is far le= ss than the 50A rating we're discussing and suggests a large margin exists.= Realistically, 100A units are run somewhere less than 100% =A0max continuo= us load calculations which suggests even more margin is built in.=0A=0AHaving said= that, the unit described is typically use for high output amperage truck a= lternators in the 90A range and you can do your own research to verify the = applications. You might also want to check the diode sizing in the TCM 60A = alternator to see how that compares with the 50s I replaced those with.=0A= =0AYour last comment seemed to suggest some form of risky behaviour was bei= ng contemplated by this thread. Some nonsense about night IFR or whatever. = =A0I think it was unnecessary and a pointless addition to what was intended= to be an informative discussion.=0A=0APaul=0ALegacy, Calgary ---1460980517-1602550987-1350904697=:86791 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
Paul,
I was trying to say = what Brent said, but he said it much more elegantly.  It really all de= pends on the methodology used in the rating of the diodes.  Is the dio= de package rated at the current of the individual diodes in the package? &n= bsp;Or is it rated at the current produced by the alternator into which it = is intended to be mounted?  And the the rating is also "derated" as a function of temperature, and at the core each diode is rated depending on = the junction temperature within the diode.  What I'm saying is that it= gets complicated.  I assume a front-mounted alternator runs very cool= , so that's a good thing.  As I recall, most alternators put out a fre= quency that is 7 times their rpm (why I remember that I don't know :-) and = the alternator runs a a speed that I assume is at least twice crankshaft sp= eed.  But, the electrical noise you hear is not the ripple from the wi= ndings, but the voltage transient caused by the turn-on delay of the diodes= .  Diodes don't turn on instantly, so the voltage in a winding will ri= se above battery voltage and then suddenly drop as the diode turns on, and = that happens three times per cycle.  That will give you = the frequency of the "whine" you sometimes hear in the headset, which using= those numbers comes out to at least 1,680 Hz at 2400 rpm.  If there is a capacitor in the alternator, that's what it's for, not to reduc= e the ripple.  Look carefully at the alternator voltage (also at batte= ry voltage) and you'll see small, very short spikes in the voltage caused b= y the diodes.  A "picket fence" look.
And I wasn't trying to be judgmental or an= ything - I was trying to point out that our conservatism in any design is a= function of intended usage.  If it is only for day VFR in sparsely-us= ed airspace the whole electrical system is a convenience and one might not = be too concerned about the reliability of the alternator.  So the choi= ces one makes are a function of intended usage.
Gary<= /div>

G= ary: I have to disagree and I don't think this alternator works the way you= describe.  This is multi-phase high frequency alternator that has multiple pole= s and three windings.  The result is that all the circuits are produci= ng AC high frequency 3-phase rectified output and the output is indeed addi= tive from the 6 diode outputs in the sinusoidal sense. Plus, we're not runn= ing at 60Hz but a far higher frequency with six pulses per pole, multiple p= oles (12 or 14) and somewhere around 7000rpm at cruise.

= The result in a very high effective DC output voltage with limited ripple. = That's why it gets dumped right into the aircraft buss with only the small = capacitor located inside the alternator  All the diodes are working al= l the time and they don't "take turns" in sequence.  Each diode is rat= ed at 50A continuous and the three phases are actually additive, overlappin= g sine waves.   Take away a phase by removing a winding and you will g= enerate less amperage.  The output from this configuration is about 1.73x the peak phase voltage and I extrapolate that to be directly p= roportional for current also.  See the diagram attached for reference.= Therefore, I calculate each phase only needs 19.5A (100A over 3 phases div= ided by 1.71) to produce 100A output.   That 19.5A maximum per phase i= s far less than the 50A rating we're discussing and suggests a large margin= exists. Realistically, 100A units are run somewhere less than 100%  m= ax continuous load calculations which suggests even more margin is built in= .

Having said that, the unit described is typically use = for high output amperage truck alternators in the 90A range and you can do = your own research to verify the applications. You might also want to check = the diode sizing in the TCM 60A alternator to see how that compares with th= e 50s I replaced those with.

Your last comment see= med to suggest some form of risky behaviour was being contemplated by this thread. Some nonsense about night IFR or whatever.  I think i= t was unnecessary and a pointless addition to what was intended to be an in= formative discussion.

Paul
Legacy, Calga= ry


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