Return-Path: Received: from mtain-de01.r1000.mx.aol.com (mtain-de01.r1000.mx.aol.com [172.29.64.201]) by air-md10.mail.aol.com (v129.4) with ESMTP id MAILINMD103-8b9a4d3b22c7394; Sat, 22 Jan 2011 13:32:39 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-de01.r1000.mx.aol.com (Internet Inbound) with ESMTP id 4D6633800008D; Sat, 22 Jan 2011 13:32:37 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PgiFY-0005pK-9m for rs_out_1@blacksheep.org; Sat, 22 Jan 2011 18:31:48 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PgiFX-0005pB-O4 for rsgb_lf_group@blacksheep.org; Sat, 22 Jan 2011 18:31:47 +0000 Received: from cavuit01.kulnet.kuleuven.be ([134.58.240.43]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1PgiFV-0008I7-Bb for rsgb_lf_group@blacksheep.org; Sat, 22 Jan 2011 18:31:47 +0000 Received: from smtps01.kuleuven.be (smtpshost01.kulnet.kuleuven.be [134.58.240.74]) by cavuit01.kulnet.kuleuven.be (Postfix) with ESMTP id B11287B804D for ; Sat, 22 Jan 2011 19:31:37 +0100 (CET) Received: from ICTS-S-HUB-N2.luna.kuleuven.be (icts-s-hub-n2.luna.kuleuven.be [10.112.9.12]) by smtps01.kuleuven.be (Postfix) with ESMTP id A771E31E702 for ; Sat, 22 Jan 2011 19:31:37 +0100 (CET) Received: from ICTS-S-EXC2-CA.luna.kuleuven.be ([10.112.11.13]) by ICTS-S-HUB-N2.luna.kuleuven.be ([10.112.9.12]) with mapi; Sat, 22 Jan 2011 19:31:37 +0100 X-Kuleuven: This mail passed the K.U.Leuven mailcluster From: Rik Strobbe To: "rsgb_lf_group@blacksheep.org" Date: Sat, 22 Jan 2011 19:31:36 +0100 Thread-Topic: Thick Litz wire needed, and more on class E PA development Thread-Index: Acu6WDIcq0mI4nW9TPSxcQnP143bzwABnqqq Message-ID: References: In-Reply-To: Accept-Language: nl-NL, nl-BE Content-Language: nl-BE X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: nl-NL, nl-BE MIME-Version: 1.0 X-KULeuven-Information: Katholieke Universiteit Leuven X-KULeuven-Scanned: Found to be clean X-KULeuven-Envelope-From: rik.strobbe@fys.kuleuven.be X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: LF: RE: Thick Litz wire needed, and more on class E PA development Content-Type: multipart/alternative; boundary="_000_BF4A524700075746A6467658DFC7102C88715AEAA6ICTSSEXC2CAlu_" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=HTML_MESSAGE, TO_ADDRESS_EQ_REAL autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false x-aol-global-disposition: G x-aol-sid: 3039ac1d40c94d3b22c53f49 X-AOL-IP: 195.171.43.25 X-Mailer: Unknown (No Version) --_000_BF4A524700075746A6467658DFC7102C88715AEAA6ICTSSEXC2CAlu_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hello Andy, with 9.3UH the class E amp must have a rather high Q (12 ?). Maybe a lower= Q (and more or less proportional lower L) might help ? 73, Rik ON7YD - OR7T ________________________________ Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.or= g] namens Andy Talbot [andy.g4jnt@gmail.com] Verzonden: zaterdag 22 januari 2011 18:14 Aan: rsgb_lf_group@blacksheep.org Onderwerp: LF: Thick Litz wire needed, and more on class E PA development Is there still any of the really thick Litz wire from the old Decca statio= ns around? I'm after about 3 to 3.5 metres of whatever is available that= is thicker than 3mm, and preferably nearer 3.5mm diameter. Enough to= make a 9.3uH coil The Tank coil in the latest version of the class E PA under test is now th= e power-determining item. At 450 Watts output the heatsink with fan is= COLD - but the coil annoyingly smells of hot varnish. It is wound with the cotton covered Litz, about 2.5mm overall diameter whi= ch itself is a big improvement over the plastic covered stuff I was using= for the breadboard. But, I have the surreal situation that as teh coil= gets hot, teh wire expands, inductance falls and due to the nature of the= combined Tank + L-Match circuitry causes a resulting increase in powser= output - leadign to higher dissipation and you can guess what will eventu= ally happen if left unchecked. One soluition will be to duct air from the fan through the coil, but I'd= feel happier if loses were lower to start with. At reduced Vdd it reaches stability running at 400 Watts without getting= too hot and increasing itself spontaneously. Efficiency, by the way, variously measures at 86 - 94%. So I'll say aroun= d 88%. Hard to believe, but I have been over everything and double chec= ks, and can't get teh value below 84% however much I try to push errors in= the worst direction. The FETs are now a pair of IRFP360, and the driver chip had to be replace= d - the poor ICL7667 just went bang and split itself open driving them. = The copper of the PCB tracks running under it became discoloured so it mu= st have bene running very hot before dying Now using a pair of SMT TC4420= devices - one per FET - with additional copper heat dissipating fins on= the PCB. They've survived so far. Its been delivering 320 Watts for an hour now off a 37V rail, so at that= power level is certainly reliable; brief forays up to a 55V rail gave sli= ghtly over 700 Watts - and I could see current rising as I watched due to= the coil expanding, so didn't hold it there for long, but does mean the= PA as it stands could be used with AM/envelope modulation. The shack is getting quite warm now ! A second chapter to the write-up will appear in due course Andy www.g4jnt.com --_000_BF4A524700075746A6467658DFC7102C88715AEAA6ICTSSEXC2CAlu_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hello Andy,
 
with 9.3UH the class E amp = ;must have a rather high Q (12 ?). Maybe a lower Q (and more or less= proportional lower L) might help ?
 
73, Rik  ON7YD - OR7T
 
Van: owner-rsgb_= lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] namens Andy= Talbot [andy.g4jnt@gmail.com]
Verzonden: zaterdag 22 januari 2011 18:14
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: LF: Thick Litz wire needed, and more on class E PA devel= opment

Is there still any of the really thick Litz wire from the old Decca= stations around?   I'm after about 3 to 3.5 metres of what= ever is available that is thicker than 3mm, and preferably nearer 3.5mm di= ameter.    Enough to make a 9.3uH coil
 
The Tank coil in the latest version of the class E PA under test= is now the power-determining item.   At 450 Watts output the he= atsink with fan is COLD - but the coil annoyingly smells of hot varnish.
It is wound with the cotton covered Litz, about 2.5mm overall diamete= r which itself is a big improvement over the plastic covered stuff I was= using for the breadboard.  But, I have the surreal situation that as= teh coil gets hot, teh wire expands, inductance falls and due to the nature of the combined Tank + L-Match circuitry= causes a resulting increase in powser output - leadign to higher dissipation= and you can guess what will eventually happen if left unchecked.
 
One soluition will be to duct air from the fan through the coil, but= I'd feel happier if loses were lower to start with.
 
At reduced Vdd it reaches stability running at 400 Watts without gett= ing too hot and increasing itself spontaneously.
 
Efficiency, by the way, variously measures at 86 - 94%.  So I'll= say around 88%.    Hard to believe, but I have been= over everything and double checks, and can't get teh value below 84% howe= ver much I try to push errors in the worst direction.
 
The FETs are now a pair of IRFP360, and the  driver chip ha= d to be replaced - the poor ICL7667 just went bang and split itself open= driving them.  The copper of the PCB tracks running under = it became discoloured so it must have bene running very hot before dying  Now using a pair of SMT TC4420 devices - one per FET -  = with additional copper heat dissipating fins on the PCB.   = They've survived so far.
 
Its been delivering  320 Watts for an hour now off a 37V rail,= so at that power level is certainly reliable; brief forays up to a= 55V rail gave slightly over 700 Watts - and I could see current rising as= I watched due to the coil expanding, so didn't hold it there for long, but does mean the PA as it stands could be used with= AM/envelope modulation.
 
The shack is getting quite warm now !
A second chapter to the write-up will appear in due course
 
Andy
 
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