Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-2.1 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, RCVD_IN_DNSWL_MED,SPF_PASS,STOX_REPLY_TYPE,T_DKIM_INVALID autolearn=ham autolearn_force=no version=3.4.0 X-Spam-DCC: : mailn 1480; Body=2 Fuz1=2 Fuz2=2 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by lipkowski.org (8.14.4/8.14.4/Debian-8+deb8u1) with ESMTP id v52Cgrkh013385 for ; Fri, 2 Jun 2017 14:42:54 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1dGlpT-0001ST-T0 for rs_out_1@blacksheep.org; Fri, 02 Jun 2017 13:37:23 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1dGlpR-0001SK-J7 for rsgb_lf_group@blacksheep.org; Fri, 02 Jun 2017 13:37:21 +0100 Received: from rgout0103.bt.lon5.cpcloud.co.uk ([65.20.0.123] helo=rgout01.bt.lon5.cpcloud.co.uk) by relay1.thorcom.net with esmtp (Exim 4.89) (envelope-from ) id 1dGlpM-0000W1-PT for rsgb_lf_group@blacksheep.org; Fri, 02 Jun 2017 13:37:19 +0100 X-OWM-Source-IP: 109.146.90.196 (GB) X-OWM-Env-Sender: alan.melia@btinternet.com X-Junkmail-Premium-Raw: score=8/50,refid=2.7.2:2017.5.13.91815:17:8.707,ip=,rules=NO_URI_FOUND, NO_CTA_URI_FOUND, NO_MESSAGE_ID, NO_URI_HTTPS, TO_MALFORMED Received: from gnat (109.146.90.196) by rgout01.bt.lon5.cpcloud.co.uk (9.0.019.13-1) (authenticated as alan.melia@btinternet.com) id 58F62BE304DB9080 for rsgb_lf_group@blacksheep.org; Fri, 2 Jun 2017 13:37:15 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=btinternet.com; s=btcpcloud; t=1496407036; bh=GZ9ErnRvDqsot0ibEvx5rTr7BUoKWgcOE/ODZ7wD5tA=; h=Message-ID:From:To:References:Subject:Date:MIME-Version:X-Mailer; b=hykBmxh9qNwhGG5HxA2uabbzut5OgsTWVccUY2CJ6SIZr0K2KFdnmmjWLRJitDsZRvvwnH1k+BtC4aFFNmEtbgi5M9oEzN9+0Yx42drnW8mZKsQ8k8z0OCy/kBZAPzTxLrPXBGJZjpl53mDRvZSshFrMz9nOOGnx9pRH3hwhCCs= Message-ID: From: "Alan Melia" To: References: <15c68b2d2ed.marcocadeddu@tin.it> Date: Fri, 2 Jun 2017 13:36:37 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5931 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157 X-Scan-Signature: 6bd672f829af6a22357e8edf5ae2addd Subject: LF: Re: I: Fw: For today the FETs survived... Content-Type: text/plain; format=flowed; charset="utf-8"; reply-type=original Content-Transfer-Encoding: 8bit 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-Scanned-By: MIMEDefang 2.75 Status: O X-Status: X-Keywords: X-UID: 11854 Hi Marco I dont know where you are putting the caps but I am assuming they are passing a high RF corrent. I found that the old style (valve) high voltage caps in my Class E test rig changed capacitance permanently during and after a run (capacitance reduced). I assumed that the current was fusing the foil connection to the lead-out wires. When using "pulse rated" capacitors as used in SMPSUs I had no further capacitance change problems. The ones I have are RIFA PHE 428 2000v from RS Components. I think Farnell do a WIMA equivalent. Best Wishes Alan G3NYK ----- Original Message ----- From: To: Sent: Friday, June 02, 2017 1:06 PM Subject: R: Re: Re: Re: LF: Re: I: Fw: For today the FETs survived... now my thoughts are even more confused.... Hi Andy, me again.... after a long night of meditation, I remembered I had a bounch of old style mica capacitators 1000pF 1000V.. I put 9 of them in parallel to get the closer value to the 8800pF I had before. Of course the resonance moved a bit and now is on 134.5 kHz with 3dB bandwidth of 9 kHz (Q=15 I know is a bit to high..) so carried out some tests on 134 kHz (of course on the dummyload) all without guard circuit 1st test xfmr 7T/19T (Ae197mm² R50 mat T38): 2Wout @10Vdc; 6,5 Wout@20Vdc; 13,7Wout@30Vdc stable.. @40Vdc after a quick peak the power slowly goes down till below 1W! 2nd test I had still on hands the previous xfmr 5T/12T (Ae197mm² same core as 1st test) so was worth to make a trial... same trend :-( for Vdc> 30V after a first peak... it goes down. I had another core available with different material (N30, Ae 154mm² R58) so I prepared a new xfmr with this core 7T/14T: 1,4Wout@10Vdc; 4,6Wout@20Vdc; 9,2Wout@30Vdc .... at 40Vdc a short burst with almost 15Wout and then down down down... :-(((((( I noticed a difference in comparison to your project: you connected the + and - rails to ground via 10nF and here I used 100nF caps could it explain this behaviour? 73 Marco ----Messaggio originale---- Da: marcocadeddu@tin.it Data: 1-giu-2017 22.20 A: Ogg: R: Re: Re: Re: LF: Re: I: Fw: For today the FETs survived... that was also my thought.. but they run at room temperature: the resonance is obtained with 4 polyesther 2200 pF 2000 Vdc caps. the classic boxes 25x15x5mm Marco ---- Messaggio originale---- Da: andy.g4jnt@gmail.com Data: 1-giu-2017 22.03 A: Ogg: Re: Re: Re: LF: Re: I: Fw: For today the FETs survived... If the conditions change as the PA is operating, it looks like capacitors heating up and changing its value. I can't think of any other component that will change with dissipation / heating. What type of capacitor are you using in the tank? Andy On 1 June 2017 at 19:59, marcocadeddu@tin.it wrote: > anybody has good ideas for a replacement hobby?? fishing? growing > flowers? > > Andy: the suggestion of try without the guard circuit revealed that > some effects in this area are present. > > I left the guard coil in place (I'm a bit lazy...) and disconnected > simply the 2 wires from the rectifier bridge. > The output improve of about 4dB with Vdd from 10 to 30V, the output is > stable up to 20Vdd, on 30V it show a peak of 16W, then the output > starts to decrease till a couple of watts :-( this happens also at 40 > and 50V. > The resonance of the output LC (with the guard coil open) shifts from > 137 to 140 kHz and the bandwidth decreases from 20kHz to 10 kHz. > > I need a long weekend of meditation... > 73 Marco IK1HSS > > > ----Messaggio originale---- > Da: marcocadeddu@tin.it > Data: 31-mag-2017 21.05 > A: > Ogg: R: Re: Re: LF: Re: I: Fw: For today the FETs survived... > > Andy.. you are almost better than online help desks :-D > > yes the guard circuit is on place but no current is flowing toward the > PA, testing disconnetting it needs just to warm up the iron ;-) > > the PS should > provide enough juice for 1200W input and the IRF460A are rated for 20A > @ 25°C (13A @ 100°C) so.. I admit it would like to give a try ;-) > > I don't guess the core is saturating specially at this power level > where rms is only 22V, the core is 50mm OD and has 195,7 mm²Ae: if I > am > not totally wrong B should be < 0,03T @50V with 7 turns on the primary > > Will tru to disconnect the guard circuit just in case the squirrel is > running in its cage ;-) > > Thanks again for assistence > > Marco IK1HSS > > > > ----Messaggio originale---- > Da: andy.g4jnt@gmail.com > Data: 31-mag-2017 20.39 > A: > Cc: > Ogg: Re: Re: LF: Re: I: Fw: For today the FETs survived... > > 7:19 turns (assuming 50R output) means you have a load resistance of > 6.8 > ohms which for 180V DC (81 V RSM fund sine) is nearly 1kW I don't > think > you really mean to go that extreme do you? 13 ohms is more > realistic. > > As for the tank resonance changing as power increases, that is very > wrong. > I wonder if the transformer is saturating. Not sure of your core Ae, > but > lets assume 200mm square, a core of about 16mm diameter. > > V = 4.44.F.N.A.B Plugging in 137kHz 7 turns, 200 mm^2 and a Bmax of > 0.1 > that suggests 85V RMS. > Which is exactlyly what you have. I suggest more primary turns . > Before > a transformer ratio of 1:2 was suggested, for Rload = 13 ohms > > Is the guard circuit in place ? Don't forget, it has to be > customised > to > you exact currents and coil Q. Get teh PA operating to its proper > settings > foirst - that you can do at low voltage power, it scales perfectly. > Only > when it it working properly can you add and set up the guard circuit. > > When I did teh 700W PA, I had a complete workign (albeit unreliable) > unit > before even thinking of teh guard circuitry. > > Andy > > > > > > On 31 May 2017 at 18:50, marcocadeddu@tin.it > wrote: > > > Hi Andy... me again... > > > > I was so curious to see what could happen thatI had a very quick > > dinner and connected all, but... > > > > now the output xfmr has 7T/19T here my > > readings/calculations: > > (see attached picture) > > again the power increase from 10 to 30Vcc then from 30 to 50Vcc after > > an initial burst it start to fall down.. > > I checked also the resonance of the LC: till 30Vcc is tuned on 137 > kHz > > with a 3dB bandwidth of 20 kHz, when I move to 40 and 50Vcc the > > "maximum" output shifts to 165 kHz... > > > > mumble mumble > > > > I tempted to have roasted FETs for dessert and see what happens at > > 180V! > > > > Marco, IK1HSS > > > > > > ----Messaggio originale---- > > Da: andy.g4jnt@gmail.com > > Data: 30-mag-2017 23.50 > > A: > > Cc: > > Ogg: Re: LF: Re: I: Fw: For today the FETs survived... > > > > I've just looked again at the circuit diagram you sent - on there the > > values are different from your statement in the email. It shows > > primary 5 > > turns, secondary 12 turns so a load resistance in the order of 9 ohms > > which > > is rather low if you are intending a Vdd of 180V - but closer to the > > ideal > > Rl > > > > The tank components have a reactance of 130 ohms which is too high a > Q > > is > > used with that 9 ohms Rload, You should be aiming for a Q in the > region > > of > > 6. > > > > Even with the optimum load R of 13 ohms described last time for 500 > > Watts > > from 180V rail the resulting Q of 10 is a bit too high - you will end > > up > > with high voltage and critical tuning > > > > Andy G4JNT > > > > On 29 May 2017 at 19:07, Andy Talbot wrote: > > > > > Yes. > > > As you'll see in my original write up, I originally forgot that the > > peak > > > of the fundamental sine component of a square wave is GREATER than > > the peak > > > by a factor of 4 / pi and initially my PA delivered a lot more > power > > (1.6 > > > times) than it was supposed to. > > > > > > So if the square wave has a peak value of 1, its fundamental sine > > > component has a peak value of 4/pi or around 1.27. The RMS of the > > > resulting sine is SQRT(2) less than this giving a Peak square to > RMS- > > sine > > > ratio of 0.9.. If you specifye peak-peak of the square wave, a > > further > > > factor of 2 applies, leading to the 0.45 ratio described before. > > > > > > Incidentally, this same ratio appears in that equation for flux > in > a > > > magnetic code, V = 4.44.F.N.A.B > > > The magic number 4.44 is actually SQRT(2) * pi and comes about > > from > > > the same sort of sine to square transform. > > > > > > Andy > > > > > > On 29 May 2017 at 18:48, marcocadeddu@tin.it > > wrote: > > > > > >> > > >> uhuh... a slightly silly misleading assumption... Vdc are the same > > of > > >> Vrms before FETs make their work! > > >> > > >> Thank you Andy for pointing out it!! > > >> With this approach calculation changes a bit and probably with the > > >> right Xfmr the PA can give higher satisfaction :-) > > >> > > >> Hopefully the FETs will survive and this time I'm ready to burnout > > the > > >> antenna hi > > >> > > >> Will keep you both updated, thank you once more Andy > > >> > > >> 73 Marco, IK1HSS > > >> ----Messaggio originale---- > > >> Da: andy.g4jnt@gmail.com > > >> Data: 28-mag-2017 21.18 > > >> A: "marcocadeddu@tin.it", > > >> > > >> Cc: > > >> Ogg: LF: Re: I: Fw: For today the FETs survived... > > >> > > >> First thing I noticed is that your turns ratio on the output > > >> transformer > > >> doesn't look right. > > >> You quote "* ... with primary winding of 15 turns and secondary of > > 12 > > >> turns...*" > > >> > > >> 180V DC in a half bridge is 180V peak-peak square wave. > > >> The fundamental sine part of that is 4/pi * 180 = 229V pk-pk > > >> so is 229V /[2.SQRT(2)] = 81V RMS > > >> > > >> To a good approximation RMS(fund) from a half bridge is Vrms > (fund) > = > > >> 0.45VDC > > >> > > >> For 500 Watts out, Rload = 81 ^ 2 / 500 = 13 ohms > > >> > > >> So to match to 50 ohms you need a turns ratio of SQRT(50/13) = > 1.9: > > >> 1 so > > >> call it 2:1 Keeping 12 turns on the secondary means you need 6 > > turns > > >> on > > >> the primary > > >> > > >> When operating at reduced voltage, the power out will vary exactly > > as > > >> the > > >> square of the voltage. > > >> Recalculating from first principles for a 12V supply: > > >> > > >> 12V DC = 12V pk-pk = 12 / [2.SQRT(2)] * 4/pi = 5.4V RMS > > (fundamental) > > >> in 13 ohms should give 5.4^2/13 = 2.2 Watts > > >> > > >> check using ratio of voltages, squared : > > >> > > >> (12V/180V) ^ 2 * 500W = 2.2 Watts which is the same as above. > > >> QED > > >> > > >> Your 15:12 ratio result sin a load impedance of (15/12)^2 * 50 = > 78 > > >> ohms > > >> > > >> At 40V DC == 18V RMS(fund) that will give 18^2/78 = 4.1 watts > which > > is > > >> actually LESS that you are seeing - the 2* discrepancy is odd, but > > the > > >> low > > >> power is in the area of what you measured.. > > >> > > >> Andy G4JNT > > >> > > >> > > >> > > >> On 28 May 2017 at 19:34, marcocadeddu@tin.it > > >> wrote: > > >> > > >> > Hi Chris, > > >> > > > >> > I tried to post this message on the reflector but apparently I > had > > no > > >> > success.. > > >> > As promised I keep you updated but as you can read in the > > >> > attachment the first trials were not enocouraging... > > >> > Andy, may I ask you to read my report? your interpretation and > > >> > suggestion are welcome! > > >> > > > >> > 73, Marco IK1HSS > > >> > > > >> > > > >> > -----Original message----- > > >> > > > >> > From: "marcocadeddu@tin.it" marcocadeddu@tin.it > > >> > Date: Sun, 28 May 2017 17:01:33 +0200 > > >> > To: rsgb_lf_group@blacksheep.org > > >> > Subject: For today the FETs survived... > > >> > > > >> > Hi LF, > > >> > > > >> > hope that also the toroids of Chris survived! > > >> > My FETs survived, but they are not working as expected :-( > > >> > Attached the report on my attempt to duplicate the half bridge > of > > >> > Andy.. > > >> > Has anyone suggestions before I try to cook all connecting to > the > > >> > 180Vdc supply? > > >> > > > >> > Thank you > > >> > 73 Marco IK1HSS > > >> > > > >> > > > >> > -- > > >> > This message has been scanned by E.F.A. Project and is believed > to > > be > > >> > clean. > > >> > > > >> > > > >> > > > >> > > > >> > > > >> > > > >> > > > >> > ---------- Forwarded message ---------- > > >> > From: "marcocadeddu@tin.it" > > >> > To: > > >> > Cc: > > >> > Bcc: > > >> > Date: Sun, 28 May 2017 17:01:33 +0200 (CEST) > > >> > Subject: For today the FETs survived... > > >> > Hi LF, > > >> > > > >> > hope that also the toroids of Chris survived! > > >> > My FETs survived, but they are not working as expected :-( > > >> > Attached the report on my attempt to duplicate the half bridge > of > > >> > Andy.. > > >> > Has anyone suggestions before I try to cook all connecting to > the > > >> > 180Vdc supply? > > >> > > > >> > Thank you > > >> > 73 Marco IK1HSS > > >> > > > >> > > > >> > -- > > >> > This message has been scanned by E.F.A. Project and is believed > to > > be > > >> > clean. > > >> > > > >> > > > >> > > > >> > > > >> > > >> > > >> > > >> > > >> > > > > > > > > > > > > > > > > > >