Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by klubnl.pl (8.14.4/8.14.4/Debian-8+deb8u2) with ESMTP id w44Gr161013147 for ; Fri, 4 May 2018 18:53:03 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1fEdoc-00087Q-21 for rs_out_1@blacksheep.org; Fri, 04 May 2018 17:44:14 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1fEdoD-00087F-6P for rsgb_lf_group@blacksheep.org; Fri, 04 May 2018 17:43:49 +0100 Received: from mail-wm0-x22e.google.com ([2a00:1450:400c:c09::22e]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1fEdo8-0006PM-7e for rsgb_lf_group@blacksheep.org; Fri, 04 May 2018 17:43:47 +0100 Received: by mail-wm0-x22e.google.com with SMTP id j4so4989664wme.1 for ; Fri, 04 May 2018 09:43:43 -0700 (PDT) X-DKIM-Result: Domain=gmail.com Result=Good and Known Domain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to; bh=5i30MgyzYVLDU3+ZQ2xyVz7O3v9zAh8PDZLJPocd8jM=; b=iQXq56gyiCnnyJ1OWJBoxsKPJa91JBueJUZddVcD5ZiY7uJqbNSfCw9xMe+zPrrKzY qKEtpIP7zzQfsq6Iy1wgh2CeipSGa/9F8g6oYpPTW22Lrs1lgfUdqfyIxsJI8J5WFp0n Mfg8jOqbukuo4P0yGkYEe0RlhoNYDWE1Dg5t/+/3k007A1ibWY1a2lXvexizn8Hb1DkM YZ5MdcaKUKNftagm2qfCGd066vMuq5a1lVVPshkRAuaBqiNLFiS9zFCvBdPoA/5nVcr+ 3J/PxydzkHyoRsEv75fSXFvOwIbvVj3QOVmDXdJnO/hZgaPu04ygbnAGfn4fg8Vj0KvL Zd5Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to; bh=5i30MgyzYVLDU3+ZQ2xyVz7O3v9zAh8PDZLJPocd8jM=; b=rtiK+KcKPKZt454KzrobmDQ1lrfC4IrtKWm+DY8Pe0DsjcFfyl3MJcbmAuJZ940Jhq wmpvCbpXqe+HeDr1N5eObZzihH9V+21+tuInj4JlQfCFEbC1BlBvTr5cKanpmcqX1VPG EB6wPtx68IOfRuwI1rex+0I+woHRev1MqTQsaxhe5Htzv35RaiyE5YDnIXin3RsOu3j5 8xZBQ8J1mf3cAvhSuSl99L30HWP/gKLoIFvPeQuiQg5uYrUwliwIe772tvLpuJOarejM qW4VKcW7gp79cuUP0oF/jSfcvR3dTws7GpD45lRnFDSukUYckH7WsJvLHWgTdpLakR0V Qo/Q== X-Gm-Message-State: ALQs6tDLNShpI0kgB1ill/YF1v8Q0UduiRd2rogubwt8MF6dNR4Jskt5 oamBANvxGS4gVAhmVEXugYrdQWiXXBCl71kdIQI= X-Google-Smtp-Source: AB8JxZpDEC/pLVekzdwBT0sPULxrliCrR3/+rv1XRnHF3sKM8/5Esgn7HwPCP3IelAmli5MM6DcAE4/nL4vTj9u4QA8= X-Received: by 2002:a50:cc45:: with SMTP id n5-v6mr20107932edi.11.1525452223163; Fri, 04 May 2018 09:43:43 -0700 (PDT) MIME-Version: 1.0 Received: by 10.80.159.130 with HTTP; Fri, 4 May 2018 09:43:42 -0700 (PDT) In-Reply-To: References: <376794419.20180503144640@gmail.com> From: Andy Talbot Date: Fri, 4 May 2018 17:43:42 +0100 Message-ID: To: LineOne X-Spam-Score: 1.8 (+) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: If you stack cores, you just add the core areas together. There may be a bit of leakage inductance- it may be noticeable, it may not. Tape, gapes between them all add to leakage inductance, but doubt it'll be all that much. [...] Content analysis details: (1.8 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (andy.g4jnt[at]gmail.com) 0.0 HTML_MESSAGE BODY: HTML included in message 0.6 URIBL_SBL Contains an URL's NS IP listed in the Spamhaus SBL blocklist [URIs: n1bug.com] 0.1 URIBL_SBL_A Contains URL's A record listed in the Spamhaus SBL blocklist [URIs: n1bug.com] 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid 1.0 FREEMAIL_REPLY From and body contain different freemails X-Scan-Signature: 640db27bf4e79f20c339a3df4106c3a6 Subject: Re: LF: How can you tell if a Class D amp output transformer is starting to saturate? Content-Type: multipart/alternative; boundary="000000000000e23071056b6405ec" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_20_30,HTML_MESSAGE 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 --000000000000e23071056b6405ec Content-Type: text/plain; charset="UTF-8" If you stack cores, you just add the core areas together. There may be a bit of leakage inductance- it may be noticeable, it may not. Tape, gapes between them all add to leakage inductance, but doubt it'll be all that much. Iron powder is an interesting situation as it has gaps inherent and built in. The same equation applies but our inductance and ur are so much less that probably you'll need far more turns to get a workable inductance than you'd ever need to get saturation down. Bsat for iron is higher, but different rules apply and to prevent losses you probably have to keep it way down. Shouldn't be using iron dust for transformers simply because you need so many turns to get L high enough to be insignificant, but some people do Andy www.g4jnt.com On 4 May 2018 at 12:29, N1BUG wrote: > Thanks Andy. > > I've added a page on this in my handwritten notebook. > > I do have some related questions which go beyond what Chris asked about. > > What about stacked cores? If we stack three cores, each having a > cross sectional area of 1.58 cm^2, does it become 4.74 cm^2? Do the > cores have to be in physical contact with each other? What if each > is first wrapped with insulating tape, then they are stacked? > > Finally, this dealt with ferrite cores. What about iron powder core > saturation? > > Paul > > > > On 05/03/2018 12:05 PM, Andy Talbot wrote: > > The peak of the fundamental sine component in a square wave is 4/pi > > times the square wave amplitude (yes, it is bigger). The RMS of > > the sine is Peak / SQRT(2) . Take the two together and the RMS of > > your sine is therefore 0.9 * Peak of the square wave > > > > So if you had a Vdd of 50V you would have 45V rms across each half > > of the winding, or 90V rms across the two halves. Which answers > > your other question > > > > Actually, thinking about what I've just said, you are putting the > > square wave though the transformer, not a sine. So in that case > > you have a bit more leeway in that it can go to the same peak value > > as the sine would have given you. > > > > Unless I'm building SMPSUs, I don't put square waves though > > transformers in transmitters - teh RF is always filtered > > beforehand. There is an equivalent equation for square waves and > > used in SMPSU design, it is V.t = N.A.B Now V is input > > voltage, t is the on-time , and N.A.B as before > > > > And yes, your area is correct. 1.58cm^2 = 0.000158m^2 > > > > Andy > > www.g4jnt.com > > > > > > On 3 May 2018 at 16:36, N1BUG > > wrote: > > > > I am still not sure whether I am using that equation correctly. > > > > Chris, if you will forgive me for tagging along on your post, I'm > > trying to get this equation sorted in my head. Put no faith in > > anything I say with regard to this! ;-) > > > > Andy, could you please check me out on this? > > > > Let's use the case Chris asks about as an example. > > > > Suppose I want to calculate the maximum RMS voltage to stay out of > > saturation. > > > > The manufacturer of the core states its Ae (equivalent cross > > sectional area) is 1.58 cm^2. I believe that works out to > > 0.000158 m^2. > > > > F = 137000 > > > > I do not know if I should be using 4 turns or 8 turns for the > > primary. It's 4+4. I will assume 8. > > > > Vrms = 4.44 * 137000 * 8 * 0.000158 * 0.1 > > > > Vrms = ~77V > > > > Does that look right? > > > > As for practical application I have no idea what this means. The > > equation uses Vrms but we're talking about something closer to a > > square wave than sine wave. But then it's not really a square wave > > either... > > > > Paul > > > > > > > > On 05/03/2018 10:00 AM, Andy Talbot wrote: > > > By measuring the voltage across the winding using a scope, then > > > seeing what Bmax is using teh equation > > > > > > Vrms = 4.44.F.N.A.B > > > > > > F Hz N turns A core cross-sectional area in metres^2 B > tesla > > > > > > If B works out higher than about 0.1 for a ferrite core, then you > > > are approaching saturation > > > > > > Andy > > > www.g4jnt.com > > > > > > > > > On 3 May 2018 at 14:46, Chris Wilson dead.fets@gmail.com> > > > >> wrote: > > > > > > > > > > > > Hello LF'ers > > > > > > In say a W1VD power amp, or in general, how can you test if > the > > > output transformer is > > > starting to saturate please? Thanks. > > > > > > http://www.w1vd.com/137-500-KWTX.html > > > > > > > > > > > > > > > > > > > -- > > > Best regards, > > > Chris mailto:dead.fets@gmail.com > > > > > > > --000000000000e23071056b6405ec Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
If you stack cores, you just add the core areas together.= =C2=A0 =C2=A0There may be a bit of leakage inductance- it may be noticeable= , it may not.
Tape, gapes between them all add to leakage inductance, b= ut doubt it'll be all that much.

Iron powder i= s an interesting situation as it has gaps inherent and built in.=C2=A0 The = same equation applies but our inductance and ur are so much less that proba= bly you'll need far more turns to get a workable inductance than you= 9;d ever need to get saturation down.=C2=A0 =C2=A0 Bsat for iron is higher,= but different rules apply and to prevent losses you probably have to keep = it way down.
Shouldn't be using iron dust for transformers si= mply because you need so many turns to get L high enough to be insignifican= t, but some people do

=
=
Andy<= div>
<= /div>
On 4 May 2018 at 12:29, N1BUG <paul@n1bug.com<= /a>> wrote:
Thanks Andy.

I've added a page on this in my handwritten notebook.

I do have some related questions which go beyond what Chris asked about.
What about stacked cores? If we stack three cores, each having a
cross sectional area of 1.58 cm^2, does it become 4.74 cm^2? Do the
cores have to be in physical contact with each other? What if each
is first wrapped with insulating tape, then they are stacked?

Finally, this dealt with ferrite cores. What about iron powder core
saturation?

Paul



On 05/03/2018 12:05 PM, Andy Talbot wrote:
> The peak of the fundamental sine component in a square wave is 4/pi > times the square wave amplitude (yes, it is bigger).=C2=A0 =C2=A0The R= MS of
> the sine is Peak / SQRT(2) .=C2=A0 Take the two together and the RMS o= f
> your sine is therefore 0.9 * Peak of the square wave
>
> So if you had a Vdd of 50V you would have 45V rms across each half
> of the winding, or 90V rms across the two halves.=C2=A0 Which answers<= br> > your other question
>
> Actually, thinking about what I've just said, you are putting the<= br> > square wave though the transformer, not a=C2=A0 sine.=C2=A0 So in that= case
> you have a bit more leeway in that it can go to the same peak value > as the sine would have given you.
>
> Unless I'm building SMPSUs, I don't put square waves though > transformers in transmitters - teh RF is always filtered
> beforehand.=C2=A0 =C2=A0There is an equivalent equation for square wav= es and
> used in SMPSU design,=C2=A0 it is=C2=A0 =C2=A0V.t =3D N.A.B=C2=A0 =C2= =A0 Now V is input
> voltage,=C2=A0 t is the on-time , and N.A.B as before
>
> And yes, your area is correct.=C2=A0 1.58cm^2 =3D 0.000158m^2
>
> Andy
> = www.g4jnt.com <http://www.g4jnt.com>
>
>
> On 3 May 2018 at 16:36, N1BUG <pa= ul@n1bug.com
> <mailto:paul@n1bug.com>>= ; wrote:
>
>=C2=A0 =C2=A0 =C2=A0I am still not sure whether I am using that equatio= n correctly.
>
>=C2=A0 =C2=A0 =C2=A0Chris, if you will forgive me for tagging along on = your post, I'm
>=C2=A0 =C2=A0 =C2=A0trying to get this equation sorted in my head. Put = no faith in
>=C2=A0 =C2=A0 =C2=A0anything I say with regard to this! ;-)
>
>=C2=A0 =C2=A0 =C2=A0Andy, could you please check me out on this?
>
>=C2=A0 =C2=A0 =C2=A0Let's use the case Chris asks about as an examp= le.
>
>=C2=A0 =C2=A0 =C2=A0Suppose I want to calculate the maximum RMS voltage= to stay out of
>=C2=A0 =C2=A0 =C2=A0saturation.
>
>=C2=A0 =C2=A0 =C2=A0The manufacturer of the core states its Ae (equival= ent cross
>=C2=A0 =C2=A0 =C2=A0sectional area) is 1.58 cm^2. I believe that works = out to
>=C2=A0 =C2=A0 =C2=A00.000158 m^2.
>
>=C2=A0 =C2=A0 =C2=A0F =3D 137000
>
>=C2=A0 =C2=A0 =C2=A0I do not know if I should be using 4 turns or 8 tur= ns for the
>=C2=A0 =C2=A0 =C2=A0primary. It's 4+4. I will assume 8.
>
>=C2=A0 =C2=A0 =C2=A0Vrms =3D 4.44 * 137000 * 8 * 0.000158 * 0.1
>
>=C2=A0 =C2=A0 =C2=A0Vrms =3D ~77V
>
>=C2=A0 =C2=A0 =C2=A0Does that look right?
>
>=C2=A0 =C2=A0 =C2=A0As for practical application I have no idea what th= is means. The
>=C2=A0 =C2=A0 =C2=A0equation uses Vrms but we're talking about some= thing closer to a
>=C2=A0 =C2=A0 =C2=A0square wave than sine wave. But then it's not r= eally a square wave
>=C2=A0 =C2=A0 =C2=A0either...
>
>=C2=A0 =C2=A0 =C2=A0Paul
>
>
>
>=C2=A0 =C2=A0 =C2=A0On 05/03/2018 10:00 AM, Andy Talbot wrote:
>=C2=A0 =C2=A0 =C2=A0> By measuring the voltage across the winding us= ing a scope, then
>=C2=A0 =C2=A0 =C2=A0> seeing what Bmax is using teh equation
>=C2=A0 =C2=A0 =C2=A0>
>=C2=A0 =C2=A0 =C2=A0> Vrms =3D 4.44.F.N.A.B
>=C2=A0 =C2=A0 =C2=A0>
>=C2=A0 =C2=A0 =C2=A0> F Hz=C2=A0 =C2=A0 =C2=A0N turns=C2=A0 =C2=A0A = core cross-sectional area in metres^2=C2=A0 =C2=A0 B tesla
>=C2=A0 =C2=A0 =C2=A0>
>=C2=A0 =C2=A0 =C2=A0> If B works out higher than about 0.1 for a fer= rite core, then you
>=C2=A0 =C2=A0 =C2=A0> are approaching saturation
>=C2=A0 =C2=A0 =C2=A0>
>=C2=A0 =C2=A0 =C2=A0> Andy
>=C2=A0 =C2=A0 =C2=A0> www.g4jnt.com <http://www.g4jnt.com> <<= a href=3D"http://www.g4jnt.com" rel=3D"noreferrer" target=3D"_blank">http:/= /www.g4jnt.com>
>=C2=A0 =C2=A0 =C2=A0>
>=C2=A0 =C2=A0 =C2=A0>
>=C2=A0 =C2=A0 =C2=A0> On 3 May 2018 at 14:46, Chris Wilson <dead.fets@gmail.com <mailto:dead.fets@gmail.com>
>=C2=A0 =C2=A0 =C2=A0> <mailto:dead.fets@gmail.com <mailto:dead.fets@gmail.com>>> wrote:
>=C2=A0 =C2=A0 =C2=A0>
>=C2=A0 =C2=A0 =C2=A0>
>=C2=A0 =C2=A0 =C2=A0>
>=C2=A0 =C2=A0 =C2=A0>=C2=A0 =C2=A0 =C2=A0Hello LF'ers
>=C2=A0 =C2=A0 =C2=A0>
>=C2=A0 =C2=A0 =C2=A0>=C2=A0 =C2=A0 =C2=A0In=C2=A0 say a W1VD power a= mp, or in general, how can you test if the
>=C2=A0 =C2=A0 =C2=A0>=C2=A0 =C2=A0 =C2=A0output transformer is
>=C2=A0 =C2=A0 =C2=A0>=C2=A0 =C2=A0 =C2=A0starting to saturate please= ? Thanks.
>=C2=A0 =C2=A0 =C2=A0>
>=C2=A0 =C2=A0 =C2=A0>=C2=A0 =C2=A0 =C2=A0http://www.w1vd= .com/137-500-KWTX.html
>=C2=A0 =C2=A0 =C2=A0<http://www.w1vd.com/137-500-KW= TX.html>
>=C2=A0 =C2=A0 =C2=A0>=C2=A0 =C2=A0 =C2=A0<http://www.= w1vd.com/137-500-KWTX.html
>=C2=A0 =C2=A0 =C2=A0<http://www.w1vd.com/137-500-KW= TX.html>>
>=C2=A0 =C2=A0 =C2=A0>
>=C2=A0 =C2=A0 =C2=A0>
>=C2=A0 =C2=A0 =C2=A0>
>=C2=A0 =C2=A0 =C2=A0>=C2=A0 =C2=A0 =C2=A0--
>=C2=A0 =C2=A0 =C2=A0>=C2=A0 =C2=A0 =C2=A0Best regards,
>=C2=A0 =C2=A0 =C2=A0>=C2=A0 =C2=A0 =C2=A0=C2=A0Chris=C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 mailto:dead.fets@gmail.com &= lt;mailto:dead.fets@gmail.com>= ;
>=C2=A0 =C2=A0 =C2=A0>=C2=A0 =C2=A0 =C2=A0<mailto:dead.fets@gmail.com <mailto:dead.fets@gmail.com>>


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