Envelope-to: dave@picks.force9.co.uk Delivery-date: Wed, 14 Sep 2005 15:23:21 +0100 Received: by pih-mxcore10.plus.net with spam-scanned (PlusNet MXCore v2.00) id 1EFYAS-0007L1-GO for dave@picks.force9.co.uk; Wed, 14 Sep 2005 15:23:21 +0100 Received: from post.thorcom.com ([193.82.116.20]) by pih-mxcore10.plus.net with esmtp (PlusNet MXCore v2.00) id 1EFYAS-0007Kl-Bg for dave@picks.force9.co.uk; Wed, 14 Sep 2005 15:23:20 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1EFYAC-0002iY-QX for rs_out_1@blacksheep.org; Wed, 14 Sep 2005 15:23:04 +0100 Received: from [193.82.59.130] (helo=relay2.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1EFYAC-0002iP-5c for rsgb_lf_group@blacksheep.org; Wed, 14 Sep 2005 15:23:04 +0100 Received: from newbox.tcp.net.uk ([195.80.0.243]) by relay2.thorcom.net with esmtp (Exim 4.51) id 1EFYpc-0002XM-FK for rsgb_lf_group@blacksheep.org; Wed, 14 Sep 2005 16:05:56 +0100 Received: from [212.248.140.50] ([212.248.140.50]) by newbox.tcp.net.uk (8.12.7/8.12.7) with ESMTP id j8EENUCs007356 for ; Wed, 14 Sep 2005 15:23:32 +0100 (BST) Received: from 127.0.0.1 (AVG SMTP 7.0.344 [267.10.21]); Wed, 14 Sep 2005 15:22:54 +0100 Message-ID: <000c01c5b937$cbdc9d20$045bfea9@d4f8d8> From: "Andy Talbot" To: rsgb_lf_group@blacksheep.org References: <000601c5b922$0e59f410$268cf8d4@standalone> <000601c5b932$848f14c0$87468351@Main> Date: Wed, 14 Sep 2005 15:22:53 +0100 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Mime-Version: 1.0 X-TCP-MailScanner-Information: Please visit www.tcp.co.uk for more information X-TCP-MailScanner: Found to be clean X-TCP-MailScanner-From: actalbot@southsurf.com Subject: LF: Re: Re: Current Transformers (off topic, but expertise probably here) Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=iso-8859-1; format=flowed 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-PN-SpamFiltered: by PlusNet MXCore (v2.00) Rik - Oops. typing mistake there - the 0.3V came from 5 turns put on to test, so the 4000 turn primary was correct. Alan - I don't see how a rule of thumb can give a fixed number of tuurns per volt. the critical parameter for sizing a transformer is based on cross-sectional area, and for a sinusoidal device V = 4.44.F.N.A.B. I use this equation a lot for ferrite (and its SMPSU varient, V.t = N.A.B) and it works fine, but not sure what sort of B is alloed in iron - for this small transformer it looks as if Bcould be up to 1 Tesla pk. Andy -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.10.21/96 - Release Date: 2005-09-10