From owner-freebsd-stable Mon Mar 13 16:56:11 2000 Delivered-To: freebsd-stable@freebsd.org Received: from alcanet.com.au (mail.alcanet.com.au [203.62.196.10]) by hub.freebsd.org (Postfix) with ESMTP id BE54337B5B7 for ; Mon, 13 Mar 2000 16:56:02 -0800 (PST) (envelope-from jeremyp@gsmx07.alcatel.com.au) Received: by border.alcanet.com.au id <115313>; Tue, 14 Mar 2000 11:55:43 +1100 Content-return: prohibited From: Peter Jeremy Subject: Re: Weirdest crash I ever saw... In-reply-to: ; from kris@hiwaay.net on Tue, Mar 14, 2000 at 08:24:52AM +1100 To: Kris Kirby Cc: blk@skynet.be, freebsd-stable@FreeBSD.ORG Message-Id: <00Mar14.115543est.115313@border.alcanet.com.au> MIME-version: 1.0 X-Mailer: Mutt 1.0i Content-type: text/plain; charset=us-ascii References: Date: Tue, 14 Mar 2000 11:55:42 +1100 Sender: owner-freebsd-stable@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On 2000-Mar-14 08:24:52 +1100, Kris Kirby wrote: >On Mon, 13 Mar 2000, Brad Knowles wrote: > >> > Two words: Isolation Transformer. Any decent electrical supply house should be able to sell you one. The larger elecronics components suppliers may also have them. (I suspect any names I give you won't be much use). >I do know that Sola makes some. Look toward the UPS vendors and power >systems vendors. ... > The terrible side effect of the >isolation transformer (which in itself is a 1:1 transformer) is that it >always draws it's rated power, whether under load or not. I've never seen any that did this. A normal isolation transformer is just an ordinary transformer with 1:1 turns ratio. The input current and power are proportional to the output current and power (plus a small magnetizing current). If you're talking about the older ferro-resonant constant-voltage transformers, they drew a constant _current_ and the input phase angle changed with load. They were also fairly inefficient (something like 10% of the rated power turned into heat). Note that ferro-resonant transformers have an output waveform close to a square-wave. They also current-limit at close to their rated output current - which means loads with large inrush currents will cause serious voltage droop. Finally, the output voltage is quite frequency sensitive - don't try to use a 50Hz unit at 60Hz or vice versa. Peter To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message