Date: Tue, 14 Mar 2000 11:55:42 +1100 From: Peter Jeremy <peter.jeremy@alcatel.com.au> To: Kris Kirby <kris@hiwaay.net> Cc: blk@skynet.be, freebsd-stable@FreeBSD.ORG Subject: Re: Weirdest crash I ever saw... Message-ID: <00Mar14.115543est.115313@border.alcanet.com.au> In-Reply-To: <Pine.BSF.4.10.10003131518340.29922-100000@barricuda.bsd.nws.net>; from kris@hiwaay.net on Tue, Mar 14, 2000 at 08:24:52AM %2B1100 References: <v04220814b4f307e1b3bf@[195.238.24.123]> <Pine.BSF.4.10.10003131518340.29922-100000@barricuda.bsd.nws.net>
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On 2000-Mar-14 08:24:52 +1100, Kris Kirby <kris@hiwaay.net> 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
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