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From: "Phil Allison"
References: <4LPj9.firstname.lastname@example.org> <email@example.com>
Subject: Re: Halogen bulb drive
X-Newsreader: Microsoft Outlook Express 5.50.4522.1200
Date: Wed, 25 Sep 2002 12:31:43 +1000
NNTP-Posting-Date: Wed, 25 Sep 2002 12:20:37 EST
Organization: Telstra BigPond Internet Services (http://www.bigpond.com)
"amdx" wrote in message
> > 110/240 volt halogens are not so common - and since the OP >made no
> special mention of them or having a 110/240 DC supply >available then it
> seems a non issue.
> I came in the middle of a repair job, the power supply for four
> halogen bulbs had been discarded. A transformer was installed
> and failed as did the second one.
> I enter here--I note the bulbs are rated 13.8v 25w, quickly calculate
> bulbs draw about 2 amps each. All four would be about 8 amps and the
> existing (defective) transformer is rated 30va. So--- after a few
> it seems the original (discarded)power supply was small, I think it may
> been a switching
> power supply. If my assumption is correct, the bulbs were using DC . I
> don't see any cheap 13.8v 8 amp switching power supplies,
> so I decide to put a transformer on the display, and run them with
** Transformers for use with low voltage halogens (di-chroics) are
commonly electronic these days. They deliever high frequency AC (40 - 50 kHz
, often with amplitude modulation ) to the lamps so cable runs have to be
kept short to avoid losses at this frequency.
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