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From: liz@poppyrecords.invalid.invalid (Liz Tuddenham)
Newsgroups: sci.electronics.design
Subject: Re: Philips TL-S bulbs
Date: Wed, 10 Apr 2024 17:16:42 +0100
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Mike Mocha <mocha@mailexcite.com> wrote:

> On Wed, 10 Apr 2024 08:44:52 +0100, Liz Tuddenham wrote:
> 
> > Mike Mocha <mocha@mailexcite.com> wrote:
> > 
> >> Hey all,
> >> 
> >> I have an old rail car design that used ballast-free florescent tubes
> >> in a 600 VDC circuit; bulbs used in series with power resistors, the
> >> circuit basically put 100 VDC or 60 VDC over each bulb.  There's no AC
> >> source on the car.
> > 
> > I think those tubes needed special switches to reverse the polarity each
> > time they were switched on.  This was to prevent darkening of one end of
> > the tube after a few hours, caused by migration of the mercury.  You may
> > have to replace the switchgear if you fit inverter-powered lamps.
> > 
> > If you contact a tramcar manufacturer, they should be able to put you in
> > touch with some companies that supply modern lighting equipment for 600
> > VDC.
> 
> You might be correct about this in terms of a good practice, but in the
> design I'm dealing with this is not the case, and thus possibly the reason
> so many of the tubes burned out. 

Are you sure they have, in fact, burnt out?  If they have gone black at
one end, that is most likely because of the mercury migration problem.
Reversing the polarity should restore them for a short while until the
mercury migrates the other way.

There is a lot of information about this in the Philips Technical
Review, I remember reading it but can't remember the date (it might have
been in the 1930s).

-- 
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk