Re: Philips TL-S bulbs

On Wed, 10 Apr 2024 17:16:42 +0100, Liz Tuddenham wrote:

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).

That's actually a good point.  I don't think the maintenance people tried
that.  I'll go and check if they still have the bad bulbs.  Thanks.