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 can't find these tubes on the market anymore. The last time we
purchased them was in 2007 and they had to be manufactured special by
Philips. We're thinking of moving to regular T8 tubes with a DC inverter
ballast. Anyone here know more about why these are not made anymore or
have any ideas where to look?

Thanks,
Mike

https://www.assets.lighting.philips.com/is/content/PhilipsLighting/
comf2571-pss-global

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.

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

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. I am in contact with several companies
that supply low voltage LED lighting for rail vehicles as a parallel path.

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

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.