Author Topic: Fluorescent lighting on 25 cycle current  (Read 9839 times)
hannahs lights
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Re: Fluorescent lighting on 25 cycle current « Reply #15 on: April 19, 2015, 01:43:38 PM » Author: hannahs lights
Just a quick update I've since found out that London underground uses a system of 2 live tracks one at 440 volts and the other at 220 volts DC of course the traction motors are across both to get 660 volts but lighting and other smaller loads are on only one 220 volts side there for no additional volt dropping gear needed for the lights
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Medved
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Re: Fluorescent lighting on 25 cycle current « Reply #16 on: April 20, 2015, 01:42:24 AM » Author: Medved
That's interesting, but quite complex system: Two suppy rails...

Here the most common was to use either just series groups of mains incandescents (in 600V trams it were triplets, later replaced by series pairs of ~90cm 25W fluorescents with one resistive ballast for the pair; these are still in operation today) directly supplied from the traction power, later replaced by usually 24V battery backup system (supplied via either rotary, or later solid state converter system). The later is virtually the only system in use in vehicles designed past ~1980 or so.

And on railway cars was most common completely independent (battery backup) DC power system, supplied by a dedicated generator (dynamo in the older or alternator in not that old cars) from the car movement, so completely electrically separated from the traction power (and from other cars as well). Onlyin about last decade the power source is a HV feed cable (originally used just for the heating power, today used as well for the air conditionning and lighting as well) via a converter, the axle generators are disappearing.
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Re: Fluorescent lighting on 25 cycle current « Reply #17 on: May 25, 2015, 12:46:39 PM » Author: Solanaceae
I also thought that someone around here had a duel tap fluorescent ballast that worked with 25 or 60hz.
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randacnam7321
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Re: Fluorescent lighting on 25 cycle current « Reply #18 on: June 15, 2015, 06:02:22 AM » Author: randacnam7321
The reason for the dual traction supply rails is to prevent galvanic corrosion of tunnel lining walls and traction rails that might happen were they part of the current return path.  At least that is the justification that I have seen.
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Medved
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Re: Fluorescent lighting on 25 cycle current « Reply #19 on: June 19, 2015, 12:06:39 PM » Author: Medved
Normally the "running" tracks have to be insulated as well, as they are used for the traffic control system (detect train presence by the wheels shorting them), so even some voltage drop should not be any problem...

Maybe when the system was set up, they didn't know the trick with the center tapped transformers and AC based systems (the center tapped transformer collects the high traction current from both rails, while allows the rather low power detection current to be injected or picked up from the rails).
Once it is working and becomes a standard, it becomes extremely difficult to change the system to something else, even when that would be way more practical...
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Re: Fluorescent lighting on 25 cycle current « Reply #20 on: June 19, 2015, 12:48:38 PM » Author: Solanaceae
Also, do they use some sort of "sacrificial anode" made from zinc to spare the electrified parts like in boats?
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Medved
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Re: Fluorescent lighting on 25 cycle current « Reply #21 on: June 20, 2015, 06:50:48 AM » Author: Medved
Sacrificed anode works only without external field, it has too low voltage potential. Therefore the problems with DC tractions and not insulated rails: The connection faults on the rails tend to generate rather strong fields in the ground, either overpowering the sacrificial anodes, or shortening their life too much.

Well, a form of a sacrificial anode is even the Zinc coating on steel structures...
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kai
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Railways on 16 2/3 Hz « Reply #22 on: September 01, 2015, 04:49:33 PM » Author: kai
On the main railway the 25Hz (and most of the others low frequency) systems start to disappear

Is this really the case anywhere?

What I can describe is the situation in Germany, Austria and Switzerland, and I'm not aware of a different state of affairs in Norway: There are no plans whatsoever to replace the 16 2/3 Hz traction power system. It is also used for new projects. Back in the 60s it has been considered to use 50 Hz for new installations in both parts of Germany. These examinations came, completely independent from each other, both to the conclusion that it's simply not worth the operational hassle it would have introduced.

It must be considered here that using 50 Hz as traction power is not as straightforward as it appears to be, because you can not hook up a whole railway system on only one of the three phases. Thus insulated sections, with feeds spread over the three phases, must be designed. This makes the need for converters less of an issue than it appears to be, especially with todays solid-state technology where these are no longer big rotating machines.
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Medved
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Re: Fluorescent lighting on 25 cycle current « Reply #23 on: September 03, 2015, 02:31:49 PM » Author: Medved
The 50Hz is of no big trouble at all, the systems for transitioning phases are working well and are less complicated than the frequency changer converter.
Plus the 16.6667Hz system needs to use multi phase system as well, otherwise it tend to propagate the 16.667Hz into the 50Hz network (even rotary converters had suffered from that problem). So switching between phases should be solved even in the "16.67Hz area"...

The main problems is the design of many older vehicles, where the AC directly feeds the motors, these can not operate at 50Hz at all. The newer vehicles, using rectifiers, would have no problems with the frequency.
Plus other problem: The present 50Hz systems in Europe are 25kV. So to really transition to anything meaningful, it would mean increasing the voltage level as well. But that would mean completely new distribution system, as the present one won't be able to handle the 25kV.
Otherwise just changing the frequency and keeping the voltage would create "just another" railway system, so consuming a lot of money without the benefit of reducing the number of systems the vehicles shall support.

Today the 16.67Hz system is problematic for many other reasons: Transformers are about 4x heavier, what means way higher energy consumption mainly for the lighter high speed passenger units (those operate the best from the 3kV DC system, as that needs no transformer whatsoever and the rather low 3kV is of not that big problem, because the passenger vehicles do not need so high power levels like does e.g. the heavy cargo transport).


But the supply system is not the biggest obstacle, it is technically feasible to make a vehicle working on all power systems across the whole Europe (and majority of the new engines are made that way). The biggest problem is the variability of the safety  and communication systems, where to serve all systems used in Europe is simply not possible, because most of them need some transponder antennas in front of the first axle and all of them just won't fit there... The ECTS is supposed to solve that, but at this moment the ECTS is "just another system" to support.

And given how the railways are flexible in Europe, I think the earliest time when one single diesel engine could travel anywhere in the Europe, sufficing with the ECTS, won't be earlier than in 100 years from now. Because the railway authorities in the Europe are already for longer than 100 years arguing, which variant of the automatic couplers to select as the standard (from no more than three proposals), so Europe still uses the 200+years old prehistoric "buffer and hook", killing dozens of yard workers yearly on accidents related to the coupling.
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marcopete87
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Re: Fluorescent lighting on 25 cycle current « Reply #24 on: September 04, 2015, 02:13:29 PM » Author: marcopete87
Europe still uses the 200+years old prehistoric "buffer and hook", killing dozens of yard workers yearly on accidents related to the coupling.
do you mean pantograph?
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Re: Fluorescent lighting on 25 cycle current « Reply #25 on: September 04, 2015, 04:42:06 PM » Author: Roi_hartmann
Europe still uses the 200+years old prehistoric "buffer and hook", killing dozens of yard workers yearly on accidents related to the coupling.
do you mean pantograph?
I think he meant couplers: https://en.wikipedia.org/wiki/Railway_coupling
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Medved
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Re: Fluorescent lighting on 25 cycle current « Reply #26 on: September 05, 2015, 08:45:57 AM » Author: Medved
Exactly, I was talking about the things connecting the cars together. Yes, there are many automatic couplers in use in Europe mainly on the passenger units, but those are proprietary designs for the given train maker, not compatible to each other, so for e.g. towing the damaged train to free the track you have to use special converter (again to the standard "buffer and hook") to connect the hauling locomotive...
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marcopete87
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Re: Fluorescent lighting on 25 cycle current « Reply #27 on: September 12, 2015, 02:33:19 AM » Author: marcopete87
Exactly, I was talking about the things connecting the cars together. Yes, there are many automatic couplers in use in Europe mainly on the passenger units, but those are proprietary designs for the given train maker, not compatible to each other, so for e.g. towing the damaged train to free the track you have to use special converter (again to the standard "buffer and hook") to connect the hauling locomotive...

ok.


what about to return to topic?
what could be an 25Hz 3 phase system?
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