Train busbar
The train busbar (ZS) is a cable that connects all the carriages of a train with each other and with the locomotive in order to supply all units with electrical energy from a central point. Here, busbar denotes an electrotechnical device. The tracks form the return conductor of the single-pole train busbar .
history
Passenger coaches were originally heated with stoves built into each coach. Later, a steam heating line (pipeline) was laid through the train in order to supply the cars with steam from the locomotive boiler or a special heating car . With the introduction of electrical operation, they wanted to heat the cars electrically and laid an electrical line through the train for this purpose. This was referred to as a heating cable following its intended purpose . Since the electrified routes were isolated isolated operations for a long time and the cars were supposed to be used freely, they were equipped with electric and steam heating, beginning in the 1920s. For the same reason, the passenger coaches received axle generators to supply the lighting and comparable small consumers. The stand was powered by accumulators, which were charged by the axle generators while driving. With the progressive change in traction, the international UIC and OSJD railway associations stipulated in the 1970s that the train heating system should only be operated electrically to avoid double equipment. With the advent of air conditioning systems and other electrical consumers in trains, whose required power could not be generated by the axle generators, the name was changed to train busbar. The heating cable, which is always coupled in this context and kept under voltage during operation, could also be used with comparatively little effort to supply the other electrical consumers in the passenger coaches. This meant that the axle generators and the associated switching devices could be omitted. Due to the fact that the train bus can also supply power while the vehicle is stationary, it was possible to roughly halve the battery capacity in the passenger coaches. In addition, there was no maintenance of the generator systems, and the running resistance was also reduced. The fact that energy is no longer converted from electrical to mechanical energy and back has also improved the efficiency. In the case of technical data on locomotives , besides the traction power, the heating power is often given, which means the maximum power on the train busbar.
Types of power supply
Supply from the catenary
In the case of railways with direct current supply, the electricity for the train power supply is taken directly from the overhead line and fed into the train busbar. Accordingly, the voltage in the train busbar varies from 600 to 3000 volts . The DC voltages of 1.5 kV and 3 kV are standardized for the European standard gauge network.
Supply from transformer
On traction vehicles that are supplied with alternating current , the transformer generally has a so-called heating winding from which the train busbar is supplied with alternating current. A heating voltage of 1000 V has been used in the railways electrified with 15 kV, 16.7 Hz since the 1920s. Since the electrification with 25 kV, 50 Hz came from France, the voltage level of 1.5 kV with 50 Hz became another standard. France was the first country to use contact wire voltages of 1.5 kV and 25 kV 50 Hz. This means that the wagons can be used in both sub-networks without any technical changes. For the same reason, there is another, internationally not standardized alternating heating voltage of 3 kV with 50 Hz in the former Czechoslovakia. On the meter-gauge network of the Rhaetian Railway and Matterhorn-Gotthard Railway , electrified with 11 kV at 16.7 Hz, a heating voltage of 300 V 16.7 Hz used. The high currents caused by the low voltage sometimes require a second transformer in the train in order to be able to feed the train busbar divided into two segments. This avoids overloading the train busbar.
Supply from the generator
Earlier diesel locomotives were not equipped to supply the train with energy or they had a boiler to supply the steam heating line. A car with a diesel engine and a flange-mounted generator was then used to power the train ( generator car ). In some cases, such a system was also installed in diesel locomotives. With the greater engine output and the development of power electronics, the generator could then be flange-mounted directly to the main diesel engine. The current is then brought to the required voltage and frequency with an electronic converter. The converter is necessary because the speed of the diesel engine fluctuates during operation.
In Germany, the standard requires 940 V to 1060 V and 16.7 Hz. The first to be used were envelope converters in which the higher-frequency phases of a 6-pole generator were switched on using thyristors until the half-wave was long enough. It was then switched to the other half-wave and the process was repeated. As long as the electricity was only used for heating purposes, that was sufficient. However, battery chargers and air conditioning systems generate an inductive electrical load on the train busbar, which causes converters of this type to fail; the thyristors no longer go out at the end of the half-wave. The thyristor with opposite polarity is ignited and a generator short circuit occurs. For this reason, diesel locomotives are prohibited from operating appropriately equipped wagons.
The next generation of converters works with a direct current intermediate circuit and builds the half-wave as a square half-wave with a switch-on and a quenching thyristor or uses GTO thyristors . These generators can withstand inductive loads, but the non-sinusoidal half-wave leads to strong harmonic waves. Since there are still safety systems with 50 Hz track circuits in the non-electrified network in Germany and 50 Hz is a harmonic of 16.7 Hz, the EBA demands that the converter frequency be changed to 22 Hz in order to rule out any interference.
Equipment of passenger coaches
Electrical consumers such as light bulbs in passenger coaches were supplied with electricity via axle generators and, when stationary, by the accumulators ("batteries") charged during the journey ; 24 or 36 V DC voltage were common, for example 48 and 110 V later in Germany. The electrical resistance heating or the steam heating also worked independently. The train busbar, then known as the heating line, was only coupled in winter, like the steam heating line. To adapt to the different supply voltages, the individual radiators were connected in groups in series and in parallel. In some countries, for example in Germany, the heating voltage could be switched to electric locomotives. A voltage of 800 V was tapped via an additional tap on the main transformer for the transition period with a lower heating output required. Initially there was a third voltage of 600 V, but this had not been used since the 1930s and was no longer provided for in new locomotives. The tap for the reduced heating voltage of 800 V was installed in the DR locomotives for the last time in the 211 and 242 series , but was no longer used a little later. It was comparable with the other railway administrations that use the 15 kV system.
With the increase in electrical consumers, a supply had to be set up from the train busbar. A charger now supplies the accumulators with power, in return the axle generators could be dispensed with. In order to be able to use loads of the usual voltage levels of 400 V three-phase current or 230 V single-phase alternating current, an inverter is connected after the accumulator or the charger . For example, the lighting can remain switched on during a locomotive change. A power control switches off certain consumers, in particular the air conditioning system, when the train busbar is de-energized. This prevents the batteries from being discharged too quickly.
Coupling of the train busbar
So that wagons from different manufacturers are also internationally compatible with one another, the UIC has standardized the train busbar in the UIC 552 standard. Depending on the operating conditions, it carries an alternating voltage of 1000 V with 16.7 Hz, or 1500 V with 50 Hz or direct voltages of 1500 V or 3000 V, in addition, square-wave or trapezoidal alternating voltages are possible when operated with diesel locomotives, as explained above. At the Deutsche Reichsbahn in the GDR , an alternating voltage of 1000 V at 22 Hz was fed in via the train bus for diesel locomotives because of the possible influence on the track circuits fed with 50 Hz. Most modern on-board converters also work with 1000 V 50 Hz, so that electricity can also be drawn from local networks through stationary feed-in. Particularly in the case of push-pull trains traveling across borders between the 15 and 25 kV networks, there is no need to switch the voltage when the supply frequency is changed. The power supplies of modern passenger coaches can usually cope with the non-standardized combinations of 1000 V with 50 Hz and 1500 V with 16.7 Hz, and for many vehicles, especially from the Czech Republic, Slovakia and Austria, the additional frequencies are also specified in the heating grid.
In addition to the single-pole train busbar for the energy supply , the wagons are usually also connected with an 18- or 13-pole UIC cable for door locking, lighting control and data exchange (e.g. for train destination displays , announcements, etc.).
A single electrical coupling may be loaded with a maximum of 600 A. However, the lines built into the car now usually allow a load of 800 A to 1000 A. Since a single modern car can easily draw more than 50 kVA of power, on the instructions of the railways, both couplings are used between the cars on some long trains in order to avoid overloading them.
On branch and small railways with direct current operation, roof rods were often used instead of cable connectors. If there are plug connections, these often do not correspond to the UIC standard in terms of dimensions or they are counter-rotating or coupled at the edge of the roof.
See also
swell
- Horst J. Obermayer: Paperback German Diesel Locomotives. Franckh'sche Verlagshandlung, Stuttgart 1986, ISBN 3-440-03932-3
- Hans Schneeberger: The electric and diesel traction vehicles of the SBB, Volume 1: years of construction 1904–1955. Minirex, Luzern 1995, ISBN 3-907014-07-3