Polyamp AB - Train Low Voltage Supply

Polyamp AB has supplied switch mode DC/DC converters to the train industry and operators since 1973. The applications in train low voltage supply include auxiliary voltage for the GTO drive line, low voltage distribution such as battery chargers, 13.6V, 24V or 48V distribution, comfort voltage for passengers and equipment supply. Polyamp's equipment supply covers:

• Radio and telecom for driver and passengers
• Control and Safety systems
• Lights - head lights
• Signs - Internal or external
• Wipe washers - DC motors
• Air conditioning
• Microwave ovens etc.
• Comfort equipment for passengers such as seat video and audio, video screens etc.

The difference between distribution supply and equipment supply is that distribution supplies several equipments. Technically the output must have the same EMC performance as the input (ENV50121-3-2). Polyamp provides DC/DC converters (insulated) from 40 to 1000W, switch regulators (un-insulated) from 500 to 6kW, battery chargers 24V 200A to 110V 50A, battery charging computers and special DC/AC inverters.

POLYAMP CLIENTS INCLUDE

• Toronto underground, Rolls Royce/Bombardier, Canada
• Dockland line, Brush Traction, UK
• Swedish Rail SJ, Sweden
• Bangkok BTS, Siemens SGP Austria
• Stockholm underground SL, Motorola, Sweden
• Chinese Railways, ECS Austria
• X2000 and V2000 for SJ and SL, ADtranz, Sweden
• Head light supply, ADtranz, Sweden
• Norwegian Rail NSB, Ascom and SMS Telecom (Switzerland, Sweden)
• Bangkok BTS, Siemens SGP Austria
• Austrian Rail ÖSB
• Hong Kong Airport Link, Brush Traction, UK
• Singapore MRT, Siemens SGP, Austria

Comfort voltages for passengers are planned on many lines. The question is which power supply strategy to use?

AC distribution by centralised inverters the advantages include the fact that most passengers have AC adapters. This method can also be used for cleaning equipment. Standard AC plugs and equipment can be used giving low installation costs. The disadvantages are that Inverters are relatively more expensive and there can be problems with interference on the AC side.

AC supply by local inverters offers the advantage of no interference but the Inverters are relatively expensive and, due to problems with load characteristics, some equipment might not work.

DC distribution by centralised DC/DC converters is the lowest cost strategy but DC-adaptors are not usually filtered which creates interference. More expensive installation as local filters have to be introduced. 13.6V cannot be distributed without large distribution cables to avoid voltage drop. In this instance, one should establish whether passengers have DC-adaptors.

DC supply by local DC/DC converters also offers the advantage of no interference but the supply has to be integrated in the seat or luggage shelf. One should establish whether passengers have DC-adaptors.