Modern Tbus undergoing tests

Trolleybus design patented in 1889

Hub motor/ brake assembly for a Trolleybus

HOW IT WORKS:
THE ELECTRIC TROLLEYBUS

The Tbus works by drawing its power from overhead cables, rather like an electric tram. The difference is that, whereas the tram usually gets its power from only one large cable, with the current escaping through the rails and into the earth, a Tbus uses two, smaller, wires, drawing the current from one and returning it via the other.

When Trolleybuses were first invented back in Victorian times, the power collector took the form of a small 'trolley' which ran on wheels on top of the electric wires - hence the name: 'Trolleybus'. This was soon replaced by two sprung poles which had small wheels that ran underneath the wires instead.

These days, even the small wheels have been replaced by solid graphite contacts at the end of the poles. Despite the fact that the term 'Trolleybus' is a hundred years out of date, the name has stuck! However, people nowadays are using more up-to-date names for these incredible vehicles. In Germany, they use the term 'Obus' (because of the Overhead wires). In Britain, the terms 'Tbus', 'Trolleycoach' and 'Electroliner' have been coined.

Because Tbuses use electricity which is centrally-generated at the power station, they can use fuel more efficiently than, say, a diesel bus. This means that, even if fossil fuels are used to generate the electricity, the Tbus is still much more environmentally-friendly than any internal-combustion vehicle.

On the street, of course, the Tbus gives off no emissions at all - the electric motor is completely clean and very quiet. Typically, a modern Tbus will use a 750 volt DC system, which is converted to AC onboard for greater efficiency. Some modern Tbuses use a series of hub motors to increase efficiency further and to enable an even, low floor throughout the vehicle.

Tbuses are also capable of 'regenerative braking' which means that the braking system is designed to be used as a mini-generator to recapture some of the energy that might otherwise be lost when slowing down. Up to 40 percent of the electricity can be reclaimed in this way.

For more information about the technology behind the Tbus, please visit the Electric Tbus Group website at: http://www.tbus.org.uk/overhead.htm


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