Bexleyheath bus pantograph
London Buses route 132 runs between Bexleyheath Shopping Centre and North Greenwich bus station. It is operated by London Central, trading as Go-Ahead, out of their Bexleyheath (BX) garage. Since July 2022, the route has used all electric Alexander Dennis Enviro400EV vehicles. To cater for these vehicles, a pantograph charger was installed at Bexleyheath bus garage to allow rapid charging to 'top up' the battery during the day. This is known as ‘opportunity charging’ because it provides charging during the brief period while the bus is standing by at the end of the route.
The white box beside the pantograph arm, manufactured by ABB, contains the voltage conversion and control equipment. In operation yellow lines guide the driver to the correct lateral position but the design allows for up to 30 cm range of position. The driver positions the front wheels between the humps on the road surface. This gives a forward location with only a few centimetres of error. The driver presses a button in the cab which communicates by wifi to the charging station. The inverted pantograph (the red part, manufactured by Stemmann-Technik in Schüttorf, Germany) descends and makes contact with terminals on the bus. Charging commences.
An important difference between this pantograph and that used for rail vehicles is that it makes four separate contacts instead of one. This can be clearly seen in the Pantograph photo: each of the two contact rails is divided into two separate sections about 50 cm long separated by a 15 cm gap. See this (unfortunately very small) circuit diagram. The four connections are: 1) DC+ and 2) DC- delivering the actual charging current; 3) protective earth connected to earth in the charging station and to the bus netalwork at the other end and 4) a monitoring conductor. On the bus this last one is also connected to the bus metalwork but in the charging station it is connected to earth via a resistance monitoring circuit. When the pantograph is in good contact with the bus the resistance between the protective earth and monitoring conductors drops to a negligible value. The monitoring circuit detects this and connects the DC+ and DC- conductors.
External links[edit]
- TfL’s announcement of the introduction of the charger
- Evening Standard article includes picture of pantograph descending
- Ian Visits has a photo of the wifi button in the cab.
- This page has the tiny circuit pic.
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