Light Rail Vehicle

Overview

A light rail vehicle is an electric multiple-unit street and segregated-track tram sized between a city tram and a metro car. This is a bidirectional, three-section articulated design: two end modules each carry a driving cab, and a short low-floor center module is suspended between them over a non-powered bogie. Articulation lets the long carbody negotiate tight street curves, while the partial low floor gives step-free boarding from low platforms. Power is drawn from an overhead catenary at 750 V DC through a roof pantograph and returned through the running rails. Such vehicles run on segregated alignments, in mixed street traffic, and through pedestrian zones, accelerating and braking frequently, so regenerative braking and a compact running gear matter as much as top speed.

How it works

The vehicle rests on three bogies. Each Railway Bogie is a welded frame carrying two Wheelset units on Axlebox Bearing axleboxes, with Coil Spring primary suspension between axlebox and frame and air-spring secondary suspension between frame and carbody. The two end bogies are powered: each drives two Traction Motor units, three-phase asynchronous machines, through an Traction Gearbox reduction on the axle. The Center Trailer Bogie under the center module is an unpowered trailer.

Electrically, the Pantograph collects current from the catenary and feeds the High-Voltage Line, whose vacuum main breaker and surge arrester protect the roof equipment. Two Traction Inverter units convert the DC line into variable-voltage, variable-frequency three-phase output for the motors, and during braking they feed energy back to the line. Mechanical Friction Brake Unit units on each axle supplement the electrodynamic brake and hold the vehicle at rest.

Passengers board through six Plug Door plug doors, each driven by a motorised operator. The saloon is climate-controlled by roof HVAC Roof Unit units and lit and seated as a fit-out. Each Driver Cab carries a master-controller desk and driver displays. The Train Control & Management network links traction, brakes, doors and HVAC and reports faults to the driver, while the Auxiliary Power Converter derives the low-voltage and battery supplies that keep control and lighting alive.