A new generation of very high speed trains AGV (Automotrice Grande Vitesse)

A new generation of very high speed trains AGV (Automotrice Grande Vitesse)

19 Sep 2008

First dynamic tests

In 2003 Alstom decided to anticipate market needs with the launch of a fourth-generation very high-speed train. The new train was designed to meet a specific challenge. It was to provide higher performance levels and reliability along with controlled costs and thus offer operators a concrete advantage in terms of safety, comfort, environmental protection and controlled running costs.

Alstom has drawn on over thirty years experience in very high-speed applications to design and develop the train, opting for a radically new approach in the railway industry by financing the AGV (Automotrice Grande Vitesse) entirely from its own resources, without fixed customer specifications. It quickly proved essential to produce a prototype for use in ’actual size’ checks of the simulations and computer modelling produced by engineering departments and design offices.

The prototype AGV was unveiled on 5th February 2008 at the Alstom Transport plant in La Rochelle (France), and has undergone its first dynamic tests in the Czech Republic on the speed track at the Velim Rail Test Centre. The test runs started at speeds of up to 40 km/h working towards the maximum permitted line speed at Velim of 200 km/h. This testing programme will finalise the development phase and validate Alstom’s new very high-speed platform in the run-up to final approval.

Although these tests are being performed at a lower speed than the AGV’s design speed (360 km/h in commercial operation), they nevertheless provide a very accurate picture of the dynamic behaviour of both the train and most of its components.

Real laboratory on wheels

No fewer than fifteen engineers from various Alstom Transport manufacturing sites will perform tests on the AGV prototype to September 2008. The AGV will travel nearly 60,000 km fitted with over two thousand sensors during the months of tests. The measurements and data compiled will be transmitted and analysed by the Alstom engineering departments, who will suggest the necessary adjustments and modifications for the train to be validated.

The 7-car prototype serves as a real laboratory on wheels, and is now configured entirely for the needs of the dynamic test campaign being carried out at Velim. Only two cars are fitted with seats, with the five other cars entirely fitted out for test purposes. The first two provide a workstation for the engineers, the third houses the generator supplying electricity to the measuring instruments, the fourth acts as a spare parts store for the train and the fifth is the living area.

Wheel-rail dynamics

All the components used in this first AGV have been designed and developed at the company’s various Centres of Excellence in France. Tarbes for the traction drive, Le Creusot for the bogies, Villeurbanne for the control electronics, Ornans for the traction motors and La Rochelle for the body structure and the trainset layout. This was also the logic behind the first crash tests in Reischoffen and the first climatic chamber measurements in La Rochelle.

The test programme was launched in La Rochelle with a series of static and low-speed measurements and validations after assembly and production of the trainset. Only the main functions, like the traction drive steering, the pantograph raising and lowering controls, and the door opening and closing, were checked under two voltages (25 kV and 3000 V). A few additional checks, such as managing the main circuit breaker and commissioning batteries and auxiliary voltage selectors, were also made when the train first began running, at up to 40 km/h.

The measurements carried out by the engineers will focus on the wheel-rail dynamics, i.e. the quality of the contact between these two elements. It would have been extremely difficult to model wheel-rail dynamics using computers. These tests involve checking the vibration level perceived by the passengers by placing sensors on the bogies and inside the trainset. For the AGV, the first very high-speed train entirely made up of articulated cars, this also involves checking the dynamic behaviour of the trainset.

Pantograph-catenary interaction

The engineers will also be examining the pantograph-catenary pairing. Installed at the first passageway between cars, the pantograph is particularly vulnerable to disturbance caused by the train nose. Roof-mounted cameras will record the effect of the pantograph on the catenary at various speeds and its ability to collect the current. In particular, the number and duration of electric arcs will provide engineers with information on the adjustments to be made. The pressure of the pantograph on the catenary can be adjusted continuously with a fully automated system.

The AGV’s innovative new synchronous permanent magnetic motors carry the latest developments in power electronics, allowing them to operate under the four types of electric voltage found in Europe: 1500, 3000, 15000 volts and, more widely used in the rest of the world, 25000 volts. Very precise development is necessary for these motors and the traction drive motor to operate under these voltages. Their operation is monitored to control wheelslip during start up and locking of wheels when braking. Electronic systems regulate the braking as they do in modern automobiles.

Regenerative braking

All the train’s functional elements are validated dynamically at Velim, following the same programme as the static tests in La Rochelle. This involves testing over a hundred functions controlled from the driver’s cab with the train operating normally and in degraded mode - controlling pantographs, voltage selections, inside and outside lighting, air-conditioning and circuit breaker closure. These tests will also be used to check the procedure for feeding information back to the driver should an item of train equipment malfunction.

The AGV braking system is one of its most complex elements. It is therefore tested under extreme conditions, in emergency situations, in normal and degraded mode, under normal and reduced adhesion conditions. This is all done at a variety of speeds between 30 km/h and 200 km/h. One test causes the train to brake on a section of rail made slippery with soapy water, simulating phenomena such as the presence of leaves on the track. Measuring the train’s stopping distances will identify necessary adjustments. One reason for the complexity of the AGV braking system is the fact that it combines a rheostatic brake with a regenerative brake. Any power generated by the motors during braking not consumed by the train can be sent to the national grid. This system, which requires numerous adjustments, will also be validated at Velim.

Acoustic tests

AGV is a means of transport in line with sustainable development requirements, producing very low greenhouse gas emissions. It emits a mere 2.2 g/km /passenger, i.e. thirteen times less than a bus (30 g), fifty times less than an automobile (115 g) and seventy times less than an aeroplane (153 g). Although the aerodynamic drag, one of the train components with the highest consumption, can be simulated fairly accurately in a wind tunnel, it is important nevertheless to check its conformity under actual conditions. The Alstom engineers will check the aerodynamic coefficient (Cx) of the AGV.

Reduced sound nuisance was another environmental aspect the Alstom engineers focused on during design. The acoustic tests at Velim will involve arranging microphones, in accordance with the standards in force, the length of the test track, to measure the noise emitted as the train passes. Reducing aerodynamic and train movement noise has also been studied meticulously with the aim of ensuring the comfort of passengers and drivers alike. Microphones installed at different heights in the cab, the cars and the passageways between cars can simulate seated or standing passenger noise perception.

Firm order for 25 trainsets

Following the dynamic test campaign at Velim, the AGV will embark on new test sessions in France taking it to its maximum commercial speed of 360 km/h. During 2009 it will also travel on the Italian rail network as part of the approval process for delivering trainsets ordered by NTV. The new Italian Transport Company has placed a firm order for 25 trainsets (with ten on option), together with a thirty-year maintenance contract. Delivery of the first production trains will commence in 2010.

Copyright Terry Whitley.

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