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AGV tailors capacity and performance to the market

31 Aug 2007

Nearing completion at Alstom's factory in La Rochelle are the seven cars of the prototype Automotice à Grande Vitesse. Alstom's Technical Director François Lacôte briefed Murray Hughes on the train's design and target market

ALSTOM'S high speed demonstration train with distributed power will soon be ready to leave its birthplace. By the end of the year the seven-car set will be fully assembled in La Rochelle ready for low-speed testing before the train travels to the Velim test circuit in the Czech Republic.

Known as Pégase, the prototype AGV heralds another generation of high speed train that combines distributed traction with well-established TGV design principles such as articulation. 'We absolutely wanted to continue developing our range of high speed trains - this is a new range, not just for one customer, but for the whole market', says François Lacôte, Senior Vice-President, Technical, at Alstom Transport.

The prototype will serve as a demonstrator for what is destined to become a family of trains with different configurations. 'From the outset the AGV was aimed at all Europe's high speed networks as a high-performance train for 300 to 360 km/h. We are well aware that this is a very ambitious target - but the design is deliberately flexible to offer different capacity and different speed maxima for different customers.'

Series-built AGVs could be configured in formations of seven to 14 cars (Fig 1), with the possibility of three short sets operating in multiple. Groups of three cars form autonomous electrical units with the transformer, converter and auxiliary equipment spread over the three vehicles; 'key cars' without traction equipment provide the flexibility for formations of seven, eight, 10, 11 or 14 cars. In terms of capacity, a 200 m long 11-car train mounted on 12 bogies would provide from 446 to 510 seats, depending upon the chosen seating density.

Lacôte describes the AGV as 'a modern response to the customer'. He explains that, despite strong interest in Alstom's double-deck TGV, customers prefer a single-deck trainset because a double-decker 'does not fit in with their own ideas for technical, cultural or other reasons'. Presentations about the TGV Duplex to customers in Italy, Germany, South Korea and China consistently generated the response that 'the double-decker is very good, but we prefer a single-deck train'. In every case, says Lacôte, 'some kind of obstacle' pushed the customer towards a single-decker.

Given the massive demand for inter-city rail travel in China, and to a lesser extent in South Korea, their railways' preference for a single-deck train is 'quite surprising'. It is no small irony to Lacôte that SNCF - whose traffic levels are significantly lower - wishes to purchase only double-deck TGVs; SNCF ordered 80 more Duplex trainsets on June 27, some of which are intended for international services (RG 8.07 p471).

Development cost

With Alstom's main domestic customer 'not interested' in a single-deck high speed trainset, the AGV is set to become the company's standard high speed product for the export market. As 'no customers were prepared to invest in developing their own high speed trains', Alstom decided to build a demonstration set at its own expense - the first time a complete high speed train has been built speculatively by the private sector.

In round figures, the price tag for the AGV programme is €100m, which Lacôte says covers 'all the development work, construction of the prototype and the initial phase of tests'. A tiny fraction of the total has been paid by subcontractors, but in other cases Alstom paid the development costs incurred by some of its suppliers.

Alstom began experimenting with distributed power in 2001 when two AGV research vehicles were married with five TGV cars to form the Elisa test train (RG 11.01 p751). Trials were sufficiently encouraging for the company to decide three years later to proceed with construction of a complete trainset, and the first bodyshell components for Pégase were laid down in 2006. By the end of July this year all seven cars were well advanced with most components installed, including the traction equipment and the drivers' desks.

Returning from a visit to La Rochelle on July 25, Lacôte was confident that 'we shall meet our target date for roll-out at the end of the year'.

Test programme

For the first three months of 2008 Pégase will undergo static tests and low-speed trials on the test track at the La Rochelle factory. At the end of March the prototype is scheduled to undertake its first trip outside France, with no less than six months of tests envisaged on the test loop at Velim in the Czech Republic. There the AGV will be able to attain 200 km/h, and there is some prospect of the trials being used for European certification tests. Despite this, Lacôte considers that six months is more than generous for the test programme.

As TGV Design Engineer at SNCF, Lacôte led the team that achieved the May 1990 world record speed of 515·3 km/h on a section of LGV Atlantique. He points to the use of the AGV traction package and bogies in the V150 programme earlier this year as a particularly demanding test for the equipment. The programme culminated in the specially-configured V150 trainset beating the previous record by 59·5 km/h on a section of LGV Est-Européenne on April 3 2007 (RG 5.07 p267).

The AGV bogies fabricated in Le Creusot had never been tested at high speed before, and Lacôte was 'completely stunned - I did not think we could do so well. If the rest of the tests go like that, we'll have no problems'. The V150 programme means that the AGV bogies and traction equipment on Pégase are effectively pre-production equipment, but all components will still be subject to extensive checks and assessment. Lacôte is careful to temper his enthusiasm with caution, stressing that 'we shall have to be completely systematic as we do not know what we will find'.

A major worry for the V150 test team had been the prospect of a failure in a mechanical or electrical component as a result of overheating. The AGV traction motors had been designed for an output of 720 kW, but during the V150 trials each motor was producing 1 000 kW. No less than 40 runs were made at speeds above 450 km/h, and six of these exceeded 550 km/h - yet temperatures remained within the permitted tolerances. Lacôte concedes that 'perhaps we were too cautious and maybe some equipment was over-dimensioned, but I prefer surprises like that rather than the other way round'.

SNCF doubtless shares that view, and Lacôte emphasises how grateful he is to SNCF 'for allowing us to put AGV equipment in the V150 trainset - it was a huge vote of confidence.'

Current collection

A critical element in the V150 programme was the pantograph-catenary interface which determined the quality of current collection. Lacôte describes the Faiveley CX25 pantograph mounted on the V150 set as 'a little gem', and the same design will equip the AGV, although without some of the V150's special features such as a single lightweight contact strip of 'metallised carbon' able to handle currents of 800 A.

During the world record run, an array of sensors allowed the arcing to be measured and adjustments made to the pantograph practically in real time from the on-board control room - in marked contrast to the 1990 exploits when Lacôte recollects stopping the test train to make adjustments to the pantograph from the roof after a run at 482 km/h had nearly torn down the catenary.

Traction equipment

The 'base design' AGV is a four-system TSI-compliant train able to accept traction power at 25 kV 50 Hz, 15 kV 16·7 Hz, 3 kV DC and 1·5 kV DC, although the 360 km/h maximum speed will only be possible with 25 kV. One issue in the early design stage was the ability to incorporate a transformer able to handle 16·7 Hz at 15 kV for operation in Germany and Switzerland, but Lacôte says that 320 km/h will be possible when drawing power at 15 kV. A speed of 250 km/h will be achievable under 3 kV DC catenary, reducing to 200 km/h at 1·5 kV.

Pégase will take power at 25 kV, 1·5 kV and 3 kV DC, and it will incorporate equipment for ETCS Level 2, together with all national signalling and train protection systems to allow it run 'from Amsterdam to Napoli'.

The AGV's underfloor-mounted traction package includes a transformer with an innovative arrangement of windings to reduce the weight. IGBT transistors in the power converter feed three-phase current to the synchronous permanent magnet traction motors, with the intermediate bus in the main traction circuit rated at 3 kV DC compared with 1·5 kV DC on the TGV POS; this allows the use of smaller and lighter cables.

In contrast to the body-slung motors on a TGV which require a tripod transmission, the AGV's traction motors are mounted in the bogies. This permits a simpler transmission and eliminates a potential source of noise and vibration from the car body - on Pégase four of the eight bogies will be powered, and the same proportion is envisaged for a production train.

Lacôte considers that the permanent magnet motor 'has great potential', asserting that it would not be difficult to develop a motor rated at 800 kW rather than the 720 kW version selected for the AGV.

Bogies and brakes tested

The AGV power bogies are 'identical and different' to those on a TGV. The long wheelbase of 3 000 mm is retained to ensure stability at critical speed, but the bogie frame is constructed from high-tensile steel, giving a significant weight reduction.

During the V150 programme comparisons were made between the AGV motor bogies and those fitted to the POS power cars, and Lacôte says that the AGV bogies offered superior performance with greater stability. The AGV's trailer bogies are 'more conventional', and wheelsets and axles are similar to those on the TGV Duplex.

It has blended rheostatic and regenerative braking, as on the TGV POS; earlier builds of TGV did not have a regenerative facility.

On the AGV the dynamic brakes are complemented by three brake discs on each trailing axle. These are intended for use only during the last stage of braking.

Four discs to the AGV design were fitted on each axle of the trailer bogies of the V150 trainset, and on one occasion at the end of March emergency braking was applied when the train was travelling at nearly 507 km/h - a real-life test for the brakes which caused grave concern to the engineering team on board. 'We really thought we were on the limit - each disc had to absorb 36 MJ of energy', explained Lacôte. Back in the Technicentre Est-Européen where V150 was based, the engineers inspected the discs which, despite having reached a temperature of 650°C, proved to be in 'impeccable' condition, serving to confirm 'the enormous progress we have made in material design'.

For comparison, a disc on a TGV Sud-Est trainset dating from the late 1970s was designed to handle 13 MJ and that on a TGV Atlantique set from the mid-1980s 18 MJ. Had TGV Atlantique discs been subject to the same emergency application, conjectures Lacôte, the entire set of discs would have had to be replaced. The AGV's brake discs are designed for 24 MJ with 'very special' pads manufactured from materials able to guarantee a constant coefficient of friction, even in damp conditions.

Alstom gave serious consideration to fitting the AGV with eddy-current brakes which are 'very interesting'. However, Lacôte feels they are 'heavy and expensive'. Ensuring that they do not introduce a safety risk makes them 'too complicated', he says, insisting that he does not want them on the AGV. Nonetheless, provision has been made for two eddy-current brakes to be installed on Pégase.

Composite components

At 17·3 m, the car body length of the AGV's intermediate cars is slightly shorter than the 18·7 m on a TGV, and this will allow a slightly wider body than the German ICE3.

The bodyshells of all seven cars are fabricated from aluminium, but the train will incorporate two structural articulation sections that feature novel technology in the form of carbon composite material. The AGV articulation will be slightly wider than on a TGV to permit more space in the inter-car gangway, and the opportunity is being taken to experiment with a material that saves 700 kg per articulation.

Lacôte says that the composite articulation structure has been put through fatigue tests at Vitry and that it has also undergone tests at Reichshoffen to check its performance in a collision.

In-house styling

Alstom - and Alstom Transport President Philippe Mellier in particular - is anxious to keep the design of the front end of Pégase under wraps until it emerges from La Rochelle - perhaps reflecting Mellier's background in the automotive industry. In 2005 the company appointed Xavier Allard as its in-house stylist, and the AGV may become the product on which Allard's future reputation will rest.

Table I. Principal data for AGV prototype trainset

Gauge mm 1 435
Overall length m c125
End car length mm 17 100
Intermediate car length mm 17 300
Bogie wheelbase mm 3 000
Width mm 2 900
Maximum speed km/h 360
Weight tonnes 272
Continuous power rating kW 5 760

AGV design features

Distributed power
Flexible formation and capacity
Multi-voltage (three systems on prototype)
Design speed up to 360 km/h
New materials used for brake discs and pads
Some structural elements of composite material on prototype

Italian response awaited

ON MARCH 25 Alstom submitted its first bid for its AGV design to Italian private open access operator Nuevo Trasporto Viaggiatori. The proposal was for 25 trainsets, each of 11 cars, with an option for 10 more sets. A response was promised by the end of June, but a month later Alstom was still waiting to hear.

Negotiations were continuing at the end of July, but little progress was expected during August as both the French and Italian business communities had geared down for the summer holiday.

In Italy, the NTV consortium is considered to be of good standing, but there are fears that politicians may jib at allowing a private-sector company to be the first to operate a new generation high speed train on a state-funded network of high speed lines. 'Were Virgin or another company to propose something similar between Paris and Lyon, I can imagine that Sarkozy or other politicians would have something to say', remarks François Lacôte.

  • CAPTION: Fig 1. The prototype seven-car AGV trainset is designed for a maximum speed of 360 km/h, but production versions will be offered with a range of different configurations in both high and low-density layouts
  • CAPTION: The AGV power bogies trialled in the V150 programme were found to offer greater stability at high speed than the bogies used on a TGV Duplex power car
  • CAPTION: One of the AGV end cars takes shape in the Alstom factory at La Rochelle

'From the outset the AGV was aimed at all Europe's high speed networks as a high-performance train for 300 to 360 km/h.'

François Lacôte
Senior Vice-President, Technical
Alstom Transport

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