Building upon experience with its Advanced Commuter Train prototype, East Japan Railway has decided to adopt articulation for its latest Tokyo suburban EMUs

WHEN the cherry blossom blooms in Tokyo, local residents flock to the parks and green spaces to hold hanami parties under the cherry trees. This year the blossom started to open on March 27, which happened to be a landmark day for JR East.

The day marked the final acceptance test for JR East's future commuter train, Series E331. This is a pre-production version of the experimental Advanced Commuter Train (RG 4.02 p201), which has been used to evaluate a number of design concepts.

The AC Train, as it is known, was successful enough for JR East to decide to move to a version that could be built in large numbers, and the E331 may prove to be the standard design for several Tokyo commuter routes in the future.

The E331 will be tested on the Keiyo line from Tokyo to Chiba, and an intensive programme of trials is planned between now and September. Once JR East is satisfied with performance, passengers will be given the opportunity to give their own assessment.

The train is formed of two sets of seven articulated cars, with three out of eight bogies on each set powered (Fig 1). Both stainless steel and aluminium bodies were tested on the AC Train, and the choice was made to use stainless steel for the E331. Another comparison was between bogies with two or four air springs for the secondary suspension, the decision being in favour of four springs as this offered a lower risk of derailment.

The AC Train had outside-hung sliding doors, but JR East found that these were vulnerable to the build-up of dirt, snow and ice. The operator therefore decided to revert to conventional doors sliding into bodyside pockets.

The direct-drive traction motors which eliminate gears and hence noise and transmission losses have been retained, albeit with some modifications. Fed with variable voltage and variable frequency power from an IGBT inverter module, each motor has an hourly rating of 200 kW. Maximum speed of the Series E331 is 120 km/h, which is the same as earlier JR East commuter trains.

The 200m train length corresponds to a train of 10 conventional cars, but on Series E331 the cars are about 50 mm wider. It was originally planned to provide extra passenger capacity in the wide inter-car gangways, but new regulations introduced after the fire on a metro train at Taegu in South Korea require the fitting of end doors to each vehicle.

Design life will be 20 to 25 years, confirming that JR East has broken with the concept of the half-life train embodied in Series 209. A big question for JR East will be life-cycle and maintenance costs. Maintenance will be a particularly critical issue, as none of the existing depots or workshops in Tokyo is geared up to cope with articulated cars.

Table I. Principal data for Series E331 Tokyo commuter EMU