To replace the induction motors now in use as traction motors, the RTRI has developed a high-efficiency permanent magnet synchronous motor that uses a totally-enclosed self-cooling system, thereby aiming at reduced maintenance and energy consumption, and low-noise operation. The system is intended to replace the conventional cooling units that need such maintenance work as filter cleaning and disassembling and cleaning of components.

The output of the motor is 270 kW, which is the same as the maximum output of the traction motors used for conventional-line (narrow-gauge) vehicles (whereas the output of standard commuter transport EMUs is about 200 kW, for reference). As adoption of a self-cooling system will lower the cooling capacity and compromise high-output operation, one problem to be tackled was how to suppress an increase in temperature to within the limit. However, the RTRI’s new cooling structure and optimal design (Figs. 1 and 2) enabled production of a high-output motor with energy loss reduced by half in comparison with that of the induction motor. As a result, it is expected that power consumption in running will be cut by about 10% (Fig. 3). It has also been confirmed that the noise level is reduced by 7 dB for a single motor unit (Fig. 4).

After the stationary test, a traction motor (which is a remodeled version of the developed motor) was mounted on U@Tech test car of the JR West and subjected to a running test from which the effects of improved control performance and noise reduction were confirmed.