For the purpose of reducing noise and maintenance, the Railway Technical Research Institute (RTRI) has developed torally-enclosed transaction motors in place of the self-ventilated motors currently in widespread use as traction motors for motor car trains on conventional lines (Fig. 1).
      Since torally-enclosed transaction motors have no air intake, it is not necessary to clean filters or the inside of motors, achieving maintenance labor-savings. Although lower noise can also be expected due to the blocking effect, it is necessary to solve the problem of temperature rise.
      Accordingly, a synchronous motor system applying permanent magnets for the rotor was adopted, aimed at reducing heat generation and power consumption while improving efficiency (97% achieved, compared with 92% of induction motors). The temperature rise of each part of the rated points was also controlled to within limits by way of a cooling structure mechanism (Fig. 2). In comparison with self-ventilated motors, noise was reduced by about 10 dB (Fig. 3) with the same dimensions and weight.
      The next step is to put this system to commercial use as a traction motor with reduced noise and maintenance.