Tokyo Metro Tested Synchronous Reluctance Traction Motors

Tokyo Metro is collaborating on the testing of a newly developed Mitsubishi Electric's propulsion system using synchronous reluctance traction motors. In 2022 the companies were evaluating this technology on the Hibiya metro line during night test runs.

Two Class 13000 cars were equipped with the technology and the objective of this development is energy and material savings. The new traction drive using synchronous reluctance motors (SynRM) promises to reduce energy consumption by up to 18 % compared to asynchronous traction motors. In addition, another benefit is that the reluctance motors do not require rare materials, in this case neodymium, compared to the permanent magnet synchronous motors used quite frequently in the rail transport worldwide.

The traction drive using SynRM has been developed by Mitsubishi Electric and also includes a new SiC traction converter, the system as a whole being branded SynTRACS. It is claimed to be the first and most powerful solution using SynRM technology for rail deployments where high performance has not been easy to achieve. Two cars (front and an adjacent second car) are fitted with reluctance motors, each rated at 250 kW (maximum 450 kW) and weighing 562 kg. They are fed by a traction inverter mounted under the intermediate car.

Such traction motors are also expected to have a 10 % improvement in service intervals and a 7.7 % improvement in recuperation brake efficiency. The disadvantage of reluctance rotors in general is that they are less smooth running and have a more pronounced sound, especially at lower speeds, due to torque fluctuations. However, this is not expected to affect the passengers in the car.

Testing verified the promising performance of SynTRACS technology and its potential for regular use. Class 13000 Tokyo Metro units have a 1,067 mm track gauge, a 2,780 mm width and a height 3,995 mm above the TOR. Their maximum service speed is 110 km/h.