Engineering Efficiency in Railcars
World's First Field Trials for Energy Conservation in Commercial Railcars
Eco Changes for a greener tomorrow
Measuring energy savings from SiC inverters in Ginza Line railcars
In February 2012, Mitsubishi Electric began conducting the world's first field trials to measure the energy savings delivered by an SiC* inverter installed in a commercial railcar. Working closely with Tokyo Metro Co., Ltd. on its Ginza Line, we field-tested a Series 01 railcar equipped with both an SiC inverter and a modified braking system. The result: 38.6% energy savings compared to a conventional Series 01 railcar.
*SiC is silicon carbide (a chemical compound of carbon and silicon)
How we determined the results of the field trials
In these field trials, a Series 01 railcar on Tokyo Metro's Ginza Line was equipped with a main power-circuit system consisting of an SiC inverter and a high-efficiency, totally enclosed induction motor. The power consumption and regeneration rate of the system were measured. Compared to the existing main power-circuit system of a conventional Series 01 railcar, the following results were achieved (the values are the average of readings recorded between July 30 and August 17, 2012).
Savings of 38.6% in main power-circuit system energy consumption
Compared to a conventional system, a 38.6% overall reduction in energy consumption was achieved as a combined result of decreased power usage during travel and an increase in regenerated power (as a result of the change to a regenerative braking system).
Return of 51% in power regeneration ratio
The power regeneration ratio is the power that is returned to the overhead wires using regenerative braking versus the total power used to run the train. In our tests, it improved to 51% versus 22.7% for the conventional system
Specifications: SiC inverter for railcars
|Input voltage||600V/750V DC|
|Main power-circuit system||Two-level voltage-fed PWM inverter (with regenerative braking)|
|Motor control system||135kW motor x 2 units x 2 groups|
|Cooling system||Natural air-cooling system|
Coming soon: new methods of railroad system energy conservation
Mitsubishi Electric has been addressing total energy management and conservation for railway systems in four areas: railcars, stations, terminals and railways. Our recent Ginza Line field trials were an important part of developing energy-saving measures in railcars. Moreover, the tests also served to achieve even more effective utilization of regenerative energy in combination with the auxiliary power supply unit for stations, which is currently being field tested at Tokyo Metro's Nishi-Funabashi Station. In the future we will be working to develop even more energy saving systems for railways.