Kazuya Ikeda

Tests of Superconducting Traction Transformer for Railway Rolling Stock

We have been developing a lightweight and high-efficiency superconducting traction transformer for railway rolling stock. We designed and fabricated a prototype superconducting traction transformer of a floor-mount type for Shinkansen rolling stock. In this study, we present test results such as type test, system test and vibration test. We performed the type test in accordance with JIS, E5007. In this test, we measured the basic electrical characteristics. In the system test, we tested the transformer with a dynamic simulator for rolling stock, as a converter connected at secondary winding, and verified the operating characteristics. We performed vibration tests in accordance with JIS, E4031, vibrating the transformer on a shaking table with three-dimensional movement. As a result, we could verify that the transformer satisfied the requirement almost exactly as initially planned.

Fabrication of Superconducting Traction Transformer for Railway Rolling Stock

We designed a floor type single-phase 4 MVA superconducting traction transformer for Shinkansen rolling stock. In this study, we fabricated a prototype superconducting traction transformer based on this design. This transformer of the core-type design has a primary winding, four secondary windings and a tertiary winding. The windings are wound by Bi2223 superconducting tapes and cooled by subcooled liquid nitrogen. The core is kept at room temperature. The cryostat is made of GFRP with two holes to pass core legs through. The outer dimensions are about 1.2m × 0.7m × 1.9m excluding the compressor. Its weight is 1.71t excluding that of refrigerator and compressor. The transformer was tested according to Japanese Industrial Standards (JIS)-E5007. We confirmed that the performance of transformer has been achieved almost exactly as planned. The rated capacity is equivalent to 3.5MVA in the superconducting state.

Fabrication of inner secondary winding of high-T/sub C/ superconducting traction transformer for railway rolling stock

We studied the possible application of high-T/sub C/ superconducting traction transformer to railway rolling stock, and designed an iron core type two-leg 4 MVA superconducting traction transformer for Shinkansen. This traction transformer has a primary winding, four secondary windings and a tertiary winding. The four secondary windings are independent of each other. Two secondary windings are arranged around each leg of the iron core and placed inside and outside the primary and tertiary windings. In this study, we fabricated a high-T/sub C/ superconducting coil whose form and dimension are the same as those of the inner secondary winding. This coil can be used as the inner secondary winding of the experimental high T/sub C/ superconducting traction transformer that will be fabricated in the future. The inner secondary winding has 96 turns and a layer with eight parallel Bi2223 superconducting tapes. Transposition among the superconducting tapes is performed 15 times every six turns. We measured the voltage-current and AC loss characteristics when it was cooled in saturated and sub-cooled liquid nitrogen.

Development of superconducting transformer for railway traction

We have been developing superconducting transformer for high speed train. Its objects are reducing the weight and energy consumption. We have developed 4MVA class superconducting transformer in 2004. After that, we have improved the efficiency from 96% to 98%. We also have developed 1kW prototype lightweight refrigerator which is essential to realize superconducting transformer.

Development of a Superconducting Transformer for Rolling Stock

Having undertaken studies into a lightweight and highly efficient superconducting transformer for rolling stock, we developed a prototype with a primary winding, four secondary windings and a tertiary winding using Bi-2223 high temperature superconducting wire. Its primary voltage is 25kV, which is widely adopted as the catenary voltage on the worlds high-speed lines. We adopted liquid nitrogen cooling, the weight being 1.71t excluding the refrigerator. The maximum output available to maintain superconductivity is 3.5MVA. We also introduce railways in Japan.