Hiroshi Hata

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.

Fabrication of winding model of high-T/sub c/ superconducting transformer for railway rolling stock

We fabricated two high-T/sub c/ superconducting coils that simulated the winding of a traction transformer for railway rolling stock. The multi-layer solenoid coil to simulate the primary winding of the transformer had five layers with a single Bi2223 superconducting tape. The closed solenoid coil to simulate the secondary winding of the transformer had one layer with eight parallel Bi2223 superconducting tapes. We measured the voltage-current, AC loss and current sharing characteristics of these coils cooled in saturated liquid nitrogen at 77 K. As a result, we concluded that the multi-layer solenoid coil is applicable to the primary winding and the closed solenoid coil is also applicable to the secondary winding.

Feasibility study of oxide superconducting transformers for Shinkansen rolling stock

A feasibility study of an oxide superconducting transformer for Shinkansen rolling stock was made from the viewpoint of light weight. On the basis of the observed critical current and AC loss properties for the currently developed Bi2223 silver-sheathed superconducting wires, which both have large anisotropy, superconducting transformers cooled by subcooled liquid nitrogen with the same specifications as the conventional ones were designed. The total weight of the transformer system including a cryocooler was quantitatively evaluated. As compared with the weight of conventional ones, the optimum winding configuration and 1-turn voltage were searched for. As a result, the following suggestion was obtained. For the sake of light weight, the transformer should be core type with closely wound cylindrical windings so as to reduce the perpendicular magnetic field to the wide surface of superconducting thin wires and the AC loss in a superconducting wire needs to be much reduced as compared with the currently developed one. Finally, according to the obtained optimum parameters, the conceptual design of a single-phase 4 MVA-25 kV superconducting transformer for Shinkansen rolling stock was performed whereby the drastic reduction of weight was shown.

Development of low AC loss windings for superconducting traction transformer

We have been developing a light weight 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 2004. We performed the type-test, the system-test, and the vibration-test. Consequently, we could verify that the transformer satisfied the requirement almost exactly as initially planned. However, there have been raised some problems to be solved to put superconducting traction transformer into practical use such that AC loss of the superconducting tape must be lower and the capacity of the refrigerator must be larger. Especially it is the most important to reduce the AC loss of superconducting windings for lightweight and high efficiency. The AC loss must be reduced near the theoretical value of superconducting tape with multifilament. In this study, we fabricated and evaluated the Bi2223 tapes as introduced various measures to reduce the AC loss. We confirmed that the AC loss of the narrow type of Bi2223 tapes with twist of filaments is lower, and we fabricated windings of this tape for use in superconducting traction transformer.

Preliminary study of superconducting transformers for electric rolling stocks

The development of a thousand-meter class flexible wire has been achieved in silver sheathed Bi(Pb)SrCaCuO based superconducting wires, which show a high Jc at relatively low temperatures up to 77 K. A high-Tc superconducting power transformer has been demonstrated recently, and it is expected as one of the superconducting wire applications. Reducing the weight of rolling stocks is a very important issue in railways. Therefore, we discuss the possibility of a promising superconducting power transformer for electric rolling stocks in conventional railways.

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.

Characteristics of Model Windings of High‐TC Superconducting Transformer for Railway Rolling Stock

We investigated the possibility of applying high‐TC superconducting traction transformer to a rolling stock. In order to achieve a lightweight design, the traction transformer needs to have a special winding structure unlike the experimental high‐TC superconducting power transformers fabricated so far. The windings of the traction transformer need to be arranged as closely as possible in a high magnetic field. Then, we fabricated two high‐TC superconducting coils that simulated the winding of a high‐TC superconducting traction transformer. One is a multi‐layer solenoid coil that simulated the primary winding of the transformer. This coil has five layers of a single Bi2Sr2Ca2Cu3Ox (Bi2223) superconducting tape. The other is a close solenoid coil that simulated the secondary winding of the transformer. This coil has one layer of eight parallel Bi2223 superconducting tapes. In this study, we measured the voltage‐current, AC loss, current sharing and over current characteristics of these coils cooled by satur...

Narrow and Standard Gauge Lines Operations

This article illustrates a novel design of traction power converter and the specified control strategy of traction equipment of the GCT. We also introduce the test results to verify the basic function of the propulsion system and refer to the operating results in the gauge changing section to verify the control strategy.