Major issues of NBI power supplies are a high-speed switching, regulation and transmission of dc ultra high voltage, and suppression of surge energy input to the beam source at breakdown. A GTO(gate turn off thyristor) inverter type power supply where the control is performed at low voltage ac side was designed for the ITER NB. Based on the remarkable progress of a high power IEGT (injection enhanced gate transistor), the design of the inverter has been modified to increase an efficiency and compactness using such new elements. A power loss in the inverter is reduced to be 30% of the GTO inverter system. For the transmission line of the dc UHV with intermediate voltages, a disk shape multi-conductor bushing with a transmission line test chamber has been developed. Dimensions of the bushing are 1.8 m in diameter and 140 mm in thickness at the edge. Electric fields at the conductor surface and insulator surface were designed to be lower than 5 kV/mm and 7 kV/mm, respectively. An electric field at the bottom of the ground potential outer conductor was designed to be lower than 1.2 kV/mm to prevent particle levitation which triggers breakdowns. The prototype transmission line has passed the standard impulse test up to 1,300 kV. A dc UHV up to 1,175 kV was successfully sustained for 300 s. To prevent the electric damage of the beam source at the breakdown, core snubbers using Fe-based nanocrystalline soft magnetic materials are adopted to dissipate the surge energy. 1) Hitachi Ltd. , 2) Toshiba Co.
The superconducting magnetic energy storage system (SMES) of output 5 MVA has been developed to bridge instantaneous voltage dips. The field examination is executed by setting up this system at the new and large liquid crystal factory in Japan. The developed SMES system can store up to 7.34 MJ of magnetic energy in superconducting coils using the NbTi Rutherford conductor. The maximum output of the developed SMES is 5 MVA, and the system can discharge the output for one s. The operating current of the coil is 2.7 kA, and the rated voltage is 2.5 kV. The field examination was started in July 2003. During the field test, we will confirm the performance of bridging instantaneous voltage dips by SMES, the long-term drive reliability and the standby loss characteristic.Index Terms-Compact cryo-cooler, field test, instantaneous voltage dips, superconducting magnetic energy storage system (SMES).
This paper describes the development of a vacuum switch carrying a continuous current of 36 kA DC. This switch consists of three vacuum interrupters connected in paralle1.U Generally, it is required to reduce the resistive loss and to increase the heat removal capability for increasing the current carrying capability of VCB. Then, maximizing the cross section of the conductor, and shortening the current path are principally important. However, a coil structure, which produces an axial magnetic field to extinguish the arc stably, makes it difficult due to the geometric complexity. Then, we adopted unique design of the coil structure to solve this difficulty. The newly developed vacuum interrupter is possible to carry current of 8 kA without any cooling, which is twice of the largest VCB available at present in the world. Moreover, introducing the forced-air cooling enhanced the performance up to 12 kA by improving the cooling efficiency. They are verified at a heat running test.
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