Showing papers by "Hiroaki Tsutsui published in 2007"

Power factor correction using magnetic energy recovery current switches

Abstract: In this paper, we propose a Magnetic Energy Recovery Switch (MERS). The switch consists of four MOSFET elements and one capacitor. A power factor improvement is automatically possible regardless of the impedance and power frequency of the load by synchronized switching of MERS with a power supply. MERS itself generates voltage and compensates for the inductance voltage unlike a conventional series capacitor, so that another DC power supply is not needed. An experiment was carried out to demonstrate the automatic correction of the power factor. We can also expect energy saving of electromachines such as an electric motor by the power factor correction with MERS. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(3): 56–62, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20321

Development of a One Tenth Sized Model Coil for 100-MJ Class SMES Using Force-Balanced Coil Concept

Abstract: A one tenth sized model coil based on the force-balanced coil (FBC) design for 100-MJ class SMES has been designed. This coil is a hand-made coil using NbTi superconductors, and the winding of the model FBC is now in progress. The FBC is a helically wound hybrid coil of toroidal field coils and a solenoid. This coil can minimize the mechanical stress and the required mass of the structure for induced electromagnetic forces. The model FBC with an outer diameter of 0.53 m will have the stored energy of 270 kJ at the maximum magnetic field of 7.0 T. The winding form is made of aluminum alloy and slots are cut on its surface with the shape of the helical winding. From the results of the cooling test with liquid nitrogen, the significant deformations of the winding form have not been observed. The winding of the model coil is carried out without reinforcing materials for the NbTi strand. The in-plane curvature of helical coils causes the winding errors. Then after a slight winding tension is applied to the NbTi strand, each winding is adjusted to be fixed in its place. The experiments will be conducted with liquid helium cooling. The DC power supply for the model FBC can simulate various SMES operations. As a first step, the ramp-rate dependence of the superconducting properties of the model coil will be investigated in order to evaluate the mechanical stress in the helical windings without the reinforcing materials for the NbTi strand.

Burn control simulation experiments in JT-60U

Abstract: Burn control simulation experiments were conducted in non-burning DD plasmas by using a burning plasma simulation scheme in JT-60U In the burning plasma simulation scheme, two neutral beam (NB) groups were used, where one simulates α-particle heating and the other simulates external heating The stored energy and the neutron yield rate were controlled at nearly constant values in both ELMy H-mode plasma and reversed shear (RS) plasma with an Internal Transport Barrier In these plasmas, the NB power for the external heating simulation increased/decreased when the NB power for the α-particle heating simulation decreased/increased Variation of the NB power for the external heating simulation was larger in the RS plasma than that in the ELMy H-mode plasma, indicating that larger control margin is necessary for the RS plasmas In order to understand the detailed physical mechanism for the difference between ELMy H-mode and RS plasmas, we conducted numerical analysis using a 15-dimensional transport code This calculation indicates the larger variation experimentally observed in the RS plasma could not be explained by the difference of the thermal diffusivity profiles or its temperature dependence

Laser Scattering Measurement of the Electron Density Fluctuations in CHS

Abstract: For measurement of electron density fluctuations (up to 1 MHz), an HCN laser scattering measurement system with a super rotating grating was developed o nC HS. When we measured electron density fluctuations with kr = 5. 4c m −1 in a plasma edge region at the outer side of torus, fluctuation spectra which have harmonic components up to the fifth were observed. The fundamental frequency was less than about 60 kHz, which changed during the discharge. The change in frequency correlate db est with the plasma stored energy divided by the line averaged density. An edge transport barrier (ETB), which can improve particle transport in the edge region, has been observed in CHS and the measured fluctuation amplitude also decreases. The fluctuations decreased in about 5m s, and thedecrease of the fluctuations preceded by 3 ms to the drop of Hα emission signal.

Performance test of dual modulator polarimeters in two different configurations for magneto-optic measurement of fusion devices

Abstract: We proposed and tested a new configuration of a magneto-optic polarimeter with a pair of photoelastic modulators (PEMs). In the new configuration, the number of optical components including PEMs can be much smaller than that in a conventional one with PEMs. This paper describes the results of performance test and comparisons to the conventional configuration. The dependences on the light source (a He–Ne laser, 632.8 nm and a superluminescent diode, SLD, 822 nm) are also discussed. The polarization angle can be measured and angle resolution comparable to those in the conventional one was obtained. Angle resolution of 0.002° and 0.07° with a response time of 10 ms was achieved at an incident polarization angle of about 0° and 21°, respectively. The resolution of 0.07° corresponds to 7 G when a 40-mm-long ZnSe sensing rod is used. Linearity of the measured angle against the real one degraded, especially with He–Ne laser, increasing the numbers of the mirrors for beam transmission. On the other hand, the resolution is insensitive to the number of mirrors. Good long-time stability was confirmed with the SLD but a little deterioration was found with the He–Ne laser in the two configurations.