Analysis of turbine generator steady-state reactances for load conditions

This paper describes variations of turbine generator steady-state reactances for load conditions. When the turbine generator is of small size, magnetic saturation of the stator and rotor core is a problem. Therefore, it is important to understand the variations of the reactances for load conditions. The reactances of a 592-MVA turbine generator are calculated with d- and q-axis equations considering magnetic saturation and two-dimensional numerical magnetic field analysis. The results are as follows. (1) The equivalent synchronous reactances considering cross-magnetizing are smaller than the original synchronous reactances for load conditions. (2) Numerical values of the d- and q-axis mutual reactance and the field and q-axis mutual reactance are at their maximum when the d-axis linkage flux is nearly equal to the q-axis linkage flux under constant voltage. (3) The d-axis synchronous reactance drops with increasing reactive power under constant voltage and active power, but the q-axis synchronous reactance increases. (4) The variation of the equivalent d-axis synchronous reactance with increasing reactive power is similar to that of the d-axis synchronous reactance, but the variation of the equivalent q-axis synchronous reactance is different from that of the q-axis synchronous reactance. © 1998 Scripta Technica. Electr Eng Jpn, 123(3): 73–83, 1998     

Analysis of terminal voltage waveform of AC exciting synchronous generators

Recently, adjustable speed hydroelectric power systems have been developed. In those power systems, ac exciting synchronous generators are used instead of the ordinary salient-pole-type synchronous machines. However, some higher harmonic sequences are included in the distribution of air-gap magnetic flux density and in the terminal voltage waveform of the ac exciting synchronous machines because these machines have open winding slots. To develop better machines without terminal voltage waveform distortions, an evaluation method of the terminal voltage harmonics has been needed. This paper describes the mechanism of higher harmonics generation qualitatively and proposes an analytical method of no-load terminal voltage waveforms on the basis of two-dimensional magnetic field analysis considering movement of the rotor for quantitative higher harmonics analysis. The analytical results of higher harmonics show good agreement with the experimental ones.     

Circuits to reduce distortion in the diode-bridge track-and-hold

Circuits for reducing distortion in the diode-bridge track-and-hold are described. Adding circuits with current and voltage feedback can reduce distortion caused by the droop and nonlinear junction capacitance of a transistor. A high-speed complementary bipolar process technology is incorporated in the circuit design for its flexibility. SPICE II simulation demonstrates that the circuits reduce distortion in the diode-bridge track-and-hold by 10 to 20 dB     

Graphitization behavior of the implanted furan-resin-derived carbon

Ar or Xe ions were implanted into the fractured-faces or surfaces of as-carbonized glass-like carbon (GC) specimens for modification of the structure of them. Microstructural changes were examined by Raman spectroscopy, by scanning tunneling microscope (STM) and by transmission electron microscopy (TEM). It was found that the as-carbonized surfaces and fractured-faces of the specimens were changed to an amorphous structure by ion implantation. Implanted as-carbonized surfaces of specimens were restored nearly pristine structures after re-heat-treatment at 3000 °C. On the other hand, implanted fractured-faces of specimens resulted in well-developed structures after re-heat-treatment at 3000 °C. After re-heat-treatment at 3000 °C, the degree of graphitization on the implanted fractured-faces was higher than that on the pristine fractured-faces. It can be concluded that mobility of carbon atoms, or free face, seemed to play an important role on surface graphitization.     

Suppression of 193-nm photoresist deformation by H2 addition to fluorocarbon plasma in via-hole etching

Suppression of 193-nm photoresist deformation by H₂ addition to fluorocarbon plasmas in via-hole etching is investigated for sub-65-nm-node dual-damascene patterning. Photoresist deformation causes profile distortion and results in degradation of reliability, such as the line-to-line time dependent dielectric breakdown. To prevent profile distortion, H₂ addition to fluorocarbon plasma is investigated in terms of fluorocarbon polymer and photoresist modification. XPS, FT-IR, and highlight etching investigations reveal that the H₂ plasma treatment extracts oxygen from the photoresist and modifies it. This modification suppresses the photoresist deformation and H₂ addition to fluorocarbon plasmas can have the same effects as the H₂ plasma treatment. Finally, a highly reliable damascene interconnection is successfully achieved.     

Combined effects of Cordyceps sinensis and methotrexate on hematogenic lung metastasis in mice

We investigated antitumor effects of water extracts of Cordyceps sinensis (WECS). WECS (100 microg/ml) induced apoptosis of B16 melanoma cells after 48 h exposure in vitro as determined by both the TUNEL (TdT-mediated dUTP-biotin nick end labeling) method and the detection of a DNA ladder. In vivo, combined treatment with WECS and methotrexate (MTX) in mice intravenously inoculated with B16 melanoma cells was conducted. Although MTX caused a significant and severe decrease in body weight compared with that in control mice starting 16 days after the start of administration, the mice given both MTX and WECS did not show a significant decrease in body weight. The mean survival time (days) of the control mice, MTX-treated mice (15 mg/kg/day, s.c.), and WECS-treated mice (200 mg/kg/day, p.o.) was 25.0 +/- 0.3, 25.6 +/- 1.3, and 25.7 +/- 1.0 (mean +/- S.E.M. of 6-7 mice), respectively. On the other hand, mean survival time (days) of mice given the combination of MTX and WECS was 28.2 +/- 0.7, significantly longer than the control value. WECS might be beneficial in the prevention of tumor metastasis as an adjuvant agent in cancer chemotherapy.     

Anisotropic Superconducting Properties of MgB2 and Related Compounds

Anisotropic superconducting properties of inter-metallic compounds MgB₂, Y₂PdGe₃, and CaAlSi with AlB₂ structure are studied by detailed angular dependent transport measurements. MgB₂ and CaAlSi shows appreciable anisotropy of the upper critical field, H _c2, with mass anisotropy parameter =3 and 2, respectively, while Y₂PdGe₃ is almost isotropic. In-plane anisotropy of H _c2 in these hexagonal superconductors is very small, consistent with the prediction based on GL theory.     

A new experimental technique for determinations of the activities of P<Subscript>2</Subscript>O<Subscript>5</Subscript> and Fe<Subscript>x</Subscript>O—the system CaO-P<Subscript>2</Subscript>O<Subscript>5</Subscript>-Fe<Subscript>x</Subscript>O

An experimental technique was applied for simultaneous determinations of the activities of P₂O₅ and Fe_xO in slags. With this technique, phosphorus-containing liquid copper was heated inside an iron crucible at temperatures below 1600 K. When copper is melted, the iron crucible dissolves into liquid copper, to a small extent, to form ternary {Cu-Fe-P} liquid alloy, while 〈Cu-Fe-P〉 solid solutions are formed on the inner wall of the iron crucible. Slags containing tri-calcium phosphate were then brought into equilibrium with {Cu-Fe-P} liquid alloy. By measuring the equilibrium oxygen partial pressures with the aid of a zirconia electrolyte cell, activities of P₂O₅ and Fe_xO were obtainable. Between 1553 and 1593 K, the P₂O₅ activities could be expressed as

A 10-GHz 8-b multiplexer/demultiplexer chip set for the SONETSTS-192 system

An ultrahigh-speed 8-b multiplexer (MUX) and demultiplexer (DMUX) chip set has been developed for the synchronous optical network (SONET) next-generation optical-fiber communication systems, which will require data bit rates of about 10 Gb/s. These ICs were designed using three novel concepts: a tree-type architecture giving reliable operation, a dynamic divider with a wide operating range, and a 50-Ω on-chip transmission line with high-speed pulse propagation. They were fabricated using a 0.5-μm WN_x-gate GaAs MESFET process. The DMUX and MUX operated at up to 10.4 and 11.4 GHz, respectively, both with an adequate phase margin of more than 230°     

Interface reactions between SiO2-PbO glass and Ni-Zn ferrite

The interface reactions between SiO₂-PbO melt and Ni-Zn ferrite were studied using electron probe microanalysis and X-ray diffraction. The mechanisms of interface reaction were investigated in relation to the glass-forming region. No intermediate layers were produced at the interface between SiO₂-PbO glass and Ni-Zn ferrite because of the small amount of dissolution of Ni²⁺ ion from the ferrite. A model of the interface reaction mechanism between SiO₂-PbO melt and Ni-Zn ferrite is proposed.