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Power regenerative controls by utilizing thyristor rectifier of voltage source inverter

A technique for the regenerative control of a voltage source inverter is described. In the proposed equipment, the rectifier bridge is utilized for regeneration through a medium of a DC reactor. Another type of regenerative control that involves a modified Cuk converter method is described. A frequency analysis approach using the switching function is used in order to analyze the output current waveforms. The appropriateness of this theory is experimentally confirmed.<<ETX>>

A reduction method of harmonic currents in power systems generated by switching regulators

A forward power converter with reduced harmonics for the input supply current is proposed. In this converter, the input capacitance is reduced, so that lower-order harmonics such as the fifth and the seventh can be largely reduced by about 20% to 40%. However, the DC link voltage ripple is increased in the proposed circuit. Such characteristics have been improved by a ripple compensation circuit consisting of the feedforward circuit. One can also obtain a noticeable harmonic elimination effect for the use of parallel connection between the proposed circuits and the conventional ones.<<ETX>>

A dual thyristor converter reducing harmonics of power supply without input transformer

A converter is presented which can reduce harmonics like the conventional 12-pulse converters with input three phase transformers. This circuit has the center tapped reactor which controls the DC link current, at different two values. The converter need not use the input three phase transformer that usually makes the cost higher. The proposed circuit has commutation with the capacitor whose commutation is executed successfully with constant reverse bias time. Secondly, the idea of current control with the center tapped reactor is developed for a single phase novel rectifier circuit which reduces the lower order harmonics in the power system.<<ETX>>

Annealing Effect on Resistivity of BiSrCaCu2Oy

The annealing effect on the resistivity and the critical temperature of BiSrCaCu2Oy where the low temperature phase is predominant was examined. The resistivity becomes higher, as increasing the annealing temperature in N2 atmosphere and the sample annealed above 700°C did not show zero resistance from 20 K to 300 K. However, the resistivity and the critical temperature recover nearly the same value as the as-grown sample after annealing in O2 atmosphere.

The effects of Fe doping and forming pressure on the superconducting properties of Bi1.6Pb0.37Sb0.03Sr2Ca2Cu3Oy

This paper discusses the influence of the Fe doping and the forming pressure on the superconducting properties of Bi1.6Pb0.37Sb0.03Sr2Ca2Cu3Oy prepared by the solid‐state reaction. The critical temperature (Tc) obtained from the electrical resistance for the specimens sintered at 850 °C for 200 h, became gradually lower from 107 K to 75 K with increasing a Fe content from 0% to 0.8 wt%.Effect of Fe doping was examined from the magnetization curve measured by using the vibrating sample magnetometer (VSM) at the temperature range from 4.5 K to 77 K. The critical current density (Jc) based on Bean’s model drastically decreased from 3000 A/cm2 at 0 wt% Fe to 50 A/cm2 at 0.8 wt% Fe at zero field. The Jc of the sample without Fe formed at 5000 kg/cm2 and those at 1000 kg/cm2 were 3000 A/cm2 and 700 A/cm2, respectively, indicating that the forming pressure (Pf) is important for an improvement of Jc although it affects little on Tc.This seems to be due to the fact that the higher Pf increases the green density of...

Liquid phase epitaxy of Bi2Sr2CaCu2Oy on the MgO(001) substrate from the KCl solution

Superconducting films of Bi2Sr2CaCu2Oy were epitaxially grown on MgO (001) single crystals using a KCl solvent in an Al2O3 crucible. It was heated at 895 °C and then cooled down to 815 °C at a rate of 3∼8 °C/h rotating the substrate at 0∼60 rpm. The rotation at a proper speed is essential to obtain the good epitaxial layer. At 30 rpm the typical layer thickness was 4 μm and the surface morphology was fairly smooth. The addition of B2O3 in the solution was effective to obtain smoother surface morphology. The best critical temperature was 85K. Critical current density estimated from magnetization curves was 590A/cm2 for the ab plane at zero magnetic field and 77K.

LPE growth of Bi2Sr2CaCu2Oy from KCl solution

Abstract Superconducting films of Bi2Sr2CaCu2Oy were epitaxially grown on MgO (001) single crystals using a KCl solvent. Grown layers were characterized by microscope, XRD and VSM. The film was grown on most of the substrate surface and the surface morphology was fairly smooth. Typical layer thickness was 4 μm. Critical temperature was 85 K from the resistance and the AC susceptibility. Critical current density estimated from magnetization curves was 590 A/cm2 for the ab plane at zero magnetic field and 77 K.