The measurements of temperature dependence of AC magnetic susceptibility were used to study the influence of inhomogeneities on intragranular superconducting properties of Y Ba2Cu3−XMXOY (M=Fe,X=0,005;Al,X=0,01;Cr, X=0,01), Bi1,7Pb0,2Sb0,1Sr2Ca2Cu3OY and Bi1,5Pb0,3Sb0,2Sr2Ca2Cu3OY ceramics. It is found that step-like regions are revealed on AC magnetic field dependence curves T g m(h0) of hyste...

We report on marked memory effects in the vortex system of twinned YBa2Cu3O7 single crystals observed in ac susceptibility measurements. We show that the vortex system can be trapped in different metastable states with variable degree of order arising in response to different system histories. The pressure exerted by the oscillating ac field assists the vortex system in ordering, locally reduci...

This project proposes a novel three phase nine switch AC/AC converter topology. This converter features sinusoidal inputs and outputs, unity power factor, and more importantly, low manufacturing cost. The Operating principle of the Converter is elaborated, its modulation schemes are also discussed, and experimental results from a 5kVA prototype system are provided.

The purpose of this paper is to show the working limits of a Variable Speed Wind Turbine. The system is based on a Doubly-Fed Induction Generator and a Fixed-Pitch Wind Turbine. The machine rotor is connected to the network through an AC/AC Converter in order to allow energy recovery. Thermal, mechanical and electric limits are investigated. The study of the machine is based on a steady state m...

Railway traction is a more stochastic heavy load connected system. Due to the usage of ac-dc converters and ac-ac converters, the various power quality issues become the major problems in the electric system. This paper presents a review on power quality conditioners suitable for Railway traction based on the configuration, components involved and on the technical and economic considerations. M...

A complete study of the ac response of Hg-based superconductors with 1, 2, and 3 Cu-O planes is presented. Under a dc field, the ac susceptibility xac(T) displays a double transition, which is argued to be of intrinsic nature. The systematic analysis of the evolution of xac ~fundamental and higher harmonics! as a function of the experimental parameters, and the comparison with resistance and dc...

Method in which lock-in detectors process signals from standard ac susceptometers, particularly in the detection of higher harmonics, is analyzed in details. The exact formulas have been derived and checked experimentally by measurements on soft ferromagnetic sample, using several available lock-in amplifiers. The reasons why the proper phase adjustment has to be implemented in the protocol of ...

In an attempt to correlate the performance of superconducting radiofrequency cavities made of niobium with the superconducting properties, we present the results of the magnetization and ac susceptibility of the niobium used in the superconducting radiofrequency cavity fabrication. The samples were subjected to buffer chemical polishing (BCP) surface and high temperature heat treatments, typica...