Nanocrystalline Magnesium ferrite has been prepared by chemical co-precipitation technique. Structural characterization has been performed by X-ray diffraction. Formation of ferrites has also been studied by using FTI...Nanocrystalline Magnesium ferrite has been prepared by chemical co-precipitation technique. Structural characterization has been performed by X-ray diffraction. Formation of ferrites has also been studied by using FTIR. Frequency dependence of real and imaginary part of initial permeability has been presented for the samples sintered at different temperatures. Real part of initial permeability, increases with the increase of grain growth. The loss component repre- sented by imaginary part of initial permeability decreases with frequency up to the measured frequency of this study of 13 MHz. Curie temperatures have been determined from the temperature dependence of permeability. Curie temperatures for the samples of this composition do not vary significantly with the variation of sintering temperatures. B-H loop measurements have been carried out by B-H loop tracer. Transport property measurements haven been carried out by electrometer and impedance analyzer.展开更多
According to the B-H curve and structural dimensions of the snubber by the Fink- Baker Method, the inductive voltage and the eddy current of any core tape with the thickness of the saturated regions are derived when t...According to the B-H curve and structural dimensions of the snubber by the Fink- Baker Method, the inductive voltage and the eddy current of any core tape with the thickness of the saturated regions are derived when the accelerator breakdown occurs. Using the Ampere＇s law, in each core tape, the eddy current of the core lamination is equal to the arc current, and the relation of the thickness of the saturated regions for different laminations can be deduced. The total equivalent resistance of the snubber can be obtained. The transient eddy current model based on the stray capacitance and the equivalent resistance is analyzed, and the solving process is given in detail. The exponential time constant and the arc current are obtained. Then, the maximum width of the lamination and the minimum thickness of the core tape are determined. The experimental time constant of the eddy current obtained, with or without the bias current, is approximately the same as that by the analytical method, which proves the accuracy of the adopted assumptions and the analysis method.展开更多
A transformer type iron core snubber, as a protective device against the stray capacitance during the breakdown in EAST, is analyzed in detail. Three kinds of topology are presented. Then with the analysis for equival...A transformer type iron core snubber, as a protective device against the stray capacitance during the breakdown in EAST, is analyzed in detail. Three kinds of topology are presented. Then with the analysis for equivalent circuit, the ranges of three key parameters, i.e., secondary side resistance, leakage inductance and snubber inductance, are determined. By con- sidering the saturation of the magnetic material, a design principle is Mso presented. A nearly 1：10 core snubber is tested. It is proved that a high permeability core with secondary resistor can restrain the discharge current effectively.展开更多
The core snubber, as a passive protection device, can suppress arc current and absorb stored energy in stray capacitance during the electrical breakdown in accelerating electrodes of ITER NBI. In order to design the c...The core snubber, as a passive protection device, can suppress arc current and absorb stored energy in stray capacitance during the electrical breakdown in accelerating electrodes of ITER NBI. In order to design the core snubber of ITER, the control parameters of the arc peak current have been firstly analyzed by the Fink-Baker-Owren （FBO） method, which are used for designing the DIIID 100 kV snubber. The B-H curve can be derived from the measured voltage and current waveforms, and the hysteresis loss of the core snubber can be derived using the revised parallelogram method. The core snubber can be a simplified representation as an equivalent parallel resistance and inductance, which has been neglected by the FBO method. A simulation code including the parallel equivalent resistance and inductance has been set up. The simulation and experiments result in dramatically large arc shorting currents due to the parallel inductance effect. The case shows that the core snubber utilizing the FBO method gives more compact design.展开更多
文摘Nanocrystalline Magnesium ferrite has been prepared by chemical co-precipitation technique. Structural characterization has been performed by X-ray diffraction. Formation of ferrites has also been studied by using FTIR. Frequency dependence of real and imaginary part of initial permeability has been presented for the samples sintered at different temperatures. Real part of initial permeability, increases with the increase of grain growth. The loss component repre- sented by imaginary part of initial permeability decreases with frequency up to the measured frequency of this study of 13 MHz. Curie temperatures have been determined from the temperature dependence of permeability. Curie temperatures for the samples of this composition do not vary significantly with the variation of sintering temperatures. B-H loop measurements have been carried out by B-H loop tracer. Transport property measurements haven been carried out by electrometer and impedance analyzer.
基金supported by Research Fund for the Doctoral Program of Higher Education of China (No.20060248012)Shanghai-Canada Research Council cooperation (06SN07113)Auxiliary Heating Project of EAST upgrade, National Program on Key Basic Research Project (973 Program) of China (No.2010GB108003)
文摘According to the B-H curve and structural dimensions of the snubber by the Fink- Baker Method, the inductive voltage and the eddy current of any core tape with the thickness of the saturated regions are derived when the accelerator breakdown occurs. Using the Ampere＇s law, in each core tape, the eddy current of the core lamination is equal to the arc current, and the relation of the thickness of the saturated regions for different laminations can be deduced. The total equivalent resistance of the snubber can be obtained. The transient eddy current model based on the stray capacitance and the equivalent resistance is analyzed, and the solving process is given in detail. The exponential time constant and the arc current are obtained. Then, the maximum width of the lamination and the minimum thickness of the core tape are determined. The experimental time constant of the eddy current obtained, with or without the bias current, is approximately the same as that by the analytical method, which proves the accuracy of the adopted assumptions and the analysis method.
基金supported in part by Auxiliary Heating Project of EAST upgradein part by Ph. D foundation of State Education Ministry of China(No. 20060248012)
文摘A transformer type iron core snubber, as a protective device against the stray capacitance during the breakdown in EAST, is analyzed in detail. Three kinds of topology are presented. Then with the analysis for equivalent circuit, the ranges of three key parameters, i.e., secondary side resistance, leakage inductance and snubber inductance, are determined. By con- sidering the saturation of the magnetic material, a design principle is Mso presented. A nearly 1：10 core snubber is tested. It is proved that a high permeability core with secondary resistor can restrain the discharge current effectively.
基金supported by National Program on Key Basic Research Project of ITER Core Snubber in China (973 Program) (No.2010GB108003)
文摘The core snubber, as a passive protection device, can suppress arc current and absorb stored energy in stray capacitance during the electrical breakdown in accelerating electrodes of ITER NBI. In order to design the core snubber of ITER, the control parameters of the arc peak current have been firstly analyzed by the Fink-Baker-Owren （FBO） method, which are used for designing the DIIID 100 kV snubber. The B-H curve can be derived from the measured voltage and current waveforms, and the hysteresis loss of the core snubber can be derived using the revised parallelogram method. The core snubber can be a simplified representation as an equivalent parallel resistance and inductance, which has been neglected by the FBO method. A simulation code including the parallel equivalent resistance and inductance has been set up. The simulation and experiments result in dramatically large arc shorting currents due to the parallel inductance effect. The case shows that the core snubber utilizing the FBO method gives more compact design.
