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Qiu L.,Wuhan Pulsed High Magnetic Field Center | Lv Y.,Wuhan Pulsed High Magnetic Field Center | Li L.,Wuhan Pulsed High Magnetic Field Center
IEEE Transactions on Applied Superconductivity | Year: 2010

The protection inductor serves for limiting the peak current in order to protect the thyristor switch of the pulsed magnetic field facility in case of a short circuit. Because of the high current and strong magnetic field, the Lorentz force in the protection inductor is large. This paper describes the calculation of the inductance and the optimization of the stresses in the protection inductor. A finite element analysis with the ANSYS software is used to calculate the magnetic field and stresses in the protection inductor. A three-dimensional static finite element analysis model of the inductor has been built for calculating the stresses in the copper coils and stainless steel rings as well as the static inductance. Furthermore, a harmonic finite element analysis model has been built to analyse effects such as the influence of eddy currents in the copper wires and induced current in the stainless steel rings on stress and inductance. Eddy currents cause an uneven distribution of stresses; induced current can decrease the stresses in the copper coils but increase those in the stainless steel rings. Both effects reduce the inductance. The typical maximum stresses in our design are 70 MPa in the copper coils and 210 MPa in the stainless steel rings; these are both below the yield strength of these materials. The inductance is 1.05 mH at the frequency of 50 Hz. The protection inductor has been manufactured according to the design and the performance testing has been successfully completed. © 2006 IEEE. Source


Lv Y.,Wuhan Pulsed High Magnetic Field Center | Qiu L.,Wuhan Pulsed High Magnetic Field Center | Zhang S.,Wuhan Weite Special Motor Ltd. | Tang Y.,Wuhan Weite Special Motor Ltd. | Li L.,Wuhan Pulsed High Magnetic Field Center
IEEE Transactions on Applied Superconductivity | Year: 2010

A 25 kV/40 kA protection inductor with low stray field was designed and the first prototype was fabricated. The protection inductor protected the thyristor switch in the capacitor bank, limit the current at 40 kA in case of a short circuit. It was designed as a toroidal system consisting of 12 coils evenly distributed in the perimeter of a circle. The inductance could be changed easily by adjusting the number of coils. The structure of coils was optimized to withstand the great electromagnetic force produced by the 40 kA current. The coils were wound by a 4 * 45 mm copper strip standing on edge. Each coil was externally reinforced by a stainless steel ring tightly enclosing the coil. The first prototype was fabricated. Its inductance and magnetic field were tested. The prototype has been mounted in the 1 MJ module and is now in operation. In this paper, the structure design, fabrication and testing of a new protection inductor are presented. The testing results are discussed. Tested inductance was 1.05 mH and direct resistance was 16 mΩ. The first prototype was proved to be successful and 13 more protection inductors will be made after some improvements. © 2006 IEEE. Source


Song Y.,Wuhan Pulsed High Magnetic Field Center | Peng T.,Wuhan Pulsed High Magnetic Field Center | Li L.,Wuhan Pulsed High Magnetic Field Center | Lv Y.,Wuhan Pulsed High Magnetic Field Center | Qiu L.,Wuhan Pulsed High Magnetic Field Center
IEEE Transactions on Applied Superconductivity | Year: 2010

A precise and efficient finite element model has been developed to solve the coupling of the magnetic field and heating in pulsed coils energized by a capacitor bank. The magnetic field and the current density distribution in each conductor layer of the coil are simulated, taking into account the eddy current, magneto-resistance and heat conduction. The temperature distribution in the conductor during the discharge is also calculated. Eddy currents and magneto-resistance result in a large temperature gradient across the layers. The calculated pulsed field waveform is in good agreement with experimental results for a large range of pulsed coils; this provides useful insight for optimized coil design. © 2006 IEEE. Source

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