Xianzhong Duan

The Pulsed High Magnetic Field Facility at HUST, Wuhan, China and Associated Magnets

A pulsed high magnetic field laboratory has been funded to be established at the Huazhong University of Science and Technology (HUST), Wuhan, China by the National Development and Reform Committee. The facility is planned to be open for external users in 2011 with the implementation of various experimental techniques in pulsed magnetic fields up to 80 T. Pulse durations are in the range from 15 to 1000 ms with the magnet bore sizes from 12 to 34 mm. The pulsed power supplies are a 12 MJ, 25 kV capacitor bank and a 100 MVA/100 MJ flywheel pulse generator. The design and analysis of the power supplies and the magnets of short and long pulse durations and the multi-stage pulsed magnets with controllable waveforms are presented in this paper.

Control scheme studies of voltage source type superconducting magnetic energy storage (SMES) under asymmetrical voltage

Symmetry of system voltage is very important to the performance of superconducting magnetic energy storage (SMES). Both theoretical analysis and simulation results show that, negative sequence current and 2nd harmonic power will be injected into the system, when conventional symmetrical fire is used in power conditioning system (PCS) of SMES. Two indices are used to evaluate the performance of PCS of SMES: the relative error of average value and 2nd harmonic component of active power supplied by SMES. To improve the performance of SMES, symmetrical vector control is put forward in this paper. According to the objective, there are three kinds of symmetrical vector control: positive sequence voltage control, zero negative sequence current control and constant active power control. Their principles are presented and improvements on the performance of SMES are verified by electromagnetic transient simulation. It shows that all those three methods decrease the relative error of average value of active power supplied by SMES. Zero negative sequence current control and constant active power control can also limit the relative error of 2nd harmonic component of active power supplied by SMES effectively.

Design of a 135 MW Power Supply for a 50 T Pulsed Magnet

The National High Magnetic Field Laboratory at Los Alamos designs a magnet that produces magnetic fields of up to 60 T for as long as 100 ms. The power and energy to operate the magnet is provided by a 1430 MVA, 24 kV energy storage generator. Three modular design power supplies convert the AC-power produced by the generator into controlled DC-power needed by the three coil groups of the eight coil magnet. The modules are rated at 4 kV no-load voltage and 20 kA full-load current for up to 2 seconds once every hour, each including a 12-pulse, line-commutated rectifier designed to operate in the 66 Hz to 42 Hz pulse operation range of the generator. A short description of the overall 60 T/100 ms magnet system is given, followed by a detailed description of the the power converter system design. >

Prototype Test and Manufacture of a Modular 12.5 MJ Capacitive Pulsed Power Supply

A new Pulsed High Magnetic Field Facility (PHMFF) is under construction at the Huazhong University of Science and Technology (HUST) in Wuhan, China. In order to provide a wide spectrum range, a modular capacitive pulsed power supply is designed to energize 12.5 MJ at 25 kV and a large variety of coils are designed for magnetic fields in the 50-80 T with pulse duration 15-200 ms, respectively. In order to energize multi-coil systems, the 12.5 MJ power supply is divided into 11 independent 1 MJ modules with a short circuit current of 44.7 kA each and 2 independent 0.75 MJ modules for 61.2 kA each. Each module is provided with its own protection inductor, thyristor switch, crowbar circuit, dump circuit, polarity-changing circuit, charging unit and switchgear. The current pulses can be modified in shape, amplitude and duration by varying the charging voltage, the number of modules and the crowbar resistors. For verifying the design scheme and gaining experience in the construction and operation of pulsed power supply, a 1 MJ prototype that is used to energize pulsed magnets for 50-72 T fields with reversible polarity has been developed. In this paper, after the introduction of the system configuration with different module types and system settings, the design of both the 1 MJ and 0.75 MJ modules is described in detail. Finally, test results of the 1 MJ prototype are presented.

Short and Long Pulse High Magnetic Field Facility at the Wuhan National High Magnetic Field Center

The pulsed high magnetic field facility funded by the Chinese National Development and Reformation Committee has been developed at the Wuhan National High Magnetic Field Center (WHMFC). Magnets of short pulse, long pulse and the combination of both with bore sizes from 12 to 34 mm have been developed and are operational for electric transport, magnetization, magneto-optics and electron spin resonance at temperatures in the range from 100 mK to 350 K. The power supplies for these magnets consist of a capacitor bank with 12 modules of 1 MJ/25 kV each and 2 modules of 0.8 MJ/25 kV each, a 100 MVA/100 MJ flywheel pulse generator and a 771 V/180 kAh battery bank. A dual-coil magnet driven by the capacitor banks has successfully generated 86.3 T field with a total pulse duration over 350 ms in a 12-mm bore. A dual-coil long pulse magnet wound from soft copper wire energized by the flywheel generator produces 50 T peak field with a 100 ms flat-top and a total 1.1 s pulse duration in a 22 mm bore. A battery bank driven long pulse magnet composed by the series connection of two nested coils generates 32 T peak field with the pulse duration of 1.5 s in a 21-mm bore.

The Development of High Performance Pulsed Magnets of the Prototype Facility of WHMFC

Coils for pulsed magnets in the range of 50-75 T are developed with optimized combinations of conductors and reinforcement for the prototype laboratory of the Wuhan High Magnetic Field Center (WHMFC). The basic design tool is a Pulsed Magnet Design Software package (PMDS) for calculating the capacitor discharge, conductor heating, mechanical stresses and the residual stress, including plastic deformation and winding tension. A 1 MJ capacitor bank is equipped with a thyristor switch, a mechanical switch, polarity reversal switches, a current limiting inductor and a diode crowbar. The design and the test results of the magnets, of the protection inductance and of the capacitor bank are presented and discussed in this paper.

Testing and Commissioning of a 135 MW Pulsed Power Supply at the Wuhan National High Magnetic Field Center

At the Wuhan National High Magnetic Field Center, two 67.5-MW pulsed power supply units have been installed to energize long-pulse magnets. Each unit based on a 12-pulse converter consists of two 6.9 kV/1.2 kV (1.0 kV) cast coil transformers and two six-pulse rectifiers connected in series. The units are connected to a 100 MVA/185 MJ inertial energy storage motor-generator set and can operate independently as well as in parallel or in series. Each unit is designed to provide no-load voltages of 3.2 kV (2.7 kV) and full-load voltages of 2.7 kV (2.25 kV) at the rated current of 25 kA for a 3-s pulse once every half hour. After completion of various performance tests, the power supply commissioning started in October 2012. At present, the power supply has energized a long-pulse magnet more than 100 times to produce flat-top pulses at various field levels, including a 50-T field pulse with 100-ms flat-top duration. In this paper, the final design of the power supply components is described in detail. Testing and commissioning results of the power supply taken with a dummy load and a long-pulse magnet are also presented.

Design and Analysis of a Combined Power Supply for High-Field Quasi-Continuous Magnets

The high-field quasi-continuous magnets (QCM) are of great interest for scientific experiments that require long pulse duration and in particular a field pulse with a flat-top. For the QCM, the power supply is a real challenge. At the Wuhan National High Magnetic Field Center (WHMFC), it is planned to realize a 45 T/500 ms flat-top field by the series combination of a 0.6 kV/35 kA battery bank and a 12-pulse rectifier that is powered by a 100 MVA/100 MJ flywheel pulse generator (FPG). In order to reduce the dc current ripple, a dc passive filter is connected in parallel with the rectifier. The simulation of the pulse shape with respect to the voltage profile supplied by the power supply takes the resistance of the magnet into account; this increases with temperature as a function of coil current. The configuration and the associated control strategy are presented in this paper. A simulation model of the combined power supply system is developed and compared with the model of a single rectifier supply system. Results are provided to validate the proposed method.