Y. Pan

Thermal Analysis of Air-Core Power Reactors

A fluid-thermal coupled analysis based on FEM is conducted. The inner structure of the coils is built with consideration of both the structural details and the simplicity; thus, the detailed heat conduction process is coupled with the computational fluid dynamics in the thermal computation of air-core reactors. According to the simulation results, 2D temperature distribution results are given and proved by the thermal test results of a prototype. Then the temperature results are used to calculate the heat flux to predict the detailed heat transfer process in the packages of the reactors. The study in this paper may be useful in the design optimization in air-core reactors.

New printed circuit boards magnetic coils in the vacuum vessel of J-TEXT tokamak for position measurement

Four sets of magnetic diagnostic coils, which are printed on machinable ceramic printed circuit boards (PCB), are designed, fabricated, installed, and tested in the Joint Texas Experimental Tokamak (J-TEXT) vacuum vessel for detecting the plasma radial and vertical displacements relative to the geometric center of the vacuum vessel in Ohmic discharges. Each coordinate is determined by a pair of variable cross-section Rogowski and saddle coils, which measure the tangential and normal magnetic fields (relative to the coil surface). These coils are suitable for mass production and offer advantages in vacuum compatibility and temperature tolerance that are important for J-TEXT. Position measurements using PCB coils are compared with those from soft x-ray image system and match the position well.

Research on ultra-fast vacuum mechanical switch driven by repulsive force actuator

In order to meet the fast operation demands of DC circuit breakers, a high-speed vacuum mechanical switch (VMS) driven by a repulsive force actuator is focused. To improve the drive speed and energy conversion efficiency (ECE) of the actuators, the dynamic characteristics of the double sided coil repulsive force actuators are investigated, and two generalized optimization design methods focusing on the aspect ratio of the driving coils (defined as ARF) and the electrical parameters (defined as EF) are developed. FEM simulation models simulation and tests of VMS prototypes are conducted to verify the optimization methods. Results prove that the ARF method could improve the ECE of a VMS from 1.05% to 7.55%, and EF method could improve ECE of the same VMS from 1.05% to 6.61%, the combination of ARF and EF could improve the value of VMSs ECE to 10.50%, thus proving the validity and accuracy of the optimization methods.

A comparison of contact erosion for two types arcing contact of SF6 circuit breakers in making process

The paper presents the results of making tests of arcing contact made from copper-tungsten (Cu-W) composites containing different contents of tungsten: 80% and 85%. The Cu-W arcing contacts are tested in a SF6 circuit breaker under the condition that the making velocity is 7m/s and the current peak is 18kA. The arcing time of every making test is measured. The electrical properties of the contacts are tested every 20 making operations and the mass loss is investigated after 100 operations. It is determined that the two types of Cu-W contacts have different electrical properties, in other words, their efficacy can be determined for the making as arcing contacts for an SF6 circuit breaker.

A novel method to optimize the mode spectrum of the dynamic resonant magnetic perturbation on the J-TEXT tokamak

The dynamic resonant magnetic perturbation (DRMP) system has been developed for the J-TEXT tokamak to study the interaction between the rotating perturbation magnetic field and the plasma. When the DRMP coils are energized by two phase sinusoidal currents with the same frequency, a 2/1 rotating resonant magnetic perturbation component will be generated. But at the same time, a small perturbation component rotating in the opposite direction is also produced because of the control error of the currents. This small component has bad influence on the experiment investigations. Actually, the mode spectrum of the generated DRMP can be optimized with an accurate control of phase difference between the two currents. In this paper, a new phase control method based on a novel all-digital phase-locked loop (ADPLL) is proposed. The proposed method features accurate phase control and flexible phase adjustment. Modeling and analysis of the proposed ADPLL is presented to guide the design of the parameters of the phase controller in order to obtain a better performance. Testing results verify the effectiveness of the ADPLL and validity of the method applying to the DRMP system.

Reconstruction Progress of the COMPASS-D ECRH System on J-TEXT

To make the J-TEXT tokamak more flexible for physics experiments, an electron cyclotron resonance heating (ECRH) system is being developed. The main parts of the J-TEXT ECRH system are donated by the Culham Science Center from the former COMPASS-D, including six 60 GHz/200 kW/5 s (0.5 s) gyrotrons, six magnets, and auxiliary power supplies for the gyrotrons, transmission parts, and so on. For the ECRH system, the output mode of the gyrotron from the former Varian Associates, Inc. is TE02 mode and converted to TE01 mode for low loss transmission. The TE01-TE11-HE11 mode converter is used at the end of the transmission lines for efficient coupling. Then, the high-power wave is injected to the desired area of the plasma by a rotatable quasi-optical launcher. A 100 kV/60 A power supply based on a pulse step modulation technology has been developed to feed all the gyrotrons. The control system based on the compact reconfigurable I/O-9068 platform of National Instruments for monitoring, timing, and protection is being designed. Other units, such as the cooling loops, the launcher, and a spared auxiliary power supply, are on the way. We hope that four subsystems can be finally used on J-TEXT.

Design of variable-frequency power supply system based on multilevel inverters for dynamic resonant magnetic perturbation coils on J-TEXT tokamak

The dynamic resonant magnetic perturbation (DRMP) coils have been designed to study the feedback control of tearing mode (TM) instability in J-TEXT tokamak with rotating resonant magnetic perturbation. The AC power supply system energizing coils should have the ability of controlled current frequency in the range of 1 kHz to 5 kHz and amplitude of 5 kA peak value at 5 kHz. In further study, TM will be feedback controlled. In this paper, the main circuit of the variable-frequency power supply system with thyristor rectifier and cascaded H-bridges multilevel inverter is proposed. In order to adapt for the digital feedback control, a fast algorithm to calculate conduction angles of cascaded inverter is emphasized. Experimental results of the main circuit prototype are presented in the end of this paper.

Modeling and analysis of the inverter type high voltage power supply with duty cycle modulation

The acceleration grid power supply (AGPS) is an important part of neutral beam injector (NBI) system. With the increasing of the NBI power, the requirement for output voltage of the AGPS is becoming higher and higher, even reaching to 1000 kV. As the Inverter type high voltage power supply uses the inverters located at lower voltage side to regulate and cut off the output voltage, its very suitable for high voltage applications. The advised scheme for the AGPS of ITER NBI system is composed of five stages, each stage is an inverter type power supply with an output voltage of 200 kV. This paper investigates the inverter type power supply based on neutral point clamped (NPC) three phase three level (TPTL) inverter and three phase step-up transformer, which is equivalent to an insulated TPTL dc-dc converter connected with a dual dc link. In order to design a preferable controller for the inverter type power supply, the topology and principles of the TPTL dc-dc converter with duty cycle modulation has been analyzed. Our results indicate that only when the converter operates at a large duty cycle, the output voltage ripple can be limited to ± 5%. So the small signal model of the converter at a duty cycle larger than 2/3 is established. Following the mathematical model, a single loop PID controller has been designed. Simulation results verify the correctness of the theoretical analysis. The system achieves lower output voltage ripple and fast dynamic response.