| ITER poloidal field (PF) coils play an essential role in the plasma formation stage, ohmic heating and the plasma shape and position control, whose reliability and stability means a lot to the safe operation of the entire tokomak device. Four-quadrant 12-pulse rectifier operation mode is adopted by PF coil power supply system to realize the output of rated DC ±55 kA with two converter units in parallel. As the main inductive device of the power system, circulating reactors play an importance role in balancing output voltage of two bridges in parallel, realizing circulating mode when current crosses zero smoothly and restraining magnitude and rise rate of short-circuit current. According to the requirements of supply system, the reactor should operate safely under steady 27.5 kA and short 190 kA. Due to the requirements of high power and dynamic stability under large current, there are no corresponding products in the market. Thus, research on a new structure and its reliability means a lot to the PF supply system, which can also provide reference to the design of similar coils.The operation mode and fault mode are studied to get the electrical parameters requirements of the reactor. Based on the combination of high-current inductor structural characteristics, a new structure of dry-type air-core water-cooling reactor with epoxy resin casting technique is presented. The structure has the advantages of a constant inductance, high structural strength, low noise operation, and simple installation and maintenance.The inductance-frequency property of conductor with large cross-section is studied. For DC inductance calculations, the characteristics and conditions of induction coefficient method, row mutual inductance method and finite element method (FEM) are summarized by the design of the circulating reactor. For the effect of skin effect and proximity effect on the AC inductance and resistance, the comparison of partial element equivalent circuit (PEEC), finite element method (FEM) and measurement data of prototype demonstrates the high accuracy of the methods.Multi-physics coupling analysis is studied, which is applied to analyze the dynamic stability and thermal stability of reactor. Firstly, based on electromagnetic analysis, the magnetic field distribution and electromagnetic load of coil are studied, which shows that the coils expand in radial direction and shrink in axial direction. Secondly, based on electromagnetic-structural coupling analysis, the forces of coils at different modes are studied. Thirdly, based on response spectrum method, the anti-seismic property of reactor under seismic level 2 with damping ratio 4% are discussed. Fourthly, based on electromagnetic-fluid-temperature coupling analysis, the distribution of winding temperature and water pressure drop are analyzed and the cooling water system is determinated. At last, based on the electromagnetic-temperature coupling analysis, the effect of contact resistance on the aluminum busbar heating and the eddy current heating of high magnetic material nearby the reactor are analyzed.The manufacturing process and test of reactor are studied. The processes to guarantee the consistency and the quality of coils are presented. In addition, the test regulation and acceptance criteria are formulated. Finally, the tests, such as inductance and resistance test, interturn insulation test, withstand voltage test, temperature rise test, short-circuit fault current test and integration testing test and so on are introduced in detail. The measurements show that the proposed structure can totally meet the requirements of supply system, which further demonstrates the high reliability of the promoted design. |
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