Design And Analysis Of DC Disconnector For ITER Converter

ITER is a large-scale tokamak under construction. The DC Disconnector is animportant electrical equipment to isolate the power supply and the superconductingcoil for the ITER PF converters. According to the design requirements, thedisconnector operates under55kA rated current and350kA/1s peak current, and thewithstand voltage to ground is20kV. As it cannot be purchased in the market, thedesign study of the DC disconnector under the input parameter requirements will befinished in this thesis.A DC disconnector which is drove by motor to compress multi-piecesrectangular conductors with large aluminum buses has been designed in this study.Multiple physical field analyses have been done on the disconnector by ANSYSsoftware. The simulations including steady-state thermal analysis under rated current,dynamic stability analysis under short-circuit current, electric field analysis of theinsulation parts and mechanical analysis of the transmission parts. The simulationresults show that the temperature rise, isolation level of the disconnector meets thedesign requirements, the disconnector transmission parts have enough mechanicalstrength to provide suitable contact pressure. On the basis of simulation analyses,improvement for the design is suggested specifically.To assess the design of the DC disconnector, contact pressure test, dynamicstability test and temperature rise test are carried. In the contact pressure test, suitablecontact pressure is provided, though the contact pressure of electrical contacts is notquite even. In the dynamic stability test, the disconnector terminals receives thehorizontal electrodynamic force tension; although electric contacts are worn a little,the disconnector can withstand the impact of short-circuit current350kA/1s. In thetemperature rise test, the contact temperature below the limit temperature rise65°C,and the uneven contact pressure leads to the situation which contact temperature ofseveral contacts is a bit higher. Increasing the contact pressure and reduce the gapbetween the rectangular conductors can improve it.To improve the current capacity of the electric contact, optimization design ofthe electric contact is studied. Multi-spot contact structure has been designed.Temperature rise analyses of multi-spot contact under rated and transient currents areperformed. The simulation results show that multi-spot contact has lower temperaturerise than singe contact under relative high force. The test platform has been designedspecifically for electric contact of DC disconnector. The experiment results show that the contact resistance of the multiple electrical contacts at a certain contact pressure issmaller than the single electrical contact, but the contact resistance is unstable. Inpractical applications of the multiple electrical contacts, larger contact pressure shouldbe applied with respect to the single electrical contact to ensure the contact resistancestability.The DC disconnector that has been designed in this study meets the requirementsfor the ITER PF converters, and it has already passed the Preliminary Design Revieworganized by ITER. The test platform for electric contact of DC disconnector providea basis for further study of the factors affecting the contact resistance of the DCdisconnector electric contact.