Thermal Dissipation Modelling and Design of ITER PF Converter Alternating Current Busbar

Abstract

Because the larger metallic surrounds are heated by the eddy current, which is generated by the AC current flowing through the AC busbar in the International Thermonuclear Experimental Reactor (ITER) poloidal field (PF) converter system, shielding of the AC busbar is required to decrease the temperature rise of the surrounds to satisfy the design requirement. Three special types of AC busbar with natural cooling, air cooling and water cooling busbar structure have been proposed and investigated in this paper. For each cooling scheme, a 3D finite model based on the proposed structure has been developed to perform the electromagnetic and thermal analysis to predict their operation behavior. Comparing the analysis results of the three different cooling patterns, water cooling has more advantages than the other patterns and it is selected to be the thermal dissipation pattern for the AC busbar of ITER PF converter unit. The approach to qualify the suitable cooling scheme in this paper can be provided as a reference on the thermal dissipation design of AC busbar in the converter system.

Preliminary design of high power magnet converter for CRAFT

“…Each thyristor has an external series fast fuse for short circuit protection and an external paralleled snubber for overvoltage protection. The thyristor, fast fuse and snubber are the key devices of the converter that parameters and types are needed to be determined [12][13][14]. According to the design requirements, the thyristor junction temperature must be lower than 125 °C and the thyristor thermal accumulation is lower than the allowable value during the downstream short circuit of DC reactor, the fast fuse must be melted during the bridge short circuit and must not be melt during the downstream short circuit of the DC reactor, the snubber consisting of resistor and capacitor is needed to reduce the commutation over-voltage to be lower than half max repetitive peak forward voltage of thyristor.…”