Mechanical and electric characteristics of vacuum impregnated no-insulation HTS coil

• A single pancake no-insulation coil was fabricated with a brass lamination conductor.
• Charging/discharging test was performed using liquid nitrogen and conduction-cooling.
• Consistent contact resistance was verified after epoxy impregnation.
• Equivalent circuit was used to estimate the heat generation during charging operation.
• The HTS coil did not showed delamination problem for the conduction cooling.

For the conduction cooling application, epoxy impregnation is inevitable to enhance the thermal conduction. However, there have been several research results on the delamination problem with coated conductor and the main cause of the delamination is related with the different thermal contraction between epoxy, the insulation layer and the weak conductor. To avoid this problem, the amount of epoxy and insulation layer between conductors should be minimized or removed. Therefore, no insulation (NI) winding method and impregnation after dry winding can be considered to solve the problem. The NI coil winding method is very attractive due to high mechanical/thermal stability for the special purpose of DC magnets by removing the insulation layer. In this paper, the NI coil winding method and vacuum impregnation are applied to a HTS coil to avoid the delamination problem and enhance the mechanical/thermal stability for the conduction cooling application. Through the charging/discharging operation, electric/thermal characteristics are investigated at 77 K and 30 K.