Thermal conductivity survey of different manufactured insulation systems of rectangular copper wires

Abstract

Especially in high power applications, thermal design of magnetic field coils is a critical partof efficient electromagnetic system design. Since thermal expansion of the coil effects magnetic fieldgeometry, temperature drop across the windings should be kept as low as possible. Here the insulationsystem between wires guides ohmic heat to the surface of the coil and influences the total thermalperformance. Because of very less information about the general thermal performance and quality ofmanufactured multilayer insulation systems, the present survey investigates several variants made ofenameled wires and Polyimide film wrapped wires. Hereby, different joining technologies like bondingor backfilling determine the thermal conductivity, which obviously differs from values of individual rawmaterials. Best performance could be gained with a Kapton®–CR film wrapped wire, backfilled withhigh thermal conductivity resin. Finally, the survey concludes that manufactured insulation systemsdrop approximately ten to twenty percent of the thermal conductivity, which could be theoreticallyachieved by an optimal layer composition of individual raw materials.