The effect of flux diverters on AC losses of a 10kVA high temperature superconducting demonstrator transformer

In this paper the design, construction and characterization of a 50Hz singl e phase High Temperature Superconducting (HTS) transformer is presented. Th e transformer is designed to deliver 10kVA at 77.4K and 20kVA at 65K. The t ransformer is made of two windings positioned at the middle limb of a three -limb iron core. The secondary winding is made of nine double pancake super conducting coils, using silver sheathed BPSCCO-2223 multifilamentary tapes with nominal critical current of 20A (at 77.4K and self field). The primary winding is made of copper to reduce the cost of HTS material. Utilizing a superinsulated non-metallic doughnut shaped cryostat with low background he at leak, the AC losses in the superconducting winding have been measured by calorimetric method. Two powdered iron flux diverters have been used insid e the cryostat at both ends of the superconducting winding in order to redu ce the radial component of leakage flux density in the HTS tapes. The use o f these flux diverters is shown to be very effective in reducing the AC los ses by 40% at the nominal current.