SuperPower’s Second Generation HTS Conductor Design for Stability and Low AC Losses

SuperPower is developing a conductor design for improved mechanical properties, quench stability, and low ac losses. Coated conductors are typically 12 mm wide with a few microns of silver overlayer. SuperPower's design modifies such base conductor designs into geometries more suited for practical applications. Wide conductors are slit into 4 mm wide tapes, in particular for cable applications, but also to reduce ac losses. After slitting, the conductor is stabilized with approximately 20 microns of surround copper stabilizer, completely encapsulating the conductor and providing a hermetic seal. Other advantages of the surround copper stabilizer configuration are rounded edges for dielectric integration and superior over-current handling capability (9X critical current with 300 ms wide pulses). Prototype 1 in cables made by Sumitomo Electric using this practical conductor showed total ac losses under 0.4 W/kA-m. To further reduce ac losses, especially for high frequency applications of the military, SuperPower's conductor design involves striating the current-carrying layers by a photolithography process. Several racetrack coils made with our practical coated conductors have been provided to Rockwell Automation for use in a demonstration motor. Recent results of our practical coated conductor will be discussed.