Performance of high temperature superconducting coils for implementation into megawatt class generators

The United States Air Force and Ballistic Missile Defense Organization are developing a 1 MW exciter/generator for airborne applications. The exciter is constructed with an eight-pole external field winding and rotating hydrogen cooled armature with integral rectifier. The exciter was originally designed with high purity aluminum field coils cooled with liquid hydrogen. The United States Air Force is presently investigating the potential for replacing the aluminum field coils with high temperature superconductor (HTS) field coils cooled with hydrogen. Eight HTS racetrack-shaped field coils were built with BSCCO-2223 tapes for operation at 20 K. They were constructed to be consistent in geometry with the aluminum coils. The electrical performance of the HTS coils exceeded the required 72000 ampere-turns at the 1-/spl mu/V per cm electric field criteria. This paper reviews the design, construction and testing of the field coils and discusses the potential of this technology for airborne applications.