Reactive compensation of long primary HTS-linear synchronous machines

In propulsion systems requiring high speed and high acceleration, the long primary high-temperature superconducting linear synchronous machine (HTS-LSM) is a competitive candidate, since it can provide steady and high thrust. However, the armature windings on the long primary uncovered by a mover with HTS magnets can cause large flux leakage, which can lead to a high armature reaction voltage and a poor power factor. In this paper, to restrain the armature reaction voltage of the long primary HTS-LSM, compensation windings are proposed for installation on the primary. First, a mathematical model of a five-phase four-pole long primary HTS-LSM is established, and it is determined that the high armature reaction voltage is caused by the large self-inductance of uncovered armature windings. Then, compensation winding is applied in the armature winding to reduce the equivalent self-inductance. Four different compensation winding installation positions are studied and compared. To prevent the current in the compensation windings from affecting the function of the HTS-racetrack magnet on the mover, a switch control strategy for the compensation windings is proposed. Finally, prototypes of armature windings with compensation windings are manufactured and the effectiveness of the compensation windings are validated and compared.