Operational characteristics of linear synchronous actuator with field-cooled YBCO bulk secondary

It is expected that electric devices would be high efficiency, high output and downsized by using high-temperature superconducting (HTS) bulk materials. In the previous study, we have fabricated and tested a linear synchronous actuator with double-sided primary and YBCO bulk secondary; the linear actuator consists of a field-cooled YBCO bulk for secondary (mover) and copper windings with an iron core as a primary. The primary, which was excited by a three-phase VVVF (variable voltage variable frequency) power source to generate sinusoidal traveling magnetic fields, was divided into two sections: 1) the starting section in which the secondary is accelerated as an induction machine; and 2) the synchronous section in which the secondary moves with a specified synchronous speed. And we have evaluated both of the static and dynamic characteristics on this linear synchronous actuator. However, for practical use of linear actuator with field-cooled HTS bulk secondary, it is required to examine the distribution of magnetic field within the HTS bulk which is exposed to the traveling magnetic field in a realistic operational environment of linear actuator. Therefore, in this study, we repeated the mode of acceleration, constant-speed, deceleration and stop with the control circuit in the synchronous section. The direction of the mover can be turned automatically by the switching device and it made round-trip running possible. Then, we carried out many times round-trip operations and evaluated the change of the magnetic field on the surface of the YBCO bulk in various conditions with trapped field of the secondary and traveling magnetic field generated by the primary windings.