Electrical motor with bulk Y-Ba-Cu-O pellets

The interaction between a magnetic field and a superconducting (SC) bulk sample produces not only levitation forces but also transverse ones. They may be used in an electromagnetic coupling device to transmit a torque or in an electrical motor to produce a torque. The authors have designed and built a disk type motor (vertical axial gap) with a static three-phase armature resistive winding and a rotating part composed of eight YBaCuO pellets immersed in a liquid nitrogen vessel. The SC samples are melt textured using the top seed melt texturing method. The armature winding is fed by a power converter. Then the supplied frequency and the speed of rotation are variable. The motor was tested in different conditions and operated without magnetizing the SC samples. It works in a way as a variable reluctance motor even if the hysteresis behaviour of the SC pellets complicates the operation. Other experiments were carried out magnetizing the SC samples before their use as an inductor. The operation is close then to a permanent magnet motor. The experimental set up and the different tests are reported.