Locked Rotor and Transient Tests of a 100 kW HTS Machine

Locked rotor and “short circuit at the stator terminals” are two standard motor tests that provide operators with useful data about the electro-mechanical performance of rotating machines for installation. A programme of motor tests was performed on a novel machine with an HTS rotor winding and a conventional copper wound stator. The rotor winding was cooled down to 77 K. The differences when driving 0 and 190 A in the stator winding whilst ramping the field current in the locked rotor close to its critical current are discussed by interpreting small changes in the voltages measured at different locations in the winding. The perpendicular field generated by the stator produced the greatest impact on the HTS winding and its starting torque. Finally, a comparison of single-phase short circuits with three-phase short circuits unveiled a doubling in the peak stator current induced and the period for the transient to dissipate, but a moderate reduction in the peak (spiking) current in the HTS winding.