Short Circuit Tests on a Coreless HTS Synchronous Generator

• Published in: IEEE transactions on applied superconductivity 2013-06, Vol.23 (3), p.5201505-5201505
• Main Authors: Bailey, W. O. S., Yang, Y., Beduz, C., Goddard, K. F.
• Format: Article
• Language: English
• Subjects: Air-core rotors; Applied sciences; Circuit properties; Coils; Connection and protection apparatus; Electric relays; Electric, optical and optoelectronic circuits; Electrical engineering. Electrical power engineering; Electrical machines; Electronic circuits; Electronics; Exact sciences and technology; Generators; High temperature superconductors; High voltage or high current generators; high-temperature superconducting (HTS) machines; Kinetic energy; Miscellaneous; Rotors; Short circuits; Stator cores; Stator windings; Stators; superconducting winding; Superconductivity; Surges; Switching, multiplexing, switched capacity circuits; synchronous machines; Various equipment and components; Windings
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/TASC.2013.2244196

A series of short circuit tests have been performed on a coreless (air-core) high-temperature superconducting (HTS) rotor, installed inside a conventional stator. The machine was driven like a generator using an 11 kW drive motor, to a maximum frequency of 20 Hz. The short circuit was activated at the stator terminals using a three-phase contactor switch and a remote trigger. Tests were conducted with a range of values for each of the following parameters: i) initial frequency, between 4 and 20 Hz; ii) operating field current, between 5 and 80 A; and iii) external resistance, between 14 and 160 mΩ. For each investigation, the other parameters were fixed. Large current surges were observed in both the stator (3 times its nominal current) and in the rotor (1/4 of the initial operating current). Some localized thermal measurements of a coil in the HTS winding were also recorded but, during the transient events, these measurements are invalidated by inductive voltages. The temperature is believed to remain steady during the short circuit event. The rotational kinetic energy of this rotor was almost half of its counterpart, but it was the power supply and the series resistor that absorbed most of the magnetomotive energy after the short-circuit. These components are essential parts of the HTS generators' overall system and their operating limits must also be considered in new designs.