Electrical Performance of Slow Response Excitation Type Superconducting Generator

Abstract

Superconducting generators have many advantages such as increasing generation efficiency, improving power system stability and reducing size and weight in comparison with conventional generators. In Japan, 70MW class superconducting generators (model machine) are being developed. Manufacture of “70MW class slow response excitation type rotor” started in 1992 and factory tests were conducted in 1996. Succeeding to the factory tests, the rotor was combined to the stator with air gap windings in the verification test facility (in Osaka power station) and verification tests were conducted in 1998. Satisfactory results which represent the advantages and the reliability of superconducting generators were obtained.
In this paper, test results of electrical characteristics of 70MW model generator such as “electrical constants” and “No load open/short circuit characteristics” are discussed. Evaluation by 3D magnetic analysis are also described. The main results are summarized below.
•The synchronouce reactance (X_d) was 0.42 p. u. which is 1/4_??_1/5 of conventional generators. X_d can be analyzed precisely by 3D magnetic field analysis which is now taken into account for the effect of the armature end windings on electrical characteristics.
•X_d''' which is originated in “double layer damper system” was separated clearly from 3-phase sudden short circuit test.
These reactances can be analyzed by quasi-3D analysis considering the boundary condition of rotor surface.
•By means of these magnetic analyses, fundamental design methods considering the end windings were established. These are applicable to the design of “200MW class pilot superconducting generator”.