Development and test of a 30 kVA superconducting generator

A 3-phase, 30 kVA, 4 pole, 1800 rpm superconducting generator is built and tested. The field winding of the rotor is a racetrack type with NbTi superconducting wire. The rotor is composed of two dampers and a liquid helium container in which the field poles reside. The space between the outermost damper and the container is vacuum insulated. To continuously transfer the liquid helium from the stationary dewar into the rotor and return the helium gas conversely, a special coupling is installed. The stationary coupling is connected to the rotor through a ferrofluid seal. The open circuit characteristic (OCC) and short circuit characteristic (SCC) are obtained. Also, the test results under the light load (up to 3.6 kW) are given. From the design stage, 2-D FE analysis coupled with the external circuit has been performed. The external circuit includes the end winding resistance and reactance as well as two dampers. When compared with the test data, the FE analysis results show a very good agreement.