Operational Experience With the World's First 3600 rpm 4 MVA Generator at Siemens

HTS-excited synchronous machines provide substantial advantages with respect to efficiency, size, and operational behavior, with special focus on ship or off-shore applications. A 400 kW machine had been designed and built as technology demonstrator at Siemens to explore the feasibility of critical components and system interactions. After successful conclusion of these tests a first real-size machine was addressed: a 4 MVA HTS generator as core of a ship power generation system. This generator has been designed and manufactured and was subjected to extended testing in the Siemens A&D Large Drives systems test facility at Nuremburg, Germany. No problems were encountered caused by the high local centrifugal acceleration acting on rotor components, like e.g. the HTS windings. The cooling system was designed to provide power for cooldown, but also reliability and redundancy in operation, and performed as expected. The 6.6 kV air-cooled armature is an air-core winding made from Litz wire. The resulting machine characteristics were determined, the efficiency including rotor cooling system was measured and found to be about 2% superior to conventional generators of same power. Additional tests are going on, coupling the machine to a power converter and operating as a variable speed drive. In order to understand the frequency-dependant interactions detailed FE simulations were performed. This know-how aims to design an HTS machine as efficient inverter-driven motor, as one of the promising applications of synchronous HTS machines are high-torque propulsion motors for all-electric ships.