Michael Dr. Frank

380 kW synchronous machine with HTS rotor windings--development at Siemens and first test results

Applying HTS conductors in the rotor of synchronous machines allows the design of future motors or generators that are lighter, more compact and feature an improved coefficient of performance. To address these goals a project collaboration was installed within Siemens, including Automation & Drives, Large Drives as a leading supplier of electrical machines, Corporate Technology as a competence center for superconducting technology, and other partners. The main task of the project was to demonstrate the feasibility of basic concepts. The rotor was built from racetrack coils of Bi-2223 HTS tape conductor, these were assembled on a core and fixed by a bandage of glass-fibre composite. Rotor coil cooling is performed by thermal conduction, one end of the motor shaft is hollow to give access for the cooling system. Two cooling systems were designed and operated successfully: firstly an open circuit using cold gaseous helium from a storage vessel, but also a closed circuit system based on a cryogenerator. To take advantage of the increased rotor induction levels the stator winding was designed as an air gap winding. This was manufactured and fitted in a standard motor housing. After assembling of the whole system in a test facility with a DC machine load experiments have been started to prove the validity of our design, including operation with both cooling systems and driving the stator from the grid as well as by a power inverter.

High-Temperature Superconducting Rotating Machines for Ship Applications

Main applications for rotating electric synchronous machines are given as generators and motors; a small niche can also be found in synchronous condenser-applications. High temperature superconducting (HTS) rotating machines show several significant advantages over machines built in conventional techniques. These are mainly increased efficiency, higher power density, and enhanced electrical stability. Especially for on-board applications, these properties may be decisive to save fuel and space and improve the capabilities. In the past, basic programs were carried out to demonstrate in principle the possibility to build such machines. Meanwhile these programs have shown great success and the feasibility of HTS machines for such applications has come into reach. For that reason developments for HTS machines in the megawatt-range are now being in progress, for propulsion purposes as well as for power generation applications. Started with the built of a 400 kW model motor that has operated successfully for more than two years, Siemens is now being engaged in the development of HTS machines for all electric ship application in the megawatt-range. A demonstrator for a 3600 rpm 4 MVA generator has been set up in the Nuremberg test facility for extended type and system testing. Results of tests with both machines will be presented. Technical implications of this new technology for ship-borne application will be discussed together with general economic assessments

Advances in and prospects for development of high-temperature superconductor rotating machines at Siemens

We report on the successful manufacture and testing of the Siemens 400 kVA HTS synchronous motor, which has been in operation for over 3 years, and on the progress of the 4 MVA synchronous motor/generator, which has been manufactured and is now in a phase of extended testing. Furthermore, the benefits of HTS machines will be discussed with emphasis on applications in ships. The development of future marketable products will be strongly dependent on the progress of secondary technologies, such as wire performance and efficient cost-effective refrigerators.

Thermosyphon Cooling System for the Siemens 400kW HTS Synchronous Machine

A commercial GM cryocooler is employed to cool the rotor of the first Siemens 400 kW HTS machine. Excellent thermal connection between cold head and rotor is achieved using a thermosyphon. At the rotor’s inner surface the required cooling power is provided by evaporating fluid, that is recondensed at the coldhead. Our configuration allows an easy mechanical decoupling of the stationary cold head and the rotor, using a magnetic liquid rotary seal. In order to shorten cool‐down time, a precool to 70 K is done with a thermosyphon filling of nitrogen, while a motor operating temperature of 25 K is reached using neon. Temperature difference between the thermosyphon’s cold and warm ends is below 1 K for a heat transfer of 40 W. During operation, a temperature controller stabilizes condenser temperature and hence rotor temperature. The self‐regulating cooling system has been operated continuously and without problems since Spring 2001. The machine was also operated with newly developed pulse‐tube cryocoolers, th...