High Temperature Active Magnetic Bearings in Industrial Steam Turbines

After 8 years of industrial research and development between industry and Zittau/Görlitz University, the prototype of a feed water power turbine (SPAT) with active magnetic bearings was successfully taken in operation at the Jänschwalde power plant in 2015. Due to extended conditions of use (particularly high process and environmental temperatures) the active magnetic bearings in the turbo machines must be cooled elaborately. In conventionally supported turbo machines the lubri- cant in the friction bearings additionally does the cooling. Parts of the heat flux are dissipated from the bearing by the bearing oil. In terms of turbo machines with magnetic bearings lubricant is not used. This leads to significantly higher temperatures in the area of rotor lamination and its sleeves. Particularly demanding is the cooling of the sleeves which is currently very demanding – compressors are necessary. The tube cooling applied reduces the effi- ciency of the magnetic bearing which is high compared with hydrostatic friction bearing. Moreover, the additional peripheral effort has a negative effect for investment and maintenance in cost accounting. This paper shows the stages in developing High Temperature Magnetic Bearings (HTAMB). First approaches of suitable HTAMB concepts are depicted. Within the next 3 years shall on the basis of theoretical and experimental investigations be determined which state of the art materials and construction principles must be used and applied. The focus within that topic is the use of temperature resistant materials for the lamination of active radial magnetic bearings with respect to elimination of high manufacturing effort of sleeve cooling. For this reason the essential tests of magnetic and catcher bearing components shall be realized at the test rig for magnetic and catcher bearings MFLP. Single effects and long-term strain will be analyzed under scaled power plant conditions. The test field is introduced by representing its main parameters.