Experimental estimation of a 5-axis active control type bearingless canned motor pump

Bearingless motors are characterized by integration of electrical motors and magnetic bearings. These motors can realize magnetic suspension of rotor shafts without mechanical contacts. If the bearingless motor is applied to a canned motor pump, it is possible to levitate and rotate a impeller and a rotor shaft of a centrifugal pump. Therefore, the bearingless canned motor pump can realize next several advantages; (1) high power and high head, (2) clean liquid sending, (3) maintenance free, (4) longer operating life, (5) high chemical resistance. On the other hand, the rotor shaft and the stator must be covered with thick bulkheads, because fluid flows into the gap between the rotor shaft and the stator. It becomes difficult to generate sufficient suspension force for magnetic suspension, as a magnetic gap length is increased by the thick bulkheads. Accordingly, a novel structure of a 5-axis active control type bearingless motor, that can generate the sufficient suspension force under the wide-gap condition, has been proposed. This paper introduces pump characteristics with experiments using a prototype of the proposed novel structure.