Compact centrifugal pump with magnetically suspended impeller

A pump apparatus comprising:

• a housing having inlet and outlet for respectively receiving and discharging fluid, and having a central axis;
• a rotor positioned within the interior of said housing to be rotatable about said central axis, said rotor having an impeller for pumping fluid between said inlet and said outlet, and being magnetically suspended to maintain a flow channel between said rotor and said housing;
• an electric motor adapted to drive said rotor about a rotational axis substantially coincident with said central axis, said electric motor comprising a motor rotor assembly disposed within said rotor and a motor stator assembly disposed within said housing;
• a magnetic suspension device comprising:
• an annular rotor primary pole piece mounted within said rotor coaxially with said rotational axis, the annular rotor primary pole piece comprising a ferromagnetic material for channeling magnetic flux and having a first end surface, a second end surface, and a cylindrical side surface configured to serve as a rotor pole face;
• a plurality of electromagnet units mounted within said housing and circumferentially distributed at regular intervals about said central axis, each electromagnet unit comprising:
• a pole shoe having a first end surface, a second end surface, and a side cylindrical surface configured to serve as a casing pole face;
• an iron core extending from said pole shoe;
• a back yoke connecting two or more said iron cores of different electromagnet units together;
• and
• a coil wound around said iron core for conducting electric current;
• wherein said pole shoe, iron core, and back yoke comprise ferromagnetic material for channeling magnetic flux;
• wherein the first end surface of said rotor primary pole piece and the first end surfaces of all said pole shoes are on a same side along an axial direction;
• wherein said rotor pole face and each said casing pole face oppose to each other and define a primary suspension gap thereinbetween, said primary suspension gaps being axially aligned with each other and circumferentially separated from each other;
• at least one permanent magnet generating a plurality of bias magnetic fluxes, each said bias magnetic flux radially passing through one said primary suspension gap, and passing through the interior of said rotor primary pole piece and of said pole shoe of electromagnet unit;
• wherein said at least one permanent magnet is magnetized in such a direction that all said bias magnetic fluxes pass through said primary suspension gaps in a same polar direction;
• a plurality of position sensors disposed circumferentially around said rotor and mounted within said housing for detecting a radial position of said rotor pole face;
• a feedback control system for generating and delivering electric current into said coils of said plurality of electromagnet units according to a real-time output of said position sensors;
• wherein said feedback control system comprises a control strategy adapted to achieve stability of radial positioning of said rotor;
• wherein the plurality of said electromagnet units are electrically and magnetically connected to jointly generate a modulating magnetic flux for active control of the position of said rotor along any one of two orthogonal radial axes, a first radial axis having a first side and a second side divided by a second radial axis, said modulating magnetic flux radially passing through a plurality of said primary suspension gaps and superimposing said bias magnetic fluxes to enhances the bias magnetic flux in the primary suspension gap located on the first side of said radial axis, and weakens the bias magnetic flux in the primary suspension gap located on the second side of said radial axis.