Compact centrifugal pump with magnetically suspended impeller

A pump apparatus, comprising:

• a housing having a central axis and an inlet and an outlet adapted to respectively receive and discharge fluid;
• a rotor magnetically suspended in the housing and rotatable about the central axis, the rotor having an impeller adapted to pump fluid;
• a motor adapted to drive the rotor about a rotational axis substantially coincident with the central axis;
• a magnetic suspension device including:
• an annular rotor primary pole piece disposed in the rotor coaxially with the rotational axis, the annular rotor primary pole piece including a ferromagnetic material adapted to channel magnetic flux and having first and second end surfaces and a cylindrical side surface adapted to serve as a rotor pole face;
• electromagnet units disposed in the housing and circumferentially distributed about the central axis, each electromagnet unit including:
• a pole shoe having first and second pole shoe end surfaces and a side pole shoe cylindrical surface adapted to serve as a casing pole face;
• a core extending from the pole shoe;
• a back yoke connecting the cores of different electromagnet units together;
• and
• a coil wound around the core and adapted to conduct electric current;
• wherein the pole shoe, the core, and the back yoke each includes ferromagnetic material adapted to channel magnetic flux;
• wherein the first end surface of the rotor primary pole piece and the first end pole shoe surfaces of the pole shoes are on a first side along an axial direction;
• wherein the rotor pole face and each of the casing pole faces oppose each other and define a primary suspension gap thereinbetween, the primary suspension gaps are axially aligned with each other and circumferentially separated from each other;
• a permanent magnet adapted to generate bias magnetic fluxes, each of the bias magnetic fluxes radially passing through one of the primary suspension gaps, and passing through the rotor primary pole piece and pole shoe of the electromagnet unit;
• wherein the permanent magnet is magnetized in such a direction that all the bias magnetic fluxes pass through the primary suspension gaps in a same polar direction;
• wherein the electromagnet units are electrically and magnetically coupled to jointly generate a modulating magnetic flux for active control of a position of the rotor along either one of two orthogonal radial axes, a first radial axis having a first side and a second side divided by a second radial axis, the modulating magnetic flux radially passing through a plurality of the primary suspension gaps and superimposing the bias magnetic fluxes to enhance the bias magnetic flux in the primary suspension gap on the first side of the radial axis, and weaken the bias magnetic flux in the primary suspension gap on the second side of the radial axis.