Circulation fan apparatus and circulation-fan driving motor

A circulation fan apparatus including

• a hermetic vessel (1) containing a corrosive process gas therein and
• a circulation fan (2) installed in said hermetic vessel for circulating said corrosive gas within said hermetic vessel, rotors (2-1, 2-2) of said circulation fan are rotatably supported by bearings, wherein
• said bearings comprise radial magnetic bearings (4, 5) and at least one axial magnetic bearing (6, 7), said radial magnetic bearings are disposed on opposite sides of said circulation fan,
• displacement sensor targets (4-1, 5-1, 6-1, 7-1) and rotor-side magnetic poles (4-2, 5-2, 6-2, 7-2) of said radial magnetic bearings (4, 5) and axial magnetic bearings (6, 7) are fixed to the rotors (2-1, 2-2) of said circulation fan (2) and are disposed in a hermetic space communicating with said hermetic vessel, and
• displacement sensors (4-3, 5-3, 6-3, 7-3) and stator-side magnetic poles (4-4, 5-4, 6-4, 7-4) opposing said displacement sensor targets and rotor-side magnetic poles are disposed outside of said hermetic vessel with cans or protection layer (14, 15, 17, 18) being interposed between the displacement sensors and the stator-side magnetic poles and the displacement sensor targets and rotor-side magnetic poles,
• wherein said displacement sensors (4-3, 5-3, 6-3, 7-3) are disposed adjacent to said stator-side magnetic poles (4-4, 5-4, 6-4, 7-4), respectively.