Induction motor driven seal-less pump

Abstract

A seal-less pump and electric motor assembly includes a motor rotor fixed to a driving shaft connected to an impeller in the pump assembly. The rotor and impeller are enclosed in a common housing such that the rotor rotates within any fluid being pumped by the impeller. The portion of the housing circumscribing the rotor includes a plurality of axially extending, circumferentially spaced strips of magnetic material penetrating through plastic material of the housing. Each of the strips coincide with corresponding ones of the pole teeth of a motor stator circumscribing the outer portion of the housing such that the strips in the housing act as extensions of the pole teeth. In one embodiment, the strips of magnetic material in the housing are formed by molding powdered iron in a plastic binder material. The strips are then placed in a mold in which the housing is formed by injecting plastic. The plastic binder in the strips melds with the injected plastic to form a continuous housing for enclosing the rotor. The ferromagnetic material strips extend through the housing and are spaced from the rotor surface by a normal air gap distance so as to improve the efficiency of the motor by having the magnetic strip act as extensions of the motor stator pole teeth. In one embodiment, the rotor includes a shaft, a core including a molded magnetic powder and plastic composite material surrounding the shaft, and an annular corrosion resistant electrically conductive tube surrounding the core.