Abstract: In a permanent magnet commutator type D.C. servomotor having a wound iron core armature and a permanent magnet stator, the stator includes a uniquely formed annular yoke. The unique yoke includes a central opening and a plurality of permanent magnet pole pieces, which are securely held to arcuate magnetic material projecting into the opening and which are spaced equally from and about the axis of the yoke. The magnets and arcuate magnetic material form boundaries to accommodate the armature and also form a relieved area between the magnets designed for reduced field distortion. The radial thickness of the magnet pole pieces, the arcuate members of magnetic material and the radial thickness of the yoke are proportioned relative to each other and to the I.D. of the pole pieces at prescribed values to maximize the motor performance.

Abstract: In an electric motor of the type having a permanent magnet rotor which is subject to cogging torque, a plurality of skewed reluctance notches are cut in the outer diameter of the rotor laminations. The rotor laminations have first and second sets of axial openings which are filled respectively with rare earth magnet material and non-ferrous casting material.