Tatsuo Horii

Magnetometric Demagnetizing Factors for Various Shapes of Rotational Symmetry

We have investigated the magnetometric demagnetizing factors of rotation-symmetrical magnetic bodies of relative permeability mu placed in a uniform magnetic field parallel to the axis of rotation. The bodies we considered include a cylinder, a sphere, a bicone, and a rotating astroid. We numerically calculated the magnetometric demagnetizing factors from the surface magnetic charge densities sigma obtained by the surface magnetic charge simulation method. We show that the magnetometric demagnetizing factors for various shapes of rotation-symmetrical bodies are significantly different from those of a sphere. We have determined the shape producing the largest demagnetizing field in ferromagnetic bodies with sufficiently large relative permeability mu . We report the magnetometric demagnetizing factors for uniformly magnetized bodies (mu = 1 , i.e., susceptibility chi = 0 ) of various shapes.

Characteristics of a hybrid type 3‐phase stepping motor

Among hybrid type (HB type) stepping motors, the 2-phase type is widely used, as is the 5-phase type for high-resolution purposes. On the other hand, the 3-phase type is considered to be superior to other types from the viewpoint of cost performance. However, no study has been made of 3-phase HB type stepping motors. In this paper, the performance characteristics of an HB type 3-phase stepping motor are analyzed, and, further, the influence of motor structure and of excitation modes on the motor performance are also investigated. As a result, the relationship between number of stator main poles and number of rotor teeth is formulated. Torque versus angle characteristics, step response characteristics, and pullout torque characteristics are clarified under the various excitation modes in Y- and Δ-winding connections.