Outer Rotor Type Hybrid Stepping Motor

An outer rotor type hybrid stepping motor includes a stator, a rotor, a magnet disposed axially in the stator or the rotor, a stator core disposed inwardly from a gap between the stator and rotor, and a stator winding on the stator core. The rotor is disposed outside the gap. The magnet has an axial cross sectional area A. The residual magnetic flux density of the magnet is Br, and a total of magnetic fluxes exiting axially from the surface is AxBr. A gap average magnetic flux density, determined by dividing AxBr by the top cross sectional area small teeth poles on the rotor is Bg; pitch of the teeth is tau; and tooth width is Tw. Average magnetic flux density Bg, tooth pitch tau, and tooth width Tw are determined by the equation K=1/(pixBgxTw/tau), with the coefficient k in a range of 0.56-0.66 (1/T).