抄録
As two-phase motors used for small fan drive and so on has zero torque point round one rotation, self-starting is serious problem. Therefore it is necessary to reduce torque ripple and to improve ability of self-starting by choosing the most suitable combination of cogging torque and electrical torque. But some reported analysis using Finite-Element-Method has a limit on separation between permeance distribution and flux distribution. Considering these problems, we developed a new method to analyze cogging torque using Schwarz-Christoffel transformation. We calculate effect of inter-pole shape, magnetization distribution of parmanent magnet and position of Hall-sensor, and the following conclusion is obtained:
(1) The inter-pole reduces ripple of permeance and cogging-torque.
(2) It is necessary to make the minimal shift of inter-pole from center position.
(3) By setting inter-pole gap equal or a little smaller than main teeth gap, total torque ripple can be reduced.
(4) Magnetizing permanent magnet into sinusoidal distribution reduces cogging torque effectively.
(5) Shifting the position of Hall-sensor against rotation direction improves ability of selfstarting.
