ELECTRIC MOTOR HAVING ROTOR CAPABLE OF CONFINING MAGNETIC FLUX

摘要

An electric motor comprising stator (20) having a plurality of annularly equispaced stator salient poles (24), four sets of permanent magnets (12a) disposed with an equal pitch and opposed to the inner peripheral sides of the salient poles (24), and a rotor (10) in which the permanent magnets (12a) are supported for rotation along the inner peripheries of the salient poles (24). The magnetic flux from the permanent magnets (12a) is allowed to flow through a rotor ring (Mp). An excitation controller (30) feeds the excitation coils (24b) for the salient poles (24) with an excitation current to synchronously drive the rotor (10). When the excitation coils (24b) are in the non-excited state, the rotor (10) is free to rotate substantially without load along the inner peripheries of the stator salient poles (24) by confinement of the magnetic flux; the startability is good.