A synchronous reluctance type rotary electric machine includes a rotor and a stator. The rotor includes a shaft rotatably supported and extending in an axial direction with a rotation axis as a center, and a rotor core externally fitted and fixed to the shaft. The stator includes a stator core disposed around an outer circumference of the rotor core and spaced apart from the rotor core and having a plurality of teeth disposed at intervals in a circumferential direction and includes multipole multiphase armature windings respectively wound around the plurality of teeth.
Multi-layered hollow parts having a convex shape toward a radially inward side are formed for each pole in the rotor core. When the hollow parts are formed in this manner, a direction in which magnetic flux easily flows and a direction in which magnetic flux does not easily flow are formed in the rotor core. Thus, the synchronous reluctance type rotary electric machine rotates the shaft using a reluctance torque generated by the hollow parts.
Incidentally, at the time of starting a synchronous reluctance type rotary electric machine, it is necessary to detect a relative position between the stator core and the rotor core and to supply electric power to predetermined armature windings on the basis of the relative position. Therefore, an inverter is required to start the synchronous reluctance type rotary electric machine, which may increase the costs of the synchronous reluctance type rotary electric machine.
Thus, in order for the synchronous reluctance type rotary electric machine to be able to start without using an inverter, a so-called self-starting type synchronous reluctance type rotary electric machine in which a nonmagnetic conductor is provided in each of the hollow parts to generate an induced torque has been proposed.
Here, in order to reduce leakage magnetic flux at an outer circumferential portion of the rotor core, the hollow parts are formed as close as possible to the outer circumferential surface of the rotor core. Also, in order to fix the conductor to the hollow parts, a melted conductor is cast into the hollow parts in some cases. When the conductor is cast into a hollow part, the whole of the hollow part is filled with the conductor. In such a case, since magnetic flux pulsating according to a pitch of teeth of the stator links with the conductor, a harmonic current that does not contribute to rotation of the rotor flows through the conductor. Since the harmonic current is converted into Joule heat, there is a likelihood of the efficiency of the synchronous reluctance type rotary electric machine decreasing according to that amount.