A permanent magnet motor employing sets of divided magnets on the surface of the rotor enables stator current to be used to control the net flux in the stator teeth, yoke and airgap. Each set of divided magnets circumscribes a respective portion of an arc of 360.degree. about the center of the rotor and is made up of a subset of a number of successive south (S) magnet polarities and a subset of an of successive north (N) magnet polarities arranged such that each subset about the 360.degree. arc is of opposite polarity to the adjacent subset at either side. This enables terminal voltage to be kept constant as speed increases, but with less current than in the case of conventional surface magnet motors.

An electric motor including a stator having a stator core, a start winding and first and second main windings is described. The first main winding and the start winding are configured to form a lower number of poles than the second main windings. The stator core forms a stator bore. The motor also includes a rotor having a rotor shaft concentrically arranged axially of the stator core and a rotor core positioned concentrically with the rotor shaft. Secondary conductors are arranged axially of the rotor shaft and extend through the rotor core. A plurality of permanent magnets are located at an outer periphery of the rotor core and are magnetized to form a number of poles equal to the number of poles formed by the second main winding.

In producing a rotor for a rotating machine by bonding a rotor body and a plurality of permanent magnets to each other through a heating step and a subsequent cooling step, a rotor body having a larger coefficicient of linear thermal expansion at the cooling step has its joint surface formed by assembling of a plurality of small joint faces. Thus, it is possible to moderate a thermal stress in a brazing filler metal layer between the rotor body and each of the permanent magnets to avoid the generation of cracks in the permanent magnets having a smaller coefficient of linear thermal expansion at the cooling step and to firmly bond the rotor body and each of the permanent magnets to each other.

Permanent magnet housing spaces 3b and spaces 3c for flux barrier are formed within a rotor 3. A minimum value of a distance from a portion on a boundary face of the permanent magnet housing space in a rotor surface side which portion corresponds to an edge section of a permanent magnet 4 in its width direction to boundary faces of the both spaces in a rotation shaft side of the rotor 3 is determined to be greater than a distance of the permanent magnet housing space 3b in the thickness direction at an edge section of the permanent magnet 4 in its width direction, so that initial performance is maintained by preventing demagnetization of the permanent magnet due to a negative magnetic field from occurring. Thus a decrease in the cost of a brushless DC motor is realized by decreasing the volume of the permanent magnet.

In order to realize a permanent magnet dynamo electric machine which permits a high speed of rotation, the permanent magnet dynamo electric machine includes a stator 20 having a stator iron core 22 in which a stator winding 24 is wound, and a rotor 30 facing the inner circumference of the stator 20 and rotatably supported thereby, the rotor 30 having a rotor iron core 32 and a plurality of permanent magnets 36 arranged inside the rotor iron core 32 so as to face the stator iron core 22, wherein the rotor iron core 32 is provided with the same number of permanent magnet insertion holes 34 as the number of permanent magnets 36 for receiving the same at positions where the ratio R1/R0 is equal to or more than 0.85, wherein R0 is the radius of the rotor 30 and R1 is the radius of an imaginary circle drawn by inscribing the faces of the plurality of permanent magnets 36 at the side remote from the stator 20.