Abstract: A squirrel-cage induction motor comprises a stator having a stator core and stator windings divided into first and second coils with different numbers of poles, and a squirrel-cage rotor including a rotor core and a plurality of rotor conductors embedded in the vicinity of the surface of the core. The number of the rotor conductors is the same as the average number of poles of the first and second stator coils, which conductors are arranged equidistantly along the periphery. This induction motor, with the construction of a squirrel-cage rotor, permits a variable speed operation without using any special device.

Abstract: A variable speed rotary electric machine comprises a stator composed of a stator core and first and second stator windings wound on the stator core, and a cage rotor mounted rotatably within the stator and composed of a rotor core and rotor conductor disposed in a squirrel-cage configuration. The first stator winding is connected to an AC power supply of a fixed frequency. The second stator winding is connected to a power supply of a variable frequency. The first and second stator windings are so wound as to form, respectively, numbers of poles differing from each other. The rotor conductors of the cage rotor are electromagnetically coupled with the magnetic flux generated by the first and second stator windings, respectively, and so disposed as to form a number of poles which is intermediate between the number of the poles formed by the first stator winding and the number of poles formed by said second stator winding.

Abstract: A cooling system for a rotary electric machine having a stator including a stator core and a stator frame for supporting the stator core and a rotor including a yoke, a plurality of salient magnetic poles mounted on the periphery of the yoke and shield plates bridging the tips of the adjacent magnetic poles wherein the cooling system comprises groups of air-discharging and air-charging ducts radially penetrating the stator core, each group of the ducts being axially aligned with a predetermined distance from each other and air-discharging windows formed in the shield plates at predetermined axial positions thereof, and the axial area of each group of the air-discharging ducts is larger than the axial area of the air-discharging window of the corresponding shield plate thereby increasing the flow rate of the cooling air through the rotary machine.