Squirrel-cage rotor with shaped-conductor harmonic reduction

A squirrel-cage rotor comprising:

• a) a rotor for use in a motor of the slotted stator core type core comprising one or a plurality of first units of steel sheets and one or a plurality of second units of steel sheets, each unit being composed of a plurality of steel sheets each having a number of slot-forming punched portions for forming slots, the number of which differs from the number of slots of a stator core, each punched portion including a main portion and an additional portion extended from the main portion toward the outer circumference of the rotor and inclined in the direction of either one of two sides along the circumference of the rotor relative to the position of the main portion such that each punched portion has an unsymmetrical configuration, each main portion having the center deviated from a distal end of each additional portion by a distance d satisfying the following expression (A) circumferentially of the rotor:
• ##EQU32## where D=rotor diameter
• z=the number of stator slots
• p=the number of pole pairs
• each first unit being composed of the steel sheets laminated so that the respective additional portions are inclined in the direction of the one side along the circumference of the rotor relative to the positions of the respective main portions and so that the main portions are piled one upon another, each second unit being composed of the steel sheets laminated so that the respective additional portions are inclined in the direction of the other side along the circumference of the rotor relative to the positions of the respective main portions and so that the main portions are piled one upon another;
• b) projections formed on each steel sheet so as to be extruded or cut and raised by way of stamping, the projections of each steel sheet being engaged with the projections of the adjacent steel sheet when the steel sheets are laminated;
• c) rotor bars embedded in slots of the rotor formed by the punched portions of the steel sheets laminated, respectively;
• and
• d) end rings provided for short-circuiting the rotor bars at both ends of the rotor core, respectively.

A squirrel-cage rotor for use in a motor of the slotted stator core type comprising:

• a) a rotor core comprising one or a plurality of first units of steel sheets and one or a plurality of second units of steel sheets, the units being stacked with a gap between each unit and the adjacent unit, each unit being composed of a plurality of steel sheets each having a number of slot-forming punched portions for forming slots, the number of which differs from the number of slots of a stator core, each punched portion including a main portion and an additional portion extended from the main portion toward the outer circumference of the rotor and inclined in the direction of either one of two sides along the circumference of the rotor relative to the position of the main portion such that each punched portion has an unsymmetrical configuration, each main portion having the center deviated from a distal end of each additional portion by a distance d satisfying the following expression (A) circumferentially of the rotor:
• ##EQU33## where D=rotor diameter
• z=the number of stator slots
• p=the number of pole pairs
• each first unit being composed of the steel sheets laminated so that the respective additional portions are inclined in the direction of the one side along the circumference of the rotor relative to the positions of the respective main portions and so that the main portions are piled on upon another, each second unit being composed of the steel sheets laminated so that the respective additional portions are inclined in the direction of the other side along the circumference of the rotor relative to the positions of the respective main portions and so that the main portions are piled on upon another;
• b) rotor bars embedded in the main portions of the respective slots of the rotor core, each unit of the steel sheets having cooling air paths formed by the additional portions;
• and
• c) end rings provided for short-circuiting the rotor bars at both ends of the rotor core, respectively.

A squirrel-cage rotor for use in conjunction with an induction motor of the type including a stator having a slotted stator core and a plurality of stator poles grouped in pairs, wherein the rotor comprises:

• a) a rotor core comprising one or a plurality of first units of steel sheets and one or a plurality of second units of steel sheets, each unit being composed of a plurality of steel sheets each having a number of slot-forming punched portions for forming slots, the number of which differs from the number of slots of a stator core, each punched portion including a main portion and an additional portion extended from the main portion toward the outer circumference of the rotor and inclined in the direction of either one of two sides along the circumference of the rotor relative to the position of the main portion such that each punched portion has an unsymmetrical configuration, each main portion having the center deviated from a distal end of each additional portion by a distance d satisfying the following expression (A) circumferentially of the rotor:
• ##EQU34## where D=rotor diameter
• z=the number of slots in the stator core
• p=the number of pole pairs
• each first unit being composed of the steel sheets laminated so that the respective additional portions are inclined in the direction of the one side along the circumference of the rotor relative to the positions of the respective main portions and so that the main portions are piled one upon another, each second unit being composed of the steel sheets laminated so that the respective additional portions are inclined in the direction of the other side along the circumference of the rotor relative to the positions of the respective main portions and so that the main portions are piled one upon another;
• b) rotor bars embedded in slots of the rotor core formed by the punched portions of the steel sheets laminated, respectively;
• and
• c) end rings provided for short-circuiting the rotor bars at both ends of the rotor core, respectively.