Comparative study on structure of laminated-rotor high-speed induction machine

The circumference of the high speed induction motor's rotor speed can reach above 100m/min, which leads to the mechanical strength of the rotor unreliable. To reduce the eddy current loss, laminated-rotor structure is always used, which makes it more difficult to meet the strength requirement. To solve problems above, a round bar shape and a drop bar shape are designed. The differences between the two kinds of scheme on magnetic properties and stress characteristics are compared through 3D finite element analysis. Rotor with round bars shows low mechanical stress, but high magnetic flux density in the rotor teeth and high current density in the rotor bars. Rotor with drop bars is just opposite. In this paper, optimized slot is presented. The results show that using this type of bar shape can make it reasonable in the aspects of both the electromagnetic performance and stress. Finally, the designed bar shape is optimized.