Xiaofang Liu

Optimal design of premium efficiency cage induction motors (IE3 Level) with non-skewed asymmetrical rotor bars based on FEA

To weaken the additional torque and noise caused by slot harmonics field, squirrel cage asynchronous motor with skewed rotor bars are widely used in small and medium cage induction motors. However, with skewed rotor, the distribution of the fundamental fields along the axial direction is non-uniformly, which may cause greater core saturation and higher iron losses. Furthermore, the inter-bar or the transverse currents are also produced by non-insulation between the rotor bars and lamination steels, which also lead to the excess loss significantly, especially for the small and medium motors. Therefore, it is necessary to eliminate the influence of the skewed rotors on the motor losses. In this aspect, a design method of non-skewed rotor bars for cage induction motors is presented, in which the asymmetrical straight rotor bars is adopted to weaken the slot harmonic field, at the same time, the excess loss caused by transverse currents can also be avoided. Therefore, it is helpful to design the small and medium size induction motors with premium efficiency (IE3 level). But the problem is how to design the parameters of the asymmetrical degree, air-gap length, slot combination and closed slot comprehensively.

The influence of rotor slot wedge conductivity on transient stability of turbine generator

In this paper, we establish Field-circuit-network Coupled Time-Step Finite Element Model by the combination of magnetic field equations, electrical circuit and network equations. Based on this mode, we take a 300 MW turbine generator as an example to study the influence of rotor slot wedge material on transient stability and establish the relationship between transient stability limit and rotor slot wedge conductivity. The result shows that the transient stability limit gradually increases as the conductivity of rotor slot wedge changes from σal (conductivity of aluminum alloy) to 0.05σal.

A Design Method for Non-Skewed Small and Medium Cage Induction Motors

This paper presents a design method for non-skewed small and medium cage induction motor based on the finite element analysis, in which the approaches of asymmetrical rotor slots, closed slots, nearly slot combination and reasonable air-gap length are adopted and studied systematically. With this method, the cage induction motors with non-skewed rotor bars can be realized meanwhile, the slot harmonic, which is caused by slot opening, can be eliminated effectively and the efficiency can also be improved apparently. Finally, a design example for a 5.5 kW induction motor is also presented.

A Comparison of the Loss Characteristics in Induction Motors with the Different Core Materials

This paper intends to study the loss characteristics of the induction motors with the different core materials, in which the flux density distribution at the local core positions, including the fundamental and harmonic components, are computed and analyzed by Time-Stepping Finite Element Method (T-S FEM), then the influences of the different core materials on stator and rotor copper losses, as well as, iron losses are further studied.