Analysis of Effects of Magnetic Slot Wedges on Characteristics of Large Induction Motors

Magnetic slot wedges are often used to improve starting performance of large induction motors. In this paper we have investigated – through simulation – the effects of the wedges on the performance characteristics of the motor and core losses under no load condition. Both analytical and hybrid two-dimensional field-circuit models have been used. In order to reliably establish the parameters of the end connections of the rotor cage, whose values significantly influence the results of simulation, a three-dimensional model was developed, also useful for verification purposes at standstill. The simulation has demonstrated the effects of the wedges on the starting performance but revealed little influence on the core losses

Equivalent Permeability of Step-Lap Joints of Transformer Cores: Computational and Experimental Considerations

The paper develops an efficient computational method for establishing equivalent characteristics of magnetic joints of transformer cores, with special emphasis on step-lap design. By introducing an equivalent material, the method allows the real three-dimensional structure of the laminated thin sheets to be treated computationally as a two-dimensional problem and enables comparative analysis of designs. The characteristics of the equivalent material are established by minimizing the magnetic energy of the system. To verify the proposed approach, a series of experiments have been conducted. First, the anisotropic characteristics of the step-lap were established, and then space components of the flux density at specified positions measured. This enabled detailed analysis of the flux distribution in the step-lap region, in particular the way in which the flux travels between the laminations close to the air-gap steps. Encouraging correlation between the homogenized 2-D model and experiment has been observed

Variation of additional losses at no-load and full-load for a wide range of rated power induction motors

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