ABSTRACT
 
 

Thin metal laminations are used to minimize the eddy current loss in the stator cores of high-speed, high-performance induction motors. The conventional fabrication technique, however, introduces limitations on the thickness of laminations, the dimensional accuracy of the assembled stator cores, and the production economy. These limitations greatly hamper the application of high-speed induction motors in industry.

In this study, a novel spray-forming technique, the Uniform Droplet Spray (UDS) process, was employed to produce thin laminations. Pure tin was used to study the feasibility of applying the UDS process to fabricate laminations. Based on droplet spray models, this research characterized and optimized the process design parameters, such as droplet thermal state, mass flux distribution, deposit thermal state and substrate motion, to obtain desired lamination geometry and quality. A layer of 127 µm thick lamination was produced by spraying 200 µm droplets. Surface flatness and uniformity of laminations were improved by choosing the proper mass flux distribution and by increasing the degree of deposit overlap between adjacent path segments and between layers. The surface or bulk porosity was reduced by spraying high liquid fraction droplets onto a sufficiently high temperature substrate. An acrylic lacquer was applied between the tin laminations to provide electrical insulation. The insulation properties were evaluated by a standard test method and an equivalent circuit model was presented to analyze the insulation behavior. The results suggest that the effectiveness of insulation depends on the electrical resistivity, thickness and the uniformity of the insulation layers.

Finally, as a proof-of-concept, a five-layer tin laminate was produced to demonstrate the suitability of the UDS process. Future work for silicon-iron (Fe-Si) laminations is also suggested.
 
 

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