From the perspective of high-voltage motor winding structure design and the overall development trend of modern high-voltage, high-power motor manufacturing processes, regardless of whether an externally press-fitted or internally press-fitted stator core is used, the coil manufacturing should be carried out in a sealed, air-purified environment, including the high-voltage winding coils and the winding itself. After winding, a vacuum impregnation insulation treatment should be performed. The purpose is to ensure that the motor's insulation performance meets the user's requirements, as well as the product performance and quality requirements under different special operating conditions.
Furthermore, an analysis of innovation among global motor manufacturers reveals that, to meet the demands of energy-efficient and high-performance high-voltage motor design, countries are widely researching and adopting new technologies, processes, and materials for high-voltage winding coil manufacturing to reduce the thickness of the main insulation on one side of the high-voltage winding coil. Practical verification shows that every 1mm reduction in the main insulation thickness increases the motor's design power by 10%. Therefore, the thickness of the main insulation on one side of the high-voltage winding coil will be a marker of the technological design and manufacturing capabilities of the motor industry and motor manufacturers. It can be predicted that the global motor industry will focus its research on the main insulation structure of motors in the future.
Novel insulation structure design for high voltage winding coils
Both theory and practice have proven that the straight section of the high-voltage winding insulation wire located outside the slot is the weakest point of the insulation, due to the increased local field strength concentration effect. Furthermore, the insulated coil experiences significant alternating tensile strain caused by static and dynamic mechanical bending, especially in high-speed motors with few poles. If thermosetting or heat-shrinkable insulation structures are used, the insulation will fracture and peel when the alternating bending strain exceeds the limit of epoxy glass fiber powder mica insulation, which is undesirable for designers.
The design of the stator winding insulation structure of a high-voltage motor and the selection of the single-sided thickness of the main insulation also require consideration of the high rigidity of the winding coils to reduce deformation caused by electromagnetic forces during dynamic operation. Simultaneously, the geometry and dimensions of the winding coils must be strictly controlled to minimize damage to the insulation during the winding process.
In actual production, the tapered interface of the winding coil is the weakest point in insulation and also bears torsional stress. Therefore, to prevent flashover or breakdown of the core during withstand voltage tests at the overlap between the straight portion of the composite box-wound anti-corona treatment molded coil and the tapered interface at the end, in addition to strictly ensuring the overlap position and length dimensions, insulation reinforcement is achieved by starting the wrapping at the slot after straight molding. This traditional insulation structure is mostly used in high-speed motors with few poles. However, since the reinforcement insulation wrapping is done after molding, the two are difficult to bond tightly, and the insulation effect is not ideal. Based on analysis, research, and experiments, a new insulation structure implementation scheme for high-voltage winding coils is adopted, which uses a composite box-wound anti-corona treatment molded coil with reinforced insulation on the straight portion outside the slot.
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