Hairpin Winding Stator Assembly for Lower Torque Ripple
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Solution Overview
Problem
Current methods for manufacturing stator assemblies of hairpin winding motors face issues with high defective rates, increased cogging torque and torque ripples, and inadequate fixing force of hairpin coils, leading to reduced productivity and performance.
Innovation Solution
The solution involves a stator assembly design where hairpin coils are continuously connected in a circumferential direction, with a stator core that includes a ring core and pin cores to securely fix the coils, and a manufacturing method that uses a fixing jig to support pin cores during assembly, reducing defects and improving the fixing force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If shoes are formed on end portions of teeth and hairpin coils are inserted in axial direction, then productivity is improved, but defective rate increases due to welding failures
Solution Approach 1:
The patent removes the shoes from the end portions of the teeth, extracting the problematic component that caused welding failures. This eliminates the need for welding operations on hairpin coils while maintaining the fixing function through alternative means (press-fitting or interference fit), thereby resolving the contradiction between productivity and defective rate.
Solution Approach 2:
Instead of inserting hairpin coils in the axial direction through shoes, the patent inverts the approach by inserting coils in the radial direction without shoes. This fundamental reversal of the insertion method eliminates the welding process entirely, reducing defective rates while maintaining assembly efficiency.
2Reliability
If shoes of teeth are removed and hairpin coils are inserted in radial direction, then defective rate is reduced, but cogging torque and torque ripples increase
Solution Approach 1:
The patent applies local quality by creating asymmetric slot designs with different widths at the top and bottom, and by strategically positioning hairpin coils with varying insertion depths. This local variation in coil arrangement compensates for the absence of shoes, reducing cogging torque and torque ripples while maintaining the shoe-less structure that lowers defective rates.
Solution Approach 2:
The patent changes geometric parameters of the slot and coil configuration, specifically the slot width ratio (top width to bottom width) and coil insertion depth ratios. By optimizing these parameters, the patent reduces magnetic asymmetry that causes cogging torque, thereby resolving the contradiction between reduced defective rates and minimized torque ripples.
3Productivity
If hairpin coils are twisted and bent to wind, then productivity is improved, but insulation performance degrades due to film damage
Solution Approach 1:
The patent applies preliminary action by pre-forming the hairpin coils with the exact shape and curvature needed for the slot before insertion. The coils are manufactured in a controlled environment with proper insulation coating applied, eliminating the need for high-load twisting and bending operations that would damage the insulation film during assembly.
Solution Approach 2:
The patent creates a precise copy of the final coil shape during the manufacturing process itself, using molding or other forming techniques to create pre-shaped coils that fit the slot geometry perfectly. This eliminates the need for post-manufacturing deformation operations that could compromise insulation integrity.
Data Source
AI summary
A stator assembly of a hairpin winding motor including hairpin coils continuously connected along a circumferential direction to form a coil winding; and a stator core configured to fix the hairpin coils. Outer circumferential surfaces of the hairpin coils formed in the circumferential direction contact an inner circumferential surface of the stator core.