Segmented Stator Slot Structure for Lower Cogging Torque
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Solution Overview
Problem
Existing rotary electric machine stators face challenges in assembly simplicity, effective slot filling, and electromagnetic performance, particularly in reducing torque ripples and electromagnetic disturbances due to open slots towards the air gap.
Innovation Solution
A stator design featuring a radially interior toothed ring with bridges connecting teeth, closed slots on the air gap side, and a radially outer yoke formed from assembled sectors, which enhances mechanical reinforcement, reduces vibrations, and improves electromagnetic performance by minimizing cogging torque and electromagnetic disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If slots are entirely open or semi-open towards the air gap to allow coil introduction, then ease of manufacture and assembly is improved, but electromagnetic disturbances increase and torque ripples occur
Solution Approach 1:
The slot is divided into two distinct parts: an open upper portion for coil insertion and a closed lower portion near the air gap. This segmentation allows the slot to simultaneously provide easy access for manufacturing while eliminating the harmful electromagnetic effects associated with fully open slots
Solution Approach 2:
Different regions of the slot have different opening characteristics. The upper region remains open to facilitate coil introduction, while the lower region is closed to prevent electromagnetic disturbances. This local differentiation of quality resolves the contradiction between manufacturing ease and electromagnetic performance
2Ease of operation
If slots are entirely open towards the air gap for simple assembly, then ease of operation is improved, but cogging torque increases and vibrations occur
Solution Approach 1:
The slot structure is segmented into open and closed portions, allowing simple assembly through the open upper part while the closed lower part eliminates the cogging effect by preventing flux leakage paths that cause torque instability
Solution Approach 2:
The closed lower portion of the slot preemptively prevents the formation of cogging torque by blocking the magnetic flux paths before they can cause harmful interactions between stator teeth and rotor magnets, thereby stabilizing the torque composition
3Ease of manufacture
If slots are semi-open with thinner portions between teeth, then ease of manufacture is improved, but iron losses increase and torque ripples occur
Solution Approach 1:
The slot is segmented so that only the necessary upper portion remains open for manufacturing access, while the lower portion is closed to prevent flux fringing. This eliminates the thin portions between teeth that cause excessive iron losses while maintaining manufacturing simplicity
4Manufacturing precision
If yoke is formed in one piece with the ring, then manufacturing precision is improved, but device complexity increases for large stators
Solution Approach 1:
The yoke is divided into multiple detachable sectors that can be assembled around the toothed ring. This segmentation reduces the complexity of manufacturing and assembling large stators while maintaining the structural integrity and precision of the complete yoke through careful design of the sector interfaces
Data Source
AI summary
A stator (2) for a rotary electric machine (1), comprising:—a radially interior ring (25) comprising teeth (23) and slots (21) opening radially towards the outside and extending between the teeth, bridges of material (27) connecting two adjacent teeth to their base and defining the bottoms of the slots between these teeth,—coils (22) arranged in the slots, having electrical conductors arranged in an ordered fashion in the slots (21), and—a radially outer yoke (29) attached in contact with the ring, the yoke being formed of assembled sectors (30).