Segmented Stator Slot Pitch Layout for Lower Cogging Torque
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Solution Overview
Problem
Electric machines with rotors and permanent magnet poles suffer from torque ripple due to cogging, which is challenging to address through conventional methods, and prior stator designs have mechanical strength issues and alignment problems, especially with thinner outermost teeth.
Innovation Solution
The stator design features wider outermost teeth, with a width over 50% of intermediate teeth, and a non-uniform slot pitch distribution, which increases mechanical strength and facilitates assembly, while quasi-skewing the stator relative to the rotor to reduce cogging torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the outermost teeth are made thinner to reduce material usage, then the quantity of substance is reduced, but the mechanical strength and alignment precision deteriorate
Solution Approach 1:
The patent applies local quality by making the outermost teeth wider than the intermediate teeth. Specifically, the outermost teeth have a width of at least 0.6 times the slot pitch, while intermediate teeth have a width of at least 0.5 times the slot pitch. This local variation in tooth width provides enhanced mechanical strength and alignment precision at the outermost positions where these properties are most critical, while maintaining reasonable material usage overall.
2Quantity of substance
If the outermost teeth are made thinner to reduce material usage, then the quantity of substance is reduced, but the manufacturing precision deteriorates
Solution Approach 1:
The patent applies local quality by making the outermost teeth wider than the intermediate teeth. Specifically, the outermost teeth have a width of at least 0.6 times the slot pitch, while intermediate teeth have a width of at least 0.5 times the slot pitch. This local variation in tooth width provides enhanced alignment precision at the outermost positions where these properties are most critical, while maintaining reasonable material usage overall.
3Device complexity
If conventional uniform slot pitch is used, then the device complexity is reduced, but the cogging torque increases
Solution Approach 1:
The patent applies local quality by creating different slot pitch regions. The slot pitch between adjacent stator slots is at least 0.6 times the circumferential length of the stator sector, while the slot pitch between stator slots of adjacent stator sectors is at least 0.5 times the circumferential length of the stator sector. This local variation in slot pitch breaks the uniform periodicity that causes cogging torque, reducing the harmful effect while maintaining manageable device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances mechanical strength, simplifies assembly, and reduces cogging torque by breaking the uniform periodicity of stator teeth, improving performance in both large and small electric machines.
Implementation Method 1
The pack of stator sheets may be pressed together between the end plates in a press
Implementation Method 2
The axial support beams may be welded to the end plates
Implementation Method 3
Each stator sector may be made of a pack of thin electromagnetic stator sheets
Data Source
AI summary
An annular stator provided with axial stator slots and stator teeth formed between adjacent stator slots. Each stator slot receives a conductor of a stator winding. The stator is formed of stator sectors. Each stator sector includes two outermost stator teeth and intermediate stator teeth between the two outermost stator teeth. A width of the two outermost stator teeth is equal. Adjacent stator slots within each stator sector are distanced by a first slot pitch and adjacent stator slots belonging to different stator sectors are distanced by a second slot pitch. The first slot pitch is smaller than the second slot pitch.