Grooved Stator Tooth Shoe Geometry for Lower Cogging Torque
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Solution Overview
Problem
Motors experience cogging torque, leading to noise and vibration issues, which affect their performance and quality, and existing designs struggle to effectively reduce this torque through optimal groove design in stator teeth.
Innovation Solution
The motor design incorporates a stator with teeth having a body and a shoe with grooves, where the curvature center of the shoe's inner surface matches the stator core, and the grooves are strategically positioned and sized to reduce cogging torque, with specific ratios and dimensions for the groove width and depth relative to the slot open, and the rotor features magnets with controlled curvature radii and angles to minimize torque ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the motor uses a conventional stator design without optimized groove geometry, then the manufacturing is simpler, but the cogging torque is higher causing noise and vibration
Solution Approach 1:
The tooth structure is segmented into a body portion and a shoe portion with grooves formed in the shoe. This segmentation allows the grooves to be strategically positioned to modify magnetic flux distribution and reduce cogging torque while maintaining structural integrity and simplifying manufacturing compared to completely redesigning the entire tooth geometry.
Solution Approach 2:
The groove geometry is optimized with specific width and depth ratios (width: 0.5-1.5 times slot open width, depth: 0.1-0.3 times tooth effective length) applied locally to the shoe portion. This local optimization reduces cogging torque through controlled magnetic flux paths in the critical region near the slot open, while keeping the rest of the stator structure simple and easy to manufacture.
2Object-affected harmful factors
If the groove width is increased to reduce cogging torque, then the torque ripple decreases, but the motor performance may be compromised
Solution Approach 1:
The groove dimensions are optimized within specific parameter ranges: width between 0.5-1.5 times the slot open width and depth between 0.1-0.3 times the tooth effective length. These parameter changes strike a balance between reducing torque ripple through modified magnetic flux distribution and maintaining motor performance by avoiding excessive groove dimensions that would weaken the tooth structure.
Solution Approach 2:
The groove depth is designed to extend partially into the tooth (0.1-0.3 times the effective length) rather than through the entire tooth. This partial action is sufficient to influence magnetic flux paths and reduce cogging torque while preserving enough tooth material to maintain electromagnetic performance and structural strength.
3Object-affected harmful factors
If the curvature center of the shoe inner surface is positioned at the stator core center, then the cogging torque is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The inner surface of the shoe is designed with a curved geometry whose center coincides with the stator core center. This curvature creates a more uniform magnetic flux distribution in the air gap, effectively reducing cogging torque. The curved geometry can be manufactured using standard molding or machining techniques, making the precision requirement achievable in practice.
Solution Approach 2:
The curvature center of the shoe inner surface is merged with the stator core center, creating a geometric relationship that simplifies the magnetic field distribution. This merging of geometric centers achieves cogging torque reduction through symmetric flux paths while allowing manufacturing using conventional methods, as the curvature can be defined by a single radius from the stator center.
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 significantly reduces cogging torque, improving motor quality by increasing the main cogging order and reducing torque ripple, particularly in high-speed rotations, thereby enhancing the motor's performance and reducing noise.
Implementation Method 1
owing to a difference in permeability between the stator made of a metal material and air of the SO which is an empty space while the rotor rotates, a cogging torque may occur
Implementation Method 2
Motors are devices obtaining rotational forces by converting electrical energy into mechanical energy
Implementation Method 3
the rotor may include a plurality of magnets disposed to face the teeth
Data Source
AI summary
An embodiment provides a stator comprising a stator core having a plurality of teeth and coils wound around the teeth, wherein the tooth includes a body around which the coil is wound and a shoe connected to the body, the shoe includes a plurality of grooves and a curvature center of the inner peripheral surface of the shoe is the same as the center of the stator core.