Rotating Electric Machine Stator Tooth Shape for Noise Reduction
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Solution Overview
Problem
Conventional rotating electric machines for electric vehicles face challenges in reducing vibration and noise due to radial electromagnetic excitation force harmonics, and existing solutions are not flexible enough to accommodate various combinations of poles and stator teeth.
Innovation Solution
The rotating electric machine features a stator with teeth grouped in units equal to the greatest common divisor of the number of poles and slots, with at least one tooth in each group having a distinct distal end shape, which reduces harmonics amplitude of the radial electromagnetic excitation force without altering the periodic boundary condition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the stator core teeth are configured with a limited number of slots (2n×s) to reduce electromagnetic excitation force of 6f, then electromagnetic noise is reduced, but the design cannot be flexibly applied to other forms of stator core structures with different numbers of slots
Solution Approach 1:
The patent applies local quality by making only specific teeth (one tooth per tooth group) have a different distal end shape, while other teeth maintain the same shape. This localized modification is sufficient to reduce harmonics amplitude of radial electromagnetic excitation force without requiring changes to the entire stator core structure, thereby enabling flexible application to various slot configurations.
Solution Approach 2:
The patent changes the geometric parameter of at least one tooth's distal end shape within each tooth group. This parameter change disrupts the periodicity of the magnetic circuit, reducing harmonics amplitude and electromagnetic noise, while the overall stator core structure and slot number remain flexible for different applications.
2Stability of the object's composition
If conventional preventive measures are applied primarily for torque ripples, then torque smoothness is improved, but vibration and noise due to harmonics of radial electromagnetic excitation force are not adequately reduced
Solution Approach 1:
The patent focuses on locally modifying the distal end shape of specific teeth rather than applying uniform measures across the entire stator. This localized approach specifically targets the reduction of radial electromagnetic excitation force harmonics that cause vibration and noise, complementing conventional torque ripple reduction measures.
Solution Approach 2:
The patent introduces asymmetry by making at least one tooth in each tooth group have a different distal end shape from the others. This asymmetric configuration disrupts the periodicity of the magnetic circuit, reducing harmonics amplitude and thereby reducing vibration and noise, while maintaining torque smoothness.
3Object-affected harmful factors
If the shape and pitch of stator teeth are changed to reduce electromagnetic noise, then vibration and noise are reduced, but the method cannot be flexibly applied to various combinations of number of poles and number of stator teeth
Solution Approach 1:
The patent creates a universal solution by defining tooth groups based on the greatest common divisor of the number of poles and stator slots. This approach can be applied to any combination of poles and slots, making the noise reduction method universally applicable across different machine configurations while maintaining flexibility.
Solution Approach 2:
The patent modifies only the distal end shape of at least one tooth per tooth group, leaving other tooth parameters and the overall stator structure unchanged. This minimal local modification achieves noise reduction while preserving compatibility with various pole and slot combinations.
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 configuration effectively reduces vibration and noise levels by minimizing harmonics amplitude, improving the machine's performance across different rotational speeds and stator configurations.
Implementation Method 1
The electromagnetic excitation force that causes the vibration/noise arising from the rotating electric machine main body is applied in three directions, that is, radially, tangentially, and axially
Implementation Method 2
a magnetic circuit is formed across each of the in-phase teeth and the out-of-phase teeth, with a difference being provided in magnetic resistance of each magnetic circuit so that the number of magnetic fluxes passing through the teeth will be substantially equal between the two sets of teeth
Data Source
AI summary
Provided is a rotating electric machine including a rotor and stator fitted with various numbers of poles and slots and adapted to reduce vibration/noise of the machine. The rotating electric machine in accordance with an aspect of the present invention includes a stator having an S number of teeth, and a rotor disposed in the stator with a gap intervening between the stator and the rotor. The plurality of teeth in the stator are grouped in units of the number of teeth that is equal to a value “m” or a value “d”, the value “m” being obtained by dividing the number of stator slots, S, by the greatest common divisor N of the number of poles, P, and the number of stator slots, S, the value “d” being an aliquot of “m”. At least one tooth in each of the tooth groups has a distal end different in shape from distal ends of other teeth belonging to the same tooth group, and the plurality of tooth groups have the same configuration.