Rotating Electric Machine Stator Air Gap Asymmetry
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Solution Overview
Problem
Conventional rotating electric machines for hybrid and electric vehicles experience significant electromagnetic noise due to unbalanced electromagnetic excitation between stator teeth, leading to vibrations and noise disturbances, particularly in the low to high-speed range.
Innovation Solution
A rotating electric machine design with a stator core having 2n×s teeth and slots, where coils are wound in a shifted configuration to balance flux linkages between same-phase-intermediate and different-phase-intermediate teeth, using magnetic resistance adjusting means to equalize electromagnetic excitation, thereby canceling out radial vibrations and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If coils are wound at adjacent slot groups with equal pitch in a conventional rotating electric machine, then the structure is simple and easy to manufacture, but unbalanced electromagnetic excitation occurs between stator teeth causing significant electromagnetic noise and vibration
Solution Approach 1:
The patent applies asymmetry by intentionally creating different magnetic resistance paths for same-phase-intermediate teeth and different-phase-intermediate teeth. This is achieved through asymmetric magnetic resistance adjusting means (different air gap widths or different cross-sectional areas of magnetic paths) to balance the electromagnetic excitation between adjacent stator teeth, thereby reducing the harmful electromagnetic noise while maintaining a relatively simple coil winding structure
2Object-generated harmful factors
If magnetic resistance adjusting means is added to balance flux linkages between teeth, then electromagnetic noise is reduced, but device complexity increases
Solution Approach 1:
The patent applies local quality by making localized modifications to specific regions of the stator core rather than changing the entire structure. The magnetic resistance adjusting means is applied locally at specific same-phase-intermediate teeth and different-phase-intermediate teeth, allowing precise control of magnetic flux distribution only where needed to balance electromagnetic excitation and reduce noise
3Object-generated harmful factors
If air gap width is varied between same-phase-intermediate tooth and different-phase-intermediate tooth, then flux linkage balance is achieved, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by pre-designing and pre-setting different air gap widths or different cross-sectional areas during the manufacturing process. This allows the magnetic resistance difference to be built-in from the start, ensuring proper flux linkage balance without requiring complex real-time adjustments or high-precision dynamic control during operation
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
The solution effectively suppresses stator vibration and reduces electromagnetic noise by balancing flux linkages and magnetic resistance between teeth, resulting in a substantial reduction of electromagnetic excitation and noise levels, particularly at the 6f frequency range.
Implementation Method 1
the number of flux linkages passing through acquires balance with each other
Implementation Method 2
providing a difference in the magnetic resistance of a magnetic circuit formed for each of the same-phase-intermediate tooth and different-phase-intermediate tooth
Implementation Method 3
The electromagnetic excitation applied to the teeth by supply of the alternating current to the stator coil will be out of balance between the teeth
Implementation Method 4
The radial vibration occurring at the stator core due to the imbalance of the component in the radial direction causes the air in contact with the outer circumferential face or inner circumferential face of the stator core to vibrate
Data Source
AI summary
In a rotating electric machine that is formed of a distribution winding motor with two slots per each pole and each phase, a stator core includes an air gap of a constant width dg1 between the leading end of a same-phase-intermediate tooth and the outer circumferential face of a rotor core, and an air gap of a width not uniform in the circumferential direction between the leading end of a different-phase-intermediate tooth and the outer circumferential face of the rotor core, with a width dg2 (>dg1) as the largest value. A magnetic circuit having a magnetic resistance higher than that of the same-phase-intermediate tooth is formed at the different-phase-intermediate tooth. By establishing a difference in the width of the air gap such that the number of flux linkages at the different-phase-intermediate tooth reduced by the increased magnetic resistance is substantially equal to the number of flux linkages at the same-phase-intermediate tooth, the electromagnetic excitation applied in directions opposite to each other acquire balance so as to cancel each other, allowing vibration at the stator core to be suppressed.