Variable-Reluctance Machine Closed Stator Notches Torque Ripple
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Solution Overview
Problem
Synchronous electrical machines with variable reluctance assisted by permanent magnets experience significant torque ripple and associated vibrations due to open stator notches, leading to discomfort in use.
Innovation Solution
The design incorporates a stator with closed oblong notches that extend axially, featuring a low semi-circular wall near the internal stator wall and a higher semi-circular wall further out, creating a continuous air gap and reducing aerodynamic noise, while the rotor includes flux barriers formed by inclined perforations to direct magnetic flux effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If open stator notches are used to receive armature windings, then the machine structure is simpler and easier to manufacture, but torque ripple and vibrations increase significantly
Solution Approach 1:
The notch is segmented into multiple walls (first wall, second wall, third wall, fourth wall) that collectively form a closed structure. This segmentation allows the notch to maintain its winding-receiving function while blocking the harmful magnetic flux paths that cause torque ripple, thus resolving the contradiction between manufacturing simplicity and torque ripple reduction.
Solution Approach 2:
The invention converts the potentially harmful open notch structure into a beneficial closed structure. By closing the notch with additional walls, the harmful magnetic flux leakage is eliminated, transforming the notch from a source of torque ripple into a controlled magnetic circuit element that maintains ease of manufacture while reducing vibrations.
2Ease of manufacture
If open stator notches are used, then manufacturing is easier, but acoustic noise increases due to air gap variations
Solution Approach 1:
The notch is divided into multiple wall segments that collectively form a closed structure. This segmentation maintains the simplicity of manufacturing individual wall components while the assembled closed structure eliminates air gap variations, thereby reducing acoustic noise without complicating the manufacturing process.
Solution Approach 2:
Instead of leaving the notch open as in conventional designs, the invention inverts the approach by closing the notch with additional walls. This inversion eliminates the air gap variations that cause acoustic noise while maintaining ease of manufacture through modular wall construction.
3Object-generated harmful factors
If closed notches with multiple walls are implemented, then torque ripple and acoustic noise are reduced, but device complexity increases
Solution Approach 1:
The closed notch is segmented into four distinct walls, each serving a specific function in blocking magnetic flux paths. This segmentation reduces torque ripple through improved magnetic circuit control while keeping device complexity manageable by using simple planar wall structures that can be manufactured and assembled independently.
Solution Approach 2:
The closed notch structure provides local quality improvement at critical positions where magnetic flux leakage occurs. By adding walls only at specific locations within the notch rather than redesigning the entire stator, the invention reduces torque ripple and acoustic noise while minimizing the increase in overall device complexity.
4Object-generated harmful factors
If closed notches with multiple walls are implemented, then acoustic noise from air gap variations is reduced, but device complexity increases
Solution Approach 1:
The closed notch is divided into multiple wall segments that can be manufactured and positioned independently. This segmentation reduces acoustic noise by eliminating air gap variations while keeping device complexity manageable through modular construction, where each wall segment is a simple component that contributes to the overall closed structure.
Solution Approach 2:
The closed notch structure improves local quality at the notch regions where acoustic noise originates from air gap variations. By implementing the closed structure only at these critical locations rather than throughout the entire stator, the invention reduces acoustic noise while minimizing the increase in 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 configuration significantly reduces torque ripple and acoustic noise, resulting in smoother operation and reduced vibrations compared to machines with open notches.
Implementation Method 1
perforations to create flux barriers allowing the magnetic flux of the magnets to be directed radially towards the stator
Implementation Method 2
stator which carries electrical windings making it possible to generate a magnetic field making it possible to drive the rotor in rotation
Implementation Method 3
The notches have an oblong section with a low wall at a distance from the wall of the stator, a high wall and two faces connecting the walls
Data Source
Figure 1~2
Figure 3~4
AI summary
The present invention relates to an electric machine comprising a rotor (10) and a stator (12) comprising a wall (32) opposite the rotor, said stator carrying a multiplicity of radial notches disposed circumferentially along said stator. According to the invention, the notches (36) comprise a bottom wall (38) some distance (E) from the wall of the stator so as to form a multiplicity of closed notches.