Interior Permanent Magnet Rotor Slot Shape for Low Vibration Torque
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Solution Overview
Problem
The use of arc-shaped permanent magnets in interior permanent magnet motors leads to unbalanced magnetic flux density on the rotor outer peripheral surface, causing vibration and potential demagnetization due to local concentration of magnetic flux and blockage by slits, resulting in unbalanced rotor magnetic attraction force.
Innovation Solution
The design includes a rotor core with arc-shaped magnet insertion holes and slits positioned on the radially outer side, featuring concave portions at the ends of the magnet insertion holes to reduce unbalanced magnetic flux density by minimizing the linkage of stator magnetic flux in the q-axis phase, thereby reducing vibration and demagnetization risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If arc-shaped permanent magnets are arranged with convex portion toward radially inner side to increase magnet surface area, then driving torque increases, but magnetic flux density becomes unbalanced on rotor outer peripheral surface causing vibration
Solution Approach 1:
The magnet insertion hole is designed with different curvature radii in different regions: a first curvature radius in the radial direction and a second curvature radius in the axial direction, creating local quality variations that optimize magnetic flux distribution while maintaining high magnet surface area for increased driving torque
Solution Approach 2:
The magnet insertion hole employs asymmetric curvature design where the convex portion faces the radially inner side with specific curvature radii relationships (first curvature radius < second curvature radius), creating intentional asymmetry to balance magnetic flux density distribution and reduce vibration
2Object-affected harmful factors
If slits are formed in rotor core to reduce unbalance in rotor magnetic attraction force, then vibration is reduced, but magnetic flux path is blocked causing local concentration of magnetic flux
Solution Approach 1:
The slit design incorporates local quality variations with different widths at different positions, and the magnet insertion hole curvature design compensates for flux concentration effects in specific regions while maintaining the vibration-reducing function of the slits
3Productivity
If magnet insertion hole is curved into arc shape with convex portion toward center to increase magnet area, then driving efficiency improves, but stator magnetic flux linkage is reduced in q-axis phase
Solution Approach 1:
The curvature radii parameters of the magnet insertion hole are optimized with specific relationships (first curvature radius in radial direction, second curvature radius in axial direction, where first < second), changing geometric parameters to simultaneously improve magnet surface area and magnetic flux linkage
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 suppresses unbalanced magnetic flux density on the rotor outer peripheral surface, reducing vibration and maintaining magnetic attraction force balance while enhancing driving torque and efficiency by optimizing magnetic flux distribution.
Implementation Method 1
the magnetic flux generated by a stator coil is hardly linked
Implementation Method 2
the magnetic flux generated by the permanent magnets so as to increase a driving torque of the motor
Implementation Method 3
the magnetic flux is concentrated in the core regions at arc-surface ends of the magnetic insertion hole
Data Source
AI summary
In an interior permanent magnet motor, a magnet insertion hole of a rotor core is curved into an arc shape, and a convex portion side of the arc shape is arranged on a center side of a rotor. The magnet insertion hole has a first line, a second line, and a pair of third lines. The first line is located on the radially outer side of the second line. Each of the third lines connects the first line and the second line to each other. The first line includes an arc portion and a pair of concave portions. Each of the concave portions is located at an end of the arc portion of the first line.