Permanent magnet-embedded motor and compressor
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Solution Overview
Problem
Permanent-magnet-embedded electric motors that utilize reluctance torque to enhance efficiency often experience torque ripple, leading to increased current requirements and reduced efficiency due to magnetic path blockage by slits, which also cause vibration and noise.
Innovation Solution
A rotor core structure with alternating core blocks, one without slits and the other with slits, is used to minimize torque ripple while maintaining torque efficiency by optimizing the ratio of core block lengths in the axial direction, allowing effective magnetic flux usage and reducing leakage flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If slits are disposed on the rotor core to reduce torque ripple, then torque ripple is reduced, but magnetic flux path is blocked causing reduced torque and efficiency
Solution Approach 1:
The rotor core is segmented into multiple core blocks in the axial direction, with alternating blocks having slits and non-slits. This segmentation allows different regions to serve different functions: slit blocks reduce torque ripple while non-slit blocks maintain magnetic flux paths for torque generation.
Solution Approach 2:
Different regions of the rotor core are given different properties: some core blocks have slits (for torque ripple reduction) while others don't (for torque maintenance). The axial lengths of these blocks are optimized to achieve the desired balance between torque ripple reduction and torque preservation.
2Object-generated harmful factors
If slits are disposed on the rotor core to reduce torque ripple, then torque ripple is reduced, but current requirement increases due to reduced efficiency
Solution Approach 1:
The rotor core is segmented into multiple core blocks in the axial direction, with alternating blocks having slits and non-slits. This segmentation allows different regions to serve different functions: slit blocks reduce torque ripple while non-slit blocks maintain magnetic flux paths for torque generation.
Solution Approach 2:
Different regions of the rotor core are given different properties: some core blocks have slits (for torque ripple reduction) while others don't (for torque maintenance). The axial lengths of these blocks are optimized to achieve the desired balance between torque ripple reduction and torque preservation.
3Object-generated harmful factors
If slits are disposed on the rotor core to reduce torque ripple, then torque ripple is reduced, but vibration and noise increase
Solution Approach 1:
The rotor core is segmented into multiple core blocks in the axial direction, with alternating blocks having slits and non-slits. This segmentation allows different regions to serve different functions: slit blocks reduce torque ripple while non-slit blocks maintain magnetic flux paths for torque generation.
Solution Approach 2:
Different regions of the rotor core are given different properties: some core blocks have slits (for torque ripple reduction) while others don't (for torque maintenance). The axial lengths of these blocks are optimized to achieve the desired balance between torque ripple reduction and torque preservation.
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 torque ripple while preventing a decrease in torque at the same current, enhancing motor efficiency and reducing vibration and noise.
Implementation Method 1
permanent-magnet-embedded electric motors achieving high efficiency by using rare earth magnets with high residual magnetic flux density and coercivity in a rotor
Implementation Method 2
the permanent magnets are embedded in the rotor so as to be able to use not only magnet torque but also reluctance torque
Implementation Method 3
the slits block a magnetic path of a magnetic flux to cause a reduction in torque obtained at the same current
Data Source
Figure 1
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Figure 3
AI summary
A rotor 3 of a permanent-magnet-embedded electric motor includes an annular rotor core 10 having a plurality of magnet insertion holes 13 formed in a circumferential direction, and permanent magnets 11 inserted into the magnet insertion holes 13, respectively. The rotor core 10 is formed by alternately stacking a core block 10a and a core block 10b in an axial direction of the rotor core 10, the core block 10a not having slits 15a and 15b between each of the magnet insertion holes 13 and a circumferential surface of the rotor core 10, and the core block 10b having the slits 15a and 15b between each of the magnet insertion holes 13 and the circumferential surface of the rotor core 10. The slit 15a and an end 11a of the permanent magnet 11 are arrayed in a radial direction, and the slit 15b and an end 11b of the permanent magnet 11 are arrayed in the radial direction.