Two-Layer IPM Rotor Open-Angle Layout for Torque and Strength
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Solution Overview
Problem
Existing double-layer interior permanent-magnet rotors face challenges in maintaining both torque performance and structural strength due to centrifugal stress exceeding mechanical strength limits, particularly when bridges on the outer circumferential side are open or hollowed, leading to deformation and fracture risks.
Innovation Solution
A double-layer interior permanent-magnet rotor design with specific accommodation hole configurations, including non-communicating outer holes and communicating inner holes, sets inner-side open angles equal to or higher than outer-side open angles, facilitating a one-layer cut that balances torque and stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If bridges on the outer circumferential side are opened to reduce leakage flux, then torque performance is improved, but centrifugal stress exceeds mechanical strength causing deformation and fracture
Solution Approach 1:
The rotor core is divided into two distinct layers: an inner layer with opened bridges for torque optimization and an outer layer with closed bridges for mechanical strength. This segmentation allows each layer to fulfill its specific function without compromising the other.
Solution Approach 2:
The solution transitions from a single-layer structure to a two-layer radial structure. By adding the outer layer, the design addresses the mechanical strength deficiency while preserving the torque-generating capability of the inner layer.
2Strength
If magnets are made distant from each other with thicker bridges to reduce deformation, then structural strength is improved, but rotor weight increases and lightening becomes difficult
Solution Approach 1:
The rotor core is segmented into two layers with different bridge thicknesses. The inner layer has thicker bridges for strength, while the outer layer has thinner bridges for weight reduction. This allows optimization of both strength and weight simultaneously.
Solution Approach 2:
Different regions of the rotor core have different structural properties. The inner layer has thicker bridges where mechanical strength is critical, while the outer layer has thinner bridges where weight reduction is prioritized. Each local region is optimized for its specific functional requirements.
3Stress or pressure
If outer bridges are cut to be hollowed to reduce centrifugal stress, then stress is reduced, but torque in medium-speed to high-speed range decreases
Solution Approach 1:
The rotor core is divided into two layers with different bridge configurations. The inner layer has hollowed bridges for stress reduction, while the outer layer has solid bridges for torque maintenance. This segmentation allows simultaneous optimization of stress and torque characteristics.
Solution Approach 2:
By adding the outer layer dimension, the design can have hollowed inner bridges for stress reduction while maintaining solid outer bridges for torque generation, achieving both objectives that cannot be met in a single layer.
4Ease of manufacture
If inner-side open angle is made equal to or higher than outer-side open angle, then a one-layer cut is enabled simplifying manufacturing, but torque characteristics may be affected
Solution Approach 1:
The inner and outer layers have asymmetric open angle configurations. The inner layer has larger or equal open angles for manufacturing simplicity, while the outer layer has smaller open angles optimized for torque characteristics. This asymmetric design allows each layer to be optimized independently.
Solution Approach 2:
The rotor core is segmented into two layers that can be manufactured independently with different open angle specifications. This allows the inner layer to be optimized for ease of manufacturing while the outer layer is optimized for torque performance.
Data Source
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AI summary
According to embodiments, a double-layer interior permanent-magnet rotor (100) includes: a rotor shaft (110); a rotor core (120) including first and second outer side accommodation holes (121, 122) and first and second inner side accommodation holes (124, 125); first and second outer side magnets (131, 132); and first and second inner side magnets (133, 134). The first inner side accommodation hole (124) and the second inner side accommodation hole (125) communicate with the outer side of the outer circumference. A value of an inner-side open angle Θb1 at which radially outer side walls (124a) and (125a) of the inner side accommodation holes open toward a radially outer side is from a prescribed value to a value of an outer-side open angle Θa at which radially outer side walls (121a, 122a) of the outer side accommodation holes open toward the radially outer side.