Permanent Magnet Rotor Geometry for Higher Torque in Small Motors
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Solution Overview
Problem
Existing permanent magnet rotors in electrical machines are inefficient in utilizing magnetic material, leading to wasted resources and limited torque due to suboptimal magnetic flux paths, especially in smaller motors, and require new designs for anisotropic magnets.
Innovation Solution
A rotor design featuring radially magnetized permanent magnets with a circular-arc-shaped outer contour and an inner contour defined by a magnetic equipotential line, maximizing the radial thickness of the magnets to 65-95% of the core thickness, ensuring full utilization of magnetic material and allowing both isotropic and anisotropic magnets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the radial thickness of permanent magnets is increased to improve torque, then the torque increases, but the space available in the rotor is limited by the stator bore and rotor shaft, making it impossible to increase magnet thickness indefinitely
Solution Approach 1:
The patent applies local quality by varying the radial thickness of permanent magnets along the circumferential direction. The magnets are thickest at their center (pole center) and taper towards the sides, creating a non-uniform thickness distribution. This allows maximum torque generation at the pole center while reducing overall magnet volume and accommodating space constraints within the rotor.
Solution Approach 2:
The patent employs curved surfaces for the permanent magnets, with the outer contour being circular-arc-shaped and the inner contour being convex. This spherical/curved geometry optimizes the magnetic flux distribution and allows better utilization of the available rotor space compared to flat or rectangular magnet geometries.
2Reliability
If the radial thickness of the rotor core is increased to improve magnetic flux conduction, then the magnetic flux conduction improves, but the overall rotor size increases
Solution Approach 1:
The rotor core is designed with non-uniform thickness, being thickest at the pole centers where maximum magnetic flux conduction is needed and tapering towards the sides. This local quality approach ensures adequate magnetic flux conduction paths where required while minimizing overall rotor core volume and size.
Solution Approach 2:
The patent addresses magnetic flux conduction by optimizing the three-dimensional geometry of the core and magnets rather than simply increasing radial thickness. The curved surfaces and varying thicknesses create efficient flux paths through spatial optimization in multiple dimensions.
3Ease of manufacture
If conventional magnet geometries are used, then manufacturing is simpler, but magnetic material is not fully utilized leading to wasted resources and limited torque
Solution Approach 1:
The patent changes the geometric parameters of the permanent magnets from conventional uniform thickness to a varying thickness profile with convex inner contour and circular-arc outer contour. This parameter optimization maximizes the utilization of magnetic material, ensuring that each portion of the magnet contributes effectively to torque generation while minimizing material waste.
4Device complexity
If the rotor is designed for isotropic magnets, then the design is simpler, but anisotropic magnets cannot be utilized which limits magnetic performance
Solution Approach 1:
The patent creates a universal magnet geometry design that can accommodate both isotropic and anisotropic permanent magnets. The convex inner contour and circular-arc outer contour configuration is optimized to work with different magnet types, allowing the same rotor structure to achieve optimal performance with either magnet type without requiring complete redesign.
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
Optimizes magnetic material usage, reduces waste by up to 50%, enhances torque, and maintains or increases machine performance while eliminating demagnetization, suitable for electric motors under 1 kW.
Implementation Method 1
a rotor for a rotating electrical machine, in particular for an electric motor
Implementation Method 2
radially magnetized permanent magnets arranged along the outer circumference of the rotor
Implementation Method 3
surface recesses of a flux-conducting core which is connected in a rotationally fixed manner to a rotor shaft
Data Source
Figure 1a~1d
Figure 2a~2b
Figure 3a~3c
AI summary
The invention relates to a rotor (1) for a rotating electrical machine, in particular for an electric motor (13), comprising a number (2p) of radially magnetised permanent magnets (2) arranged along the outer circumference of the rotor (1) in surface recesses (7) of a flux-conducting core (30), which is rotationally fixed to a rotor shaft (11) or formed by a part of a rotor shaft. When viewed as a cross-section, the permanent magnets (2) are defined by a circular-arc-shaped outer contour (8) with a radius corresponding to the outer radius (R2) of the rotor (1), and an inner contour (9) in such a way that the radial thickness (xmax) of the permanent magnets (2) is greatest at their centre and reduces towards the sides in the circumferential direction. The maximum radial thickness (xmax) of the permanent magnets is 65-95% of the maximum radial thickness (Dmax) of the core (3). In addition, the inner contour (9) is substantially described by a magnetic equipotential line (10).