Curved Stator Tooth Geometry for Lower Eddy Current Loss
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Solution Overview
Problem
Eddy current loss in electric motors with flat-square coils increases due to the larger surface area, reducing energy efficiency and output power density.
Innovation Solution
A stator design with teeth having a flared tip portion and a groove on the back yoke, where the inner circumferential surface features a first region with a radially inward curvature and a second region with a radially outward curvature, and the coil is formed of rectangular cross-section electric wire, optimizing the magnetic flux distribution to reduce eddy current loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If flat-square coils are used to improve space factor, then the space utilization is improved, but eddy current loss increases due to larger surface area
Solution Approach 1:
The tooth inner circumferential surface is divided into two regions with different curvature characteristics: a first region with radially inward curvature and a second region with radially outward curvature. This local differentiation of surface geometry optimizes magnetic flux distribution in different zones, reducing eddy current loss while maintaining the space factor benefits of flat-square coils.
2Use of energy by moving object
If rectangular wires are used to improve energy efficiency, then space factor improves, but output power density is reduced due to increased eddy current loss
Solution Approach 1:
The invention changes the geometric parameters of the tooth inner circumferential surface by introducing specific curvature radii in different regions. The first region has a center of curvature located radially inward, while the second region has a center of curvature located radially outward. This parameter optimization reduces eddy current loss, thereby improving energy efficiency while maintaining output power density.
3Ease of manufacture
If the inner circumferential surface is made flat to simplify manufacturing, then manufacturing is easier, but magnetic flux distribution is suboptimal leading to higher eddy current loss
Solution Approach 1:
Instead of a flat inner circumferential surface, the invention employs curved surfaces with specific radius characteristics. The first region features a center of curvature located radially inward from the inner circumferential surface, while the second region features a center of curvature located radially outward. This curvature optimization improves magnetic flux distribution and reduces eddy current loss.
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 design enhances output power density by minimizing eddy current loss and copper loss, while maintaining high torque and reducing magnetic saturation, thus improving the energy efficiency of electric motors.
Implementation Method 1
an eddy current is generated in a coil of an electric motor by a magnetic flux from a rotor
Implementation Method 2
an eddy current is generated in a coil of an electric motor by a magnetic flux from a rotor. When a flat-square coil is used for this coil, the eddy current loss is likely to increase due to the increase in the surface area
Data Source
AI summary
A stator includes: a stator core (11) including a back yoke (13) provided around an axis and surrounding a rotor (30), and teeth (14) provided at intervals in a circumferential direction of the axis and attached to the back yoke (13), and a coil (12) wound around each of the teeth (14). Each of the teeth (14) has an inner circumferential surface facing the rotor (30) and includes a tip portion (14a) projecting forward and backward in a rotational direction of the rotor (30), and a base portion (14b) facing the back yoke (13). The inner circumferential surface (14c) includes a first region (14d) and a second region (14e). An average interval between the second region (14e) and an outermost locus of the rotor (30) is larger than an average interval between the first region (14d) and the outermost locus of the rotor (30).