Variable Cross Section Stator Windings for Electric Machines
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Solution Overview
Problem
Electric machines with high winding density face challenges in manufacturing complexity and copper losses due to the skin effect, particularly at high speeds, where only the outer surface of conductors effectively conduct current, leading to inefficiencies and increased manufacturing costs.
Innovation Solution
The design incorporates stator windings with at least two different cross-sectional areas, where smaller conductors are positioned closer to the rotor and larger conductors radially outward, reducing copper losses while maintaining manufacturing efficiency by minimizing the number of welds required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the cross sectional size of hairpin conductors is increased to reduce the number of conductors and welds, then manufacturing complexity is reduced, but copper losses increase due to the skin effect at high speeds
Solution Approach 1:
The stator windings are segmented into multiple conductors with different cross-sectional areas. Specifically, first windings have a first cross-sectional area while second windings have a second cross-sectional area that is smaller than the first. This segmentation allows the system to use fewer, larger conductors in positions where the skin effect is less problematic, while using smaller conductors where the skin effect is more significant, thereby balancing manufacturing simplicity with electrical efficiency.
Solution Approach 2:
Different regions of the stator windings are assigned different conductor cross-sectional areas based on their specific operational characteristics. The first windings with larger cross-sectional areas are placed in positions where they can effectively carry current with minimal skin effect impact, while second windings with smaller cross-sectional areas are placed in positions where the skin effect would otherwise cause excessive copper losses. This local differentiation optimizes both manufacturing and electrical performance.
2Device complexity
If the cross sectional size of conductors is increased, then the number of welds is reduced, but the effectiveness of copper material decreases due to the skin effect
Solution Approach 1:
The winding system is divided into first and second windings with different cross-sectional areas. This segmentation enables the use of larger conductors (fewer welds) in positions where they are most effective, while using smaller conductors in positions where the skin effect would otherwise render the copper material ineffective. The result is an optimized balance between reducing weld complexity and maintaining copper material effectiveness.
Solution Approach 2:
The cross-sectional area parameter of the conductors is varied across different windings rather than using a uniform size. By changing this physical parameter, the system achieves fewer welds overall while ensuring that copper material is effectively utilized in all positions, as smaller conductors are placed where the skin effect would otherwise cause the center portion to be electrically inactive.
3Productivity
If high winding density is achieved using hairpin conductors, then efficiency is improved, but manufacturing complexity and copper losses increase
Solution Approach 1:
The high-density winding structure is achieved through segmentation into first and second windings with different cross-sectional areas. This segmentation maintains the high slot fill factor and efficiency benefits of dense windings while reducing manufacturing complexity by using fewer, strategically sized conductors rather than many small, uniformly sized conductors that would require extensive welding and assembly.
Solution Approach 2:
Different conductor sizes are applied to different winding positions based on local electrical and mechanical requirements. This local quality approach maintains high winding density and efficiency where needed while simplifying manufacturing in positions where larger conductors reduce the number of welds and assembly steps required.
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 copper losses and manufacturing complexity, achieving a balance between efficiency and cost-effectiveness by optimizing the distribution of conductive material within the stator slots, especially at high rotational speeds.
Implementation Method 1
the conductors are subjected to what is commonly referred to as the skin effect with only that portion of the conductor near the outer surface of the conductor conducting electrical current
Data Source
AI summary
An electric machine including a rotor operably coupled with a stator having a plurality of stator windings. Each stator winding defines has a plurality of axially extending segments disposed within the stator slots and a plurality of end turn segments. At least one first axially extending segment defining a first cross sectional area and at least two second axially extending segments defining a smaller second cross sectional area are disposed in each of the stator slots. At least one of the plurality of end turn segments conductively couples a single first axially extending segment in a first one of the plurality of slots to at least two second axially extending segments in a second one of the plurality of slots. In some embodiments, the larger first axially extending segments are all disposed radially outwardly of the smaller second axially extending segments. The windings may be formed using hairpin conductors.