Rectangular Stranded Coil Winding via Face-wise Bending
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Solution Overview
Problem
Traditional coil winding techniques for electric machines, particularly those using rectangular Litz coils, face challenges with edge-wise bends that can cause damage and increase AC losses due to slot leakage and proximity effects.
Innovation Solution
The technique involves winding rectangular stranded wire coils, such as Litz coils, with wider face-wise bends instead of traditional edge-wise bends, utilizing a configuration where the planar surfaces of the coils are oriented in the radial direction of the slots to minimize AC losses and facilitate easy manufacturing without damaging pre-insulated turns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional edge-wise bending technique is used to wind rectangular coils, then the wide faces can be perpendicular to the radial direction to minimize AC losses, but the conductor suffers damage and manufacturing becomes difficult
Solution Approach 1:
The patent inverts the traditional bending approach by bending the wide faces of the rectangular conductor instead of the narrow edges. This reversal of the bending orientation allows the conductor to be formed into coil turns without the difficulty and damage associated with edge-wise bending, while still achieving the desired orientation of wide faces perpendicular to the radial direction for minimizing AC losses.
2Reliability
If pre-insulated conductors are used to protect the conductor, then damage during winding is reduced, but the insulation is damaged by traditional edge-wise bends
Solution Approach 1:
By inverting the bending orientation from edge-wise to face-wise, the patent eliminates the concentration of stress on the insulation at the narrow edges. The broader distribution of bending stress across the wide face of the rectangular conductor prevents insulation damage, allowing pre-insulated conductors to be successfully wound into coils.
3Loss of energy
If rectangular Litz wire is used to reduce AC losses from eddy currents, then proximity effects are reduced, but the wire is damaged by traditional edge-wise bends
Solution Approach 1:
The patent applies face-wise bending instead of edge-wise bending to rectangular Litz wire coils. This inversion of the bending approach preserves the integrity of the Litz wire construction by avoiding the stress concentration at the narrow edges that would damage the individual strands and their insulation, while still achieving the orientation needed to minimize eddy current and proximity effect losses.
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 approach reduces AC losses from eddy and circulating currents, radial fringe fields, and proximity effects within the slots, enabling the production of high-performance electric machines with low manufacturing costs and maintaining dielectric integrity.
Implementation Method 1
The skin effect power losses associated with high frequency applications are therefore reduced
Implementation Method 2
Litz wire is used to make inductors and transformers for high frequency applications where the skin effect is more pronounced and proximity effect can be an even more severe problem
Implementation Method 3
Rectangular coils such as field winding coils for electric machines are traditionally wound with the planar surface of the wider faces perpendicular to the orientation or radial direction of the coil slots in order to minimize AC losses associated with slot leakage
Data Source
Figure 1~2
Figure 3~4
AI summary
A technique for winding multi-turn, stranded wire coils (10) using rectangular cables (12) avoids the risk of damage associated with edge-wise bends (48).