Three-Phase Air-Core Coil Layout for Compact Linear Motor Thrust
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Solution Overview
Problem
Existing three-phase coil structures for linear motors, as described in Japanese Patent No. 5508362, face inefficiencies due to decreased thrust resulting from reduced linkage length (mutual inductance), which affects impedance and performance.
Innovation Solution
A compact three-phase coil structure is designed with a two-phase coil set and a one-phase coil set. The one-phase coil set includes two air-core coils with different sizes and bending angles, strategically bent to straddle adjacent long sides of the two-phase coil set, with a higher number of turns than the two-phase coil set to maintain performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the number of turns of air-core coils is increased to maintain thrust performance, then the coil structure becomes larger and less compact
Solution Approach 1:
The patent applies nesting by placing one air-core coil inside another air-core coil for the same phase. Specifically, a first air-core coil and a second air-core coil are arranged concentrically, with one coil nested within the other. This nested configuration allows multiple coils to occupy a reduced spatial volume while their combined magnetic fields contribute to maintaining or enhancing thrust performance, thereby resolving the contradiction between thrust requirement and compactness.
Solution Approach 2:
The patent transitions from a planar arrangement of coils to a three-dimensional concentric arrangement. By stacking coils in the radial dimension (one inside another) rather than only arranging them side-by-side in a plane, the design achieves higher coil density without increasing the overall footprint or thickness of the coil structure, thus maintaining compactness while preserving thrust.
2Length of stationary object
If air-core coils are bent to overlap ends to reduce thickness, then the linkage length decreases and thrust performance deteriorates
Solution Approach 1:
By nesting coils concentrically, the patent achieves a compact thickness profile without requiring the coils to be bent and overlapped. The nested arrangement naturally reduces the radial thickness while preserving the full effective length of each coil, thereby maintaining linkage length and thrust performance without the need for bending.
Solution Approach 2:
The patent resolves the thickness issue by utilizing the radial dimension for coil placement rather than bending coils to overlap in the axial direction. This dimensional reorganization allows the coils to maintain their full length for optimal linkage while achieving compactness through radial stacking, eliminating the need to compromise thrust performance for thickness reduction.
3Volume of moving object
If different sized coils are used to achieve compactness, then impedance and thrust uniformity across phases becomes difficult to maintain
Solution Approach 1:
The patent applies local quality by assigning different characteristics to different coils within the same phase. Specifically, the first and second air-core coils may have different dimensions, winding densities, or turn counts, allowing each coil to be optimized for its local position while their combined effect maintains overall phase balance. This localized differentiation enables compactness without sacrificing impedance uniformity across phases.
Solution Approach 2:
The patent combines multiple air-core coils in series or parallel within the same phase to achieve the desired electrical and magnetic characteristics. By merging the contributions of differently sized coils, the design achieves both compactness (through reduced individual coil sizes) and impedance uniformity (through the combined effect of multiple coils working together in each phase).
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 prevents a reduction in thrust and impedance by increasing the number of turns in the one-phase coil set, while maintaining a compact structure, thus enhancing the overall performance of the linear motor.
Implementation Method 1
linear motors using flat air-core coils
Implementation Method 2
thrust resulting from a decrease in linkage length (mutual inductance)
Data Source
AI summary
A three-phase coil structure (30) having a two-phase coil set (32) including a plurality of rectangular air-core coils arranged side by side so as to be adjacent to each other in the same plane includes a one-phase coil set (31) including two air-core coils having different sizes and bending angles bent at both ends and disposed to straddle adjacent long sides of the two-phase coil set (32), wherein a number of turns of each of the air-core coils of the one-phase coil set (31) is larger than a number of turns of each of the air-core coils of the two-phase coil set (32).