Offset Propulsion Motor Layout for Linear Force Ripple Reduction
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Solution Overview
Problem
Existing transportation systems face challenges in achieving high speed, high efficiency, and high-power density while propelling a payload and/or vehicle along a track using a propulsion motor, and guiding and levitating the motor relative to the track.
Innovation Solution
The system employs homopolar linear synchronous motors with ferromagnetic cores shaped to provide increasing magnetic permeance or decreasing magnetic reluctance from the ends towards the center, along with stepped armature coils and strategically designed track segments to reduce force ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional propulsion motors are used to propel the vehicle along the track, then the basic propulsion function is achieved, but force ripple occurs that reduces propulsion efficiency and prevents high-speed operation
Solution Approach 1:
The ferromagnetic cores are designed with non-uniform cross-sectional areas along their length, creating local variations in magnetic permeance. Specifically, the end cores have smaller cross-sectional areas than the intermediate cores, which locally modifies the magnetic flux distribution and reduces force ripple at the ends of the motor where it is most problematic.
Solution Approach 2:
The propulsion motor employs an asymmetric configuration where the end ferromagnetic cores differ from the intermediate cores in terms of cross-sectional area. This asymmetric design breaks the symmetry that would otherwise cause equal force ripple at both ends, allowing for optimized magnetic flux paths that reduce overall force ripple and enable high-speed operation.
2Speed
If the vehicle operates at high speed, then transportation efficiency is improved, but force ripple increases which limits the achievable speed and stability
Solution Approach 1:
The magnetic circuit parameters are changed by varying the cross-sectional areas of the ferromagnetic cores along their length. The end cores have reduced cross-sectional areas compared to intermediate cores, which changes the magnetic reluctance and flux distribution parameters to reduce force ripple and improve force stability at high speeds.
3Ease of manufacture
If uniform ferromagnetic cores are used in the propulsion motor, then manufacturing is simplified, but force ripple is maximized reducing propulsion performance
Solution Approach 1:
Rather than using uniform cores throughout, the design applies local quality variations where only the end cores have reduced cross-sectional areas. This targeted approach minimizes the manufacturing complexity increase while effectively reducing force ripple at the critical end regions where magnetic flux discontinuities cause the most harm.
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 enhances propulsion efficiency, reduces force ripple, and improves power density, enabling high-speed and high-efficiency operation of the transportation system.
Implementation Method 1
the one or more end ferromagnetic cores shaped to provide one or more of increasing magnetic permeance or decreasing magnetic reluctance from the end of the movement axis towards a center of the propulsion motor
Implementation Method 2
armature coils to induce a varying second magnetic flux in the at least one ferromagnetic core perpendicular to the magnetic flux pathway, thereby inducing a propulsion force perpendicular to the magnetic flux pathway
Data Source
AI summary
A vehicle with offset propulsion motors is provided. The vehicle comprises: a body; and a plurality of propulsion motors at a side of the body, arranged in a line about parallel to a movement axis of the body. Displacements between adjacent propulsion motors along the movement axis are selected according to an electrical period of poles of the plurality of propulsion motors, and an offset distance. The offset distance is determined by dividing the electrical period into the offset distance to determine a remainder. The electrical period divided by the remainder is about equal to a number of the plurality of propulsion motors divided by a given integer value that is less than the number of the plurality of propulsion motors, and produces a largest common divider between the given integer value and the number of the plurality of propulsion motors of “1”.