Axial Flux Motor Pole Layout for Lower Cogging Torque
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Solution Overview
Problem
Electric axial flux machines suffer from pole sensitivity, leading to unsteady running due to varying magnetic resistance and driving force, which is not effectively addressed by existing solutions that reduce torque by altering permanent magnet distribution.
Innovation Solution
An electric axial flux machine design with a disc-shaped rotor featuring magnetic poles arranged with alternating pole widths and identical pole pitch, allowing for small stator pole distances without significantly affecting torque, using permanent magnets and Somaloy materials for improved efficiency and robustness, and cuboid magnets for cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If permanent magnets are separated by different distances in the circumferential direction to reduce pole sensitivity, then pole sensitivity is reduced, but the occupancy of the rotor with permanent magnets is reduced and torque is reduced
Solution Approach 1:
The patent applies local quality by differentiating the widths of adjacent magnetic poles (first pole width vs. second pole width) while maintaining uniform pole pitch. This local variation in pole geometry reduces pole sensitivity without requiring non-uniform spacing, thereby avoiding the torque reduction that would result from reduced magnet occupancy.
Solution Approach 2:
The invention introduces asymmetry in the magnetic pole structure by alternating between wider and narrower poles around the rotor circumference. This asymmetric design breaks the symmetry that causes cogging torque, reducing pole sensitivity while maintaining high torque through optimized magnet placement and uniform pole pitch.
2Productivity
If the rotor is designed with compact dimensions in the axial direction to achieve high power density, then axial dimensions are reduced and power density increases, but pole sensitivity management becomes more challenging
Solution Approach 1:
The patent addresses pole sensitivity in compact axial designs by changing the geometric parameters of magnetic poles - specifically alternating pole widths while maintaining uniform pole pitch. This parameter optimization allows effective pole sensitivity management within the constrained axial space of high-power-density motors.
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
Significantly reduces pole sensitivity and maintains high torque, enabling precise and stable operation, suitable for collaborative robots and other applications requiring high precision and reduced manufacturing costs.
Implementation Method 1
The magnetic flux of the electric axial flux machine is arranged in the axial direction
Implementation Method 2
During operation of the electric axial flux machine, the relative movement of teeth and magnetic poles results in the fact that a tooth or a groove base arranged between two teeth is alternately arranged opposite a magnetic pole
Implementation Method 3
The magnetic resistance and thus the driving force of the electric axial flux machine varies, which leads to unsteady running. This is known to those skilled in the art as pole sensitivity, cogging torque or cogging
Data Source
AI summary
An electric axial flux machine having a disc-shaped rotor with a main part and P magnetic poles, which are arranged along the circumferential direction of the main part in a mutually spaced manner by an identical pole pitch and having a disc-shaped stator with Z teeth, wherein the P magnetic poles are arranged along the circumferential direction so as to have a first pole width and a second pole width in an alternating manner. The disclosure additionally relates to a collaborative robot.