Stator Magnet Segmentation in Rotary Electric Machines
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Solution Overview
Problem
In rotary electric machines with permanent magnets on the stator side, eddy current losses are significant due to the lack of effective methods to divide and arrange permanent magnets to reduce these losses efficiently.
Innovation Solution
The rotary electric machine design features a stator with a cylindrical stator core and teeth, where permanent magnets are arranged with the same magnetic poles in the circumferential direction and extend in the protruding direction of the teeth, and a groove portion is formed along the shaft direction to divide the eddy current path, reducing the magnitude of the eddy current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a permanent magnet is provided on the stator side to achieve higher output power and operational speed, then the machine can meet downsizing and performance demands, but a great amount of eddy current loss is caused due to the stationary magnet interacting with the revolving magnetic field
Solution Approach 1:
The permanent magnet is divided into multiple magnet pieces arranged in the circumferential direction. This segmentation breaks the continuous eddy current path into smaller segments, reducing the magnitude of eddy currents and consequently decreasing eddy current losses while maintaining the magnetic field strength required for high output power
Solution Approach 2:
Groove portions are introduced at specific locations on the permanent magnet (at the circumferential direction ends and/or intermediate positions). These grooves create local non-conductive regions that interrupt eddy current paths, reducing energy losses in critical areas where eddy currents are most intense, while preserving the overall magnetic performance
2Loss of energy
If a bond magnet with low electric conductivity is used to reduce eddy current loss, then eddy current can be reduced, but the output power of the rotary electric machine falls since the bond magnet is inferior to a sintered magnet in magnetic force
Solution Approach 1:
By dividing the permanent magnet into multiple pieces, the patent reduces eddy current losses without requiring low-conductivity bond magnet materials. The segmentation itself provides the eddy current interruption, allowing the use of high-magnetic-force sintered magnets while avoiding the output power penalty associated with bond magnets
Solution Approach 2:
The groove portions act as intermediary non-conductive elements that interrupt eddy current paths. These grooves provide the necessary electrical isolation without requiring the entire magnet to be made of low-conductivity material, thus preserving the high magnetic force properties of sintered magnets while achieving eddy current reduction
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 eddy current losses by dividing the eddy current path and minimizing its magnitude, enhancing the machine's efficiency and torque production.
Implementation Method 1
The magnetic flux interlinkages with a permanent magnet, and an eddy current flows in the permanent magnet, so that variations of the magnetic flux can be cancelled out. Thereby, an eddy current loss is caused.
Implementation Method 2
a groove portion extending in a shaft direction of the rotor is formed on a surface along both a protruding direction of the teeth of the permanent magnet and the shaft direction of the rotor
Data Source
AI summary
An object is to obtain a rotary electric machine, capable of reducing an eddy current loss which is caused in a magnet member provided in a stator. A rotor and a stator which is arranged to face to the rotor in a radial direction of the rotor are provided. The stator has a stator core, a stator coil, and a magnet member. The stator core has a core back and teethes, and the teethes protrude from the core back toward the rotor and are arranged along a circumferential direction. The stator coil is wound to each of the plurality of teethes, and is arranged in a slot formed between teethes lying next to each other in the circumferential direction. The magnet member is formed of a plurality of permanent magnets in each of the teethes.