Segmented Stator Magnet Layout for Lower Eddy Current Loss
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Solution Overview
Problem
In rotary electric machines, the use of rare earth sintered magnets in stators leads to eddy current loss and thermal demagnetization due to magnetic flux interlinkage, resulting in performance deterioration and reduced efficiency.
Innovation Solution
The stator design includes a stator core with divided stator magnets along the circumferential direction of the slots, and magnetic chip portions on the wall surfaces between the stator coil and magnet, which are spaced apart to reduce eddy current loss and magnetic saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a rare earth sintered magnet is used as the stator magnet to increase output, then the magnetic force and power output are improved, but eddy current loss occurs in the stator magnet due to magnetic flux interlinkage, causing performance deterioration and efficiency reduction
Solution Approach 1:
The stator magnet is divided into multiple segments along the circumferential direction of the stator slot. This segmentation interrupts the continuous magnetic flux path that causes eddy currents, thereby reducing eddy current loss while maintaining the overall magnetic output of the stator magnet assembly.
Solution Approach 2:
Magnetic chip portions are introduced as intermediary elements between the stator coil and the stator magnet. These magnetic chips are spaced apart to create magnetic flux paths that reduce direct flux interlinkage with the stator magnet, thereby suppressing eddy current generation while maintaining magnetic coupling for power output.
2Power
If the stator magnet operates at high magnetic flux density to improve performance, then the power generation capability is enhanced, but Joule heat is generated by eddy currents, causing temperature rise and thermal demagnetization
Solution Approach 1:
Dividing the stator magnet into segments reduces the area available for eddy current circulation, thereby reducing Joule heat generation from eddy currents. This allows the stator magnet to operate at high magnetic flux density for improved power generation without excessive temperature rise that would cause thermal demagnetization.
Solution Approach 2:
The spaced-apart magnetic chip portions act as intermediaries that modify the magnetic flux distribution, reducing direct flux penetration into the stator magnet body. This reduces eddy current-induced Joule heating while maintaining sufficient magnetic coupling for power generation, thereby controlling temperature rise and preventing thermal demagnetization.
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 design effectively suppresses eddy current loss and thermal demagnetization, maintaining performance and reliability by minimizing magnetic flux leakage and saturation, thereby enhancing the output of the rotary electric machine.
Implementation Method 1
when a rare earth sintered magnet is used as the stator magnet, if a magnetic flux generated from the rotor interlinks with the stator magnet, an eddy current is generated on the surface, of the stator magnet, on the side opposed to the rotor
Implementation Method 2
a magnetic flux generated from the rotor interlinks with the stator magnet
Implementation Method 3
both speed change and power generation are possible with one rotary electric machine
Implementation Method 4
when an eddy current is generated in the stator magnet, Joule heat is generated in the stator magnet by the eddy current
Implementation Method 5
if the temperature of the permanent magnet exceeds the permissible temperature, the permanent magnet is thermally demagnetized, thus causing a problem that the performance of the stator deteriorates due to the decrease in the magnetic force of the permanent magnet
Data Source
AI summary
A stator includes: a stator core including a plurality of stator teeth in a circumferential direction with respect to a center of rotation of a rotary electric machine; a stator coil disposed on a bottom portion side of each of a plurality of stator slots formed between the stator teeth; and a stator magnet disposed on an opening side of each of the plurality of stator slots and having the same polarity in a radial direction, and in each of the stator slots, the stator magnet is divided at a center in the circumferential direction of the stator slot.