Split Core Groove Mitigates Compression Stress
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Solution Overview
Problem
Rotating electrical machines with split cores experience compression stress and local stress concentration due to shrink fit or press fit, leading to increased iron loss and efficiency decrease, as well as potential bending and separation of steel sheets at the end portions.
Innovation Solution
A rotating electrical machine design featuring a groove on the outer peripheral surface of the split core with a trapezoid-shaped first protrusion, inclined side surfaces, and acute-angled notches that absorb and mitigate compression stresses, preventing local stress concentration and steel sheet separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If shrink fit or press fit is applied to the split cores on the frame, then the split cores are securely fixed to the frame, but large compression stress occurs on the split cores leading to increased iron loss and decreased efficiency
Solution Approach 1:
The groove is introduced at a specific location (outer peripheral surface of the split core) to locally relieve compression stress. This creates a non-uniform stress distribution that prevents excessive stress concentration in critical areas, thereby reducing iron loss while maintaining overall fixing strength through the remaining contact areas.
2Stress or pressure
If a second notch is disposed on the base surface of the first notch to mitigate compression stress, then compression stress is reduced, but local stress concentration occurs at the second notch position obstructing magnetic flux
Solution Approach 1:
The harmful second notch that causes local stress concentration is removed from the design. Instead, only a groove (first notch) is provided on the outer peripheral surface, which relieves compression stress without creating stress concentration points that would obstruct magnetic flux passage through the yoke.
3Strength
If compression force from the frame increases toward the end portion in the lamination direction, then the split core is firmly secured, but steel sheets may bend and separate from the split core at the end portion
Solution Approach 1:
The groove is positioned to provide local stress relief specifically in areas prone to steel sheet separation. This creates a stress distribution pattern that prevents bending and separation of steel sheets at the end portions while maintaining firm securing through the overall compression force distribution.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
[PROBLEM TO BE SOLVED] To allow for mitigating compression stress occurring on split cores and suppressing occurrence of local stress concentration, even when a large compression force acts on the outer peripheral of the stator core of a rotating electrical machine from a frame. [SOLUTION] The rotating electrical machine 1 includes a frame 4, and a stator core 5 fixed to an inner peripheral surface of the frame 4 and including a plurality of split cores 20 disposed in a peripheral direction. Each of the plurality of split cores 20 includes a groove 30 disposed along an axial direction on a central position in the peripheral direction on the outer peripheral surface of the split core 20, and a first protrusion 32 disposed on a bottom 31 of the groove 30 and protruding outward in a radial direction.