Rotor Void Positioning for Torque and Cooling
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Solution Overview
Problem
The existing rotor design in rotating electric machines with a void portion located on a straight line connecting the inner-peripheral-side ends of magnets obstructs magnetic flux, reducing motor torque and efficiency due to increased core loss and potential demagnetization from excessive heating.
Innovation Solution
The void portion is positioned on the inner peripheral side of an imaginary line connecting the inner-peripheral-side corners of the magnets, with a second width smaller than the first width, allowing for minimal obstruction of magnetic flux while maintaining effective cooling, by ensuring the void portion is as close as possible to the magnets without impeding the magnetic flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the void portion is located on a straight line connecting between inner-peripheral-side end portions of the pair of magnets, then the cooling performance for the magnets is improved, but the passage of magnet magnetic flux is obstructed reducing motor torque and efficiency
Solution Approach 1:
The patent transitions from a one-dimensional straight-line positioning to a two-dimensional spatial positioning defined by an imaginary arc. The void portion is positioned on an imaginary arc connecting inner-peripheral-side corners of the magnets rather than a straight line, utilizing curvature to achieve both cooling effectiveness and magnetic flux passage. This dimensional change in the positioning geometry resolves the contradiction by allowing the void to remain close to magnets for cooling while avoiding direct obstruction of flux paths.
Solution Approach 2:
The patent applies different positioning criteria for different regions: the void portion is specifically positioned on an imaginary arc rather than a straight line, creating a localized geometric modification. This local quality change in the void positioning allows the system to maintain optimal cooling performance in the magnet region while preserving magnetic flux passage in the space between magnets, thereby resolving the torque reduction issue.
2Temperature
If the void portion is located on a straight line connecting between inner-peripheral-side end portions of the pair of magnets, then the cooling performance is improved, but the core loss increases due to increased density of magnetic flux
Solution Approach 1:
By positioning the void on an imaginary arc rather than a straight line, the patent creates a curved spatial relationship that maintains proximity to magnets for effective cooling while distributing magnetic flux more evenly. This arc-based positioning prevents flux concentration that would occur with straight-line positioning, thereby reducing core loss without sacrificing cooling performance.
3Power
If the void portion is located far from the magnets, then the obstruction to magnet magnetic flux passage is eliminated, but the cooling performance deteriorates causing demagnetization
Solution Approach 1:
The patent uses an imaginary arc as the positioning reference, which naturally curves toward the magnets. This allows the void to be positioned closer to the magnets than a straight-line approach would permit, maintaining effective cooling while the arc geometry ensures the void does not directly block flux paths, thus preserving motor torque.
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 motor torque and efficiency by allowing unobstructed magnetic flux passage and effective cooling, reducing the risk of demagnetization and core loss, while maintaining a suitable cross-sectional area for flux passage.
Implementation Method 1
performance for cooling the magnets
Implementation Method 2
a pair of magnets disposed on respective opposite sides of the q-axis are arranged to form an inverted-V shape... almost no magnetic field line passes on the inner peripheral side
Data Source
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AI summary
A rotor (12) to be provided in a rotating electric machine (10). The rotor (12) includes a rotor core (22) provided with a pair of flux barriers (40c, 40d) and a void portion (42). A pair of magnets (b, c) are provided in the pair of flux barriers (40c, 40d). Each of the pair of magnets (b, c) has a rectangular shape in its cross section. The void portion (42) is located on an inner peripheral side than an imaginary line (Lm) connecting between inner-peripheral-side corners (bi, ci) of the pair of magnets (b, c). A first width (Wql) is defined by a shortest distance between the pair of flux barriers (40c, 40d). A second width (Wq2) is defined by a distance from the void portion (42) to an intersection point (P) at which the imaginary line (Lm) intersects with a shortest line segment (Ls) whose length corresponds to a shortest distance between one of the pair of magnets (b, c) and the void portion (42). The second width (Wq2) is smaller than the first width (Wql).