Interior Permanent Magnet Motor Slot Geometry for Demagnetization Resistance
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Solution Overview
Problem
In interior permanent magnet motors, arc-shaped permanent magnets can move inside magnet insertion holes due to electromagnetic forces, making it difficult to secure air gaps that prevent demagnetization, and reducing magnetic resistance by narrowing the magnet insertion hole to restrict movement results in reduced demagnetization suppression effectiveness.
Innovation Solution
The motor design includes arc-shaped permanent magnets and magnet insertion holes with straight surfaces orthogonal to the magnetic pole center line, ensuring contact between these surfaces to restrict magnet movement without relying on abutment portions, and varying air gaps to enhance magnetic resistance and demagnetization resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the width of the magnet insertion hole is reduced to restrict permanent magnet movement, then the permanent magnet movement is restricted, but the magnetic resistance is reduced which weakens the demagnetization suppression effectiveness
Solution Approach 1:
The invention transitions from controlling magnet position through horizontal width constraints to vertical depth constraints. By forming the radially-inner insertion hole contour surface with a straight surface that extends in the radial direction, the patent restricts magnet movement along the arc-shaped insertion hole path without reducing the magnet insertion hole width, thereby maintaining both magnetic resistance and demagnetization suppression effectiveness.
Solution Approach 2:
The invention applies a localized straight surface configuration specifically to the radially-inner insertion hole contour surface where magnet movement occurs during operation. This localized modification creates frictional contact that restricts magnet movement along the insertion hole, while leaving other regions of the insertion hole maintaining their original arc shape to preserve magnetic flux paths and resistance.
2Stability of the object's composition
If abutment portions are formed by making the magnet insertion hole narrower than the permanent magnet width, then the permanent magnet movement is restricted through contact, but the air gap portions are reduced which weakens demagnetization suppression
Solution Approach 1:
The invention eliminates the need for abutment portions by transitioning from horizontal width-based position control to vertical depth-based position control. The straight surface on the radially-inner insertion hole contour surface creates frictional contact that restricts magnet movement without requiring the insertion hole to be narrower than the magnet width, thereby preserving the air gap portions and their demagnetization suppression function.
3Reliability
If air gap portions are secured between the magnet insertion hole and permanent magnet side end surfaces, then demagnetization is suppressed, but the permanent magnet can move inside the insertion hole due to electromagnetic forces
Solution Approach 1:
The invention introduces a straight surface configuration localized to the radially-inner insertion hole contour surface to provide frictional contact that restricts magnet movement. This localized structural modification works in conjunction with the air gap portions, allowing both functions—position stability and demagnetization suppression—to coexist without interference.
Solution Approach 2:
The straight surface acts as an intermediary mechanism that provides frictional contact between the insertion hole and permanent magnet. This intermediary contact restricts magnet movement along the insertion hole path while maintaining the air gap portions that suppress demagnetization, resolving the contradiction between position stability and demagnetization protection.
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 restricts permanent magnet movement and enhances demagnetization resistance, maintaining magnetic efficiency and compactness while preventing demagnetization, even under high-load conditions.
Implementation Method 1
at least one straight surface configured to suppress movement of the permanent magnet along the magnet insertion hole having the arc shape
Implementation Method 2
air gap portions are formed between the side-end magnet contour surfaces and the side-end insertion hole contour surfaces... the width of the magnet insertion hole is reduced so that the magnetic resistance is reduced
Implementation Method 3
the permanent magnet may be moved inside the magnet insertion hole due to an electromagnetic force generated during the drive of the motor
Implementation Method 4
When a large current flows through the stator to apply a demagnetizing field to the rotor, the side end surfaces of the permanent magnet are most easily demagnetized
Data Source
Figure 1
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AI summary
In an interior permanent magnet motor (1), each of permanent magnets (19) has a radially-inner magnet contour surface (43), a radially-outer magnet contour surface (45), and a pair of side-end magnet contour surfaces (47). Each of magnet insertion holes (21) has a radially-inner insertion hole contour surface (53), a radially-outer insertion hole contour surface (55), and a pair of side-end insertion hole contour surfaces (57). The radially-outer magnet contour surface and the radially-outer insertion hole contour surface are each formed by a first arc surface. The radially-inner magnet contour surface and the radially-inner insertion hole contour surface are each formed by a second arc surface and at least one straight surface configured to suppress movement of the permanent magnet along the magnet insertion hole having an arc shape.