D-Shaped Permanent Magnet for AC Servo Motor Torque Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Permanent magnet rotating machines, such as AC servo motors, face issues with cogging torque and demagnetization due to the alignment of stator slots and permanent magnets, leading to torque ripples and reduced drive torque, which affect controllability and noise.
Innovation Solution
A D-shaped permanent magnet with a generally arcuate top surface, a flat bottom surface, and side surfaces is designed, where the central region is off-centered and the transversely opposed end regions are kept relatively thick to minimize cogging torque and prevent demagnetization, achieved by arranging multiple magnets with specific dimensions and configurations to reduce magnetic flux variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the permanent magnet segment is configured to a D shape with off-centered arcuate portion to reduce cogging torque, then the cogging torque is reduced, but the end portions become very thin and susceptible to demagnetization
Solution Approach 1:
The patent applies local quality by differentiating the thickness of the permanent magnet segment across its structure. The central portion maintains a first thickness optimized for reducing cogging torque through off-centering, while the end portions maintain a greater second thickness to prevent demagnetization. This localized variation in geometric property allows each region to fulfill its specific functional requirement independently.
Solution Approach 2:
The patent employs asymmetry by configuring the permanent magnet segment with a D-shaped cross-section featuring an off-centered arcuate portion. The segment is asymmetric about the radial direction, with the arcuate portion offset from the center by a specific distance. This asymmetric configuration smoothes the magnetic flux distribution at the magnetic pole switch area, effectively reducing cogging torque while the thickness variation provides structural reinforcement where needed.
2Productivity
If the permanent magnet segment is made thinner at end portions to reduce volume and improve torque density, then the drive torque per volume increases, but the susceptibility to demagnetization increases
Solution Approach 1:
The patent applies local quality by differentiating the thickness of the permanent magnet segment across its structure. The central portion maintains a first thickness optimized for reducing cogging torque through off-centering, while the end portions maintain a greater second thickness to prevent demagnetization. This localized variation in geometric property allows each region to fulfill its specific functional requirement independently.
3Ease of manufacture
If the permanent magnet segment is configured with uniform thickness to simplify manufacturing, then the manufacturing complexity is reduced, but the cogging torque cannot be effectively reduced
Solution Approach 1:
The patent employs asymmetry by configuring the permanent magnet segment with a D-shaped cross-section featuring an off-centered arcuate portion. The segment is asymmetric about the radial direction, with the arcuate portion offset from the center by a specific distance. This asymmetric configuration smoothes the magnetic flux distribution at the magnetic pole switch area, effectively reducing cogging torque while the thickness variation provides structural reinforcement where needed.
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
The D-shaped magnet effectively reduces cogging torque, increases drive torque, and prevents demagnetization, enhancing the performance and precision control of AC servo and DC brushless motors, while maintaining high output and reducing size.
Implementation Method 1
magnetic orientation is effected in a parallel magnetic field so that a direction of easy magnetization is parallel to the center axis of the magnet segment
Implementation Method 2
The magnitude of demagnetization of a permanent magnet is determined by the magnitude of a coercive force and the magnitude of a diamagnetic field at the service temperature
Implementation Method 3
The self diamagnetic field increases as the thickness of the permanent magnet in the magnetization direction is reduced
Data Source
AI summary
A permanent magnet has a D-shaped cross section including an arcuate top surface (22), a flat bottom surface (24), and side surfaces (26, 28). Provided that a plurality of permanent magnets are circumferentially arranged so that a great circle (S) circumscribes the apexes (P) on the arcuate top surfaces (22), the top surface (22) includes a central region which delineates an arc of a small circle (T) off-centered from the great circle, and end regions (22a, 22b) which are positioned outside the small circle (T) and inside the great circle (S).