BLDC Motor Permanent Magnet Geometry for Torque Ripple Reduction
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Solution Overview
Problem
High-quality permanent magnets in BLDC motors increase manufacturing costs and lead to reduced efficiency and operation performance due to increased core loss, magnetic dead zones, cogging torque, and total harmonic distortion (THD) of counter electromotive force.
Innovation Solution
The BLDC motor features permanent magnets with an arched section where the outer circumference is extended in both directions from the rotation center, with a narrower width at the ends and a thicker middle part, optimizing magnetic flux distribution to reduce torque ripple and THD, and configured to maximize the magnetic path to the stator, adhering to specific width and height ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If permanent magnets of high quality material are used to increase effective magnetic flux, then effective magnetic flux is improved, but manufacturing cost increases due to increased rare earth material content
Solution Approach 1:
The permanent magnet is designed with non-uniform thickness, being thicker at the rotation center side and thinner at the outer circumference side. This local variation in geometry optimizes the magnetic flux distribution, allowing effective magnetic flux to be increased without requiring higher quality (more expensive) magnetic materials throughout the entire magnet structure.
2Quantity of substance
If the overall thickness of permanent magnets is increased to increase effective magnetic flux, then effective magnetic flux is improved, but core loss increases due to reduced magnetic path to stator
Solution Approach 1:
The permanent magnet thickness is varied locally, being thicker at the rotation center side where it is needed for effective magnetic flux, and thinner at the outer circumference side where excessive thickness would create magnetic dead zones and increase core loss. This local optimization maintains adequate magnetic path length to the stator while preserving effective flux.
Solution Approach 2:
Instead of uniformly increasing magnet thickness in the radial direction, the invention introduces a dimensional variation by making the magnet thicker at the rotation center side and thinner at the outer circumference side. This dimensional change optimizes both effective magnetic flux and magnetic path length to stator, reducing core loss while maintaining flux levels.
3Quantity of substance
If the overall thickness of permanent magnets is increased to increase effective magnetic flux, then effective magnetic flux is improved, but magnetic dead zone increases due to reduced route to stator
Solution Approach 1:
The permanent magnet is designed with non-uniform thickness, being thicker at the rotation center side and thinner at the outer circumference side. This local variation ensures adequate magnetic flux generation at the center while preventing magnetic dead zones at the outer circumference where excessive thickness would block the magnetic path to the stator.
Solution Approach 2:
The invention introduces dimensional variation in the permanent magnet thickness, making it thicker at the rotation center side and thinner at the outer circumference side. This dimensional change optimizes the balance between effective magnetic flux and magnetic path length, reducing magnetic dead zones while maintaining flux levels.
4Quantity of substance
If the overall thickness of permanent magnets is increased to increase effective magnetic flux, then effective magnetic flux is improved, but cogging torque increases
Solution Approach 1:
The permanent magnet thickness is varied locally, being thicker at the rotation center side and thinner at the outer circumference side. This local optimization increases effective magnetic flux for torque production while reducing the outer circumference thickness to minimize cogging torque, which is generated at the magnet-stator interface.
5Quantity of substance
If the overall thickness of permanent magnets is increased to increase effective magnetic flux, then effective magnetic flux is improved, but total harmonic distortion of counter electromotive force increases
Solution Approach 1:
The permanent magnet is designed with non-uniform thickness, being thicker at the rotation center side and thinner at the outer circumference side. This local variation optimizes the magnetic flux distribution, increasing effective flux for back-EMF generation while reducing outer circumference thickness to minimize harmonic distortions in the counter electromotive force.
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 efficiency and operation performance by minimizing core loss, reducing magnetic dead zones and cogging torque, and improving THD of counter electromotive force, while maintaining effective magnetic flux.
Implementation Method 1
Permanent magnets having poles different from each other are alternatively buried at given intervals in a circumferential direction within the cylindrical rotor
Implementation Method 2
the rotor generates a rotating magnetic field on the teeth of the stator formed between stator slots as the polarity of the coils changes sequentially
Implementation Method 3
If the plurality of coils wound on the plurality of teeth of the stator is successively applied with current, the rotor generates a rotating magnetic field on the teeth of the stator formed between stator slots as the polarity of the coils changes sequentially
Data Source
AI summary
A BLDC motor server includes a stator configured in a hollow cylindrical shape and comprising a plurality of teeth around which a plurality of coils is wound to form an electromagnetic field, respectively; and a rotor configured in a cylindrical shape rotatable within the stator and comprising a plurality of permanent magnets, each having an arched section in which an outer circumference side is extended in both directions from a rotation center side, wherein the plurality of permanent magnets is disposed, so that facing outer surface portions of two permanent magnets neighboring each other are adjacent to each other, and wherein a width Wo of the outer circumference side of each permanent magnet is configured to be smaller than a width Wc of the rotation center side thereof. The BLDC motor may reduce a noise and a vibration as well as increasing an efficiency of the motor.