R-T-B Permanent Magnet Composition for Variable Flux Control
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Solution Overview
Problem
Variable magnetic flux motors face efficiency deterioration due to the difficulty in controlling magnetic flux and achieving high residual magnetic flux density in variable magnets, particularly when using R-T-B based magnets, which have low coercivity and sharp magnetic field changes, making it hard to maintain efficiency across wide rotational speed regions.
Innovation Solution
The R-T-B based permanent magnet is formulated with a demagnetization curve slope ΔJ/Δ(H/HcJ) of less than 400 kG, using a composition of (R1(1-x)R2x) with R1 being rare earth elements like Pr, Nd, Sm, and R2 being Y, Ce, or La, and T including Fe or Co, to achieve high residual magnetic flux density and low coercivity, allowing for controlled magnetization by a small external magnetic field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If R-T-B based permanent magnet with conventional composition is used as variable magnet, then coercivity is reduced, but residual magnetic flux density decreases and magnetic field changes sharply making control difficult
Solution Approach 1:
The patent changes the chemical composition parameters of the R-T-B magnet by incorporating specific rare earth elements (Pr, Nd, Sm in R1 and Y, Ce, La in R2) with controlled ratios (0.2≤x≤0.7), which modifies the magnetic properties to achieve both low coercivity and high residual magnetic flux density, enabling smooth controllable magnetic field changes
Solution Approach 2:
The patent creates a composite rare earth structure (R1(1-x)R2x) where different rare earth elements are combined in specific proportions, resulting in a material that exhibits optimized magnetic properties including low coercivity, high residual magnetic flux density, and controlled demagnetization characteristics
2Ease of operation
If variable magnet with low coercivity is used, then magnetic flux controllability improves, but residual magnetic flux density decreases leading to lower motor output and efficiency
Solution Approach 1:
The patent optimizes the composition parameters by selecting specific rare earth elements and their ratios (0.2≤x≤0.7) to simultaneously achieve high residual magnetic flux density (≥12.5 kG) and low coercivity, ensuring both high motor power and ease of magnetic flux control
3Speed
If field weakening control is applied in intermediate/high speed region, then induced voltage is suppressed below supply voltage, but motor efficiency deteriorates
Solution Approach 1:
The patent enables dynamic control of magnetic flux by using a variable magnet with specifically optimized magnetic properties (low coercivity, high residual magnetic flux density), allowing the motor to adapt magnetic flux to operating conditions and maintain high efficiency across a wide speed range through reduced reliance on field weakening control
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 formulation enables a variable magnet with high residual magnetic flux density and low coercivity, improving the efficiency and controllability of the magnetic flux, suitable for use in variable magnetic flux motors across a wide rotational speed range.
Implementation Method 1
The R-T-B based permanent magnet (R represents a rare earth element, T represents Fe or Fe with part of it replaced with Co, and B represents boron) having the tetragonal compound R2T14B as the main phase is known to have excellent magnetic properties
Implementation Method 2
a magnet in which the magnetic force changes reversibly via an external magnetic field (a variable magnetic force magnet)
Data Source
AI summary
The present invention provides a R-T-B based permanent magnet, comprising a demagnetization curve having a slope ΔJ/Δ(H/HcJ) of less than 400 kG at a region where the value of magnetic field is Hk or less, wherein it is preferable that R in the composition of R-T-B is represented by (R11-xR2x), and T represents one or more transition metal elements containing Fe or a combination of Fe and Co as necessary, where: R1 represents the rare earth element(s) composed of one or more elements selected from the group consisting of Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and R2 contains at least one element selected from the group consisting of Y, Ce and La, and 0.2≤x≤0.7.