R-T-B Permanent Magnet Composition for Variable Flux Motors
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Solution Overview
Problem
Variable magnetic flux motors face efficiency deterioration due to the limited residual magnetic flux density and coercivity of existing variable magnets, which hinder efficient operation across a wide rotational speed range, especially when the magnetic force needs to be adjusted under varying load conditions.
Innovation Solution
The development of an R-T-B based permanent magnet with a residual magnetic flux density of 1.2 T or more and coercivity of 640 kA/m or less, utilizing a specific composition of (R1−xR2x)2T14B with R1 being rare earth elements like Pr, Nd, Sm, and R2 including Y, La, and Ce, allowing for effective remagnetization with a small external magnetic field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a variable magnet with low coercivity is used to enable magnetic force adjustment with a small external magnetic field, then the ease of operation is improved, but the residual magnetic flux density decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition parameters of the R-T-B based permanent magnet. Specifically, it limits the total content of Y, La, and Ce to 5 atomic % or less, and controls the R2T14B phase content to 90 vol % or more. These parameter adjustments enable the magnet to achieve both low coercivity (≤640 kA/m) for easy magnetic force adjustment and high residual magnetic flux density (≥1.2 T) for strong magnetic output.
2Ease of operation
If the total content of Y, La, and Ce is increased to reduce coercivity, then the ease of operation is improved, but the residual magnetic flux density decreases
Solution Approach 1:
The patent resolves this contradiction through parameter changes by establishing an optimal composition range: the total content of Y, La, and Ce is controlled to 5 atomic % or less. This parameter control prevents excessive reduction in coercivity while avoiding the significant drop in residual magnetic flux density that would occur with higher concentrations of these rare earth elements.
Solution Approach 2:
The patent employs composite materials by creating a multi-phase structure consisting of R2T14B main phase (90 vol % or more), R-rich grain boundary phase, and secondary phases. This composite structure allows the magnet to achieve both low coercivity and high residual magnetic flux density by optimizing the interaction between different phases, where the R2T14B phase provides high magnetic flux density while the grain boundary phase contributes to coercivity control.
3Quantity of substance
If the R2T14B phase content is increased to improve residual magnetic flux density, then the residual magnetic flux density is improved, but the coercivity increases
Solution Approach 1:
The patent resolves this contradiction through parameter changes by controlling the R2T14B phase content to be 90 vol % or more while simultaneously limiting Y+La+Ce to 5 atomic % or less. This dual parameter control achieves the optimal balance: the high R2T14B phase content ensures residual magnetic flux density of 1.2 T or more, while the limited rare earth element content prevents coercivity from exceeding 640 kA/m.
4Ease of operation
If a small external magnetic field is used for remagnetization, then the ease of operation is improved, but the magnetic force adjustment range is limited
Solution Approach 1:
The patent applies parameter changes by optimizing the magnetic properties through composition control. By limiting Y+La+Ce to 5 atomic % or less and ensuring R2T14B phase content is 90 vol % or more, the magnet achieves coercivity ≤640 kA/m, which enables remagnetization with a small external magnetic field. Simultaneously, the high residual magnetic flux density (≥1.2 T) ensures a wide magnetic force adjustment range for versatile operation.
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 magnet maintains high efficiency and enables reversible magnetic force adjustment, suitable for variable magnetic flux motors, by achieving a high residual magnetic flux density and low coercivity, ensuring stable performance across different operational conditions.
Implementation Method 1
R-T-B based permanent magnet with the tetragonal compound R2T14B being its main phase has excellent magnetic properties
Implementation Method 2
The R-T-B based magnet with the rare earth element(s) R composed of Nd, Pr, Dy, Ho and/or Tb has a large magnetic anisotropy field Ha
Data Source
AI summary
An R-T-B based permanent with the residual magnetic flux density Br2 satisfies the relationship of Br2/Br≥0.90, wherein the residual magnetic flux density Br2 is obtained after applying the external magnetic field of Hex and then applying an external magnetic field of 0.95 HcJ. Such a R-T-B based permanent magnet preferably contains main phase grains with a composition of (R11−xR2x)2T14B (R1 is 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, R2 is element(s) containing at least one selected from the group consisting of Y, La and Ce, T is one or more transition metal elements including Fe or a combination of Fe and Co as essential elements, and 0.2≤x≤0.7) and thus can be suitably used as a magnet with a variable magnetic force for a variable magnetic flux motor.