Nd-Fe-B Variable Flux Magnet Composition
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The Sm—Co based permanent magnet used in variable magnetic flux motors has a lower residual magnetic flux density compared to conventional Nd—Fe—B based magnets, leading to decreased motor output and efficiency.
Innovation Solution
A permanent magnet composed of at least 75% Nd and up to 25% of rare earth elements like Y, Ce, La, or other elements, with a crystal structure of R2Fe14B, and a specific composition ratio to achieve high residual magnetic flux density and low coercivity, allowing for reversible magnetic field control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If Sm—Co based permanent magnet is used as variable flux magnet, then coercivity is improved, but residual magnetic flux density deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition ratio of rare earth elements (R) to be 11.8-12.2 at%, and the cross-sectional area ratio of R-rich phase (Are) to be 0-20%. This specific parameter range optimizes the balance between coercivity and residual magnetic flux density, resolving the contradiction between these two magnetic properties.
Solution Approach 2:
The patent uses composite material structure consisting of main phase (R2Fe14B) and R-rich phase subphase. This composite structure allows the material to exhibit both high coercivity (from the main phase) and high residual magnetic flux density (from the optimized R-rich phase distribution), thereby resolving the contradiction between these two properties.
2Quantity of substance
If Nd—Fe—B based permanent magnet is used as fixed flux magnet, then residual magnetic flux density is improved, but adaptability to variable flux control deteriorates
Solution Approach 1:
The patent changes the magnetic property parameters by controlling the R content at 11.8-12.2 at% and Are at 0-20%, which creates a magnet with both high residual flux density and low enough coercivity for variable flux control, thus resolving the contradiction between maintaining high flux density and enabling variable flux adaptability.
Solution Approach 2:
The patent creates a dynamic magnetization state by optimizing the R-rich phase distribution, allowing the magnet to be easily demagnetized and remagnetized by external magnetic fields while maintaining high residual flux density, thereby achieving both high flux density and variable flux control capability.
3Power
If variable flux magnet with high residual magnetic flux density is designed, then motor output is improved, but magnetization control difficulty increases
Solution Approach 1:
The patent optimizes the composition parameters (R: 11.8-12.2 at%, Are: 0-20%) to achieve the optimal balance point where the magnet has sufficiently high residual magnetic flux density for high motor output while maintaining sufficiently low coercivity for easy magnetization control with small external magnetic fields.
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 magnet provides high output and efficiency for variable magnetic flux motors with a variable flux magnet having low coercivity and high residual magnetic flux density, matching the performance of fixed flux magnets while allowing for efficient magnetization control with a small external magnetic field.
Implementation Method 1
a permanent magnet composed of at least 75% Nd and up to 25% of rare earth elements like Y, Ce, La, or other elements, with a crystal structure of R2Fe14B, and a specific composition ratio to achieve high residual magnetic flux density and low coercivity, allowing for reversible magnetic field control
Implementation Method 2
the variable magnetic flux motor is demagnetized through a current magnetic field in order to inhibit the increase of back electromotive force that will prevent roll controlling during revolution at a high speed, and the motor is remagnetized through the current magnetic field when the torque is needed during the operation
Data Source
AI summary
The present invention provides a permanent magnet suitable as a variable flux magnet for a variable magnetic flux motor. A permanent magnet comprising R (R is composed of 75 at % or more of Nd and 25 at % or less of at least one element selected from the group consisting of Y, Ce, La, Pr, Sm, Eu, Gd, Er, Tm, Yb and Lu), Fe and B as the main component, wherein, said permanent magnet is composed of a main phase of a crystal structure represented by R2Fe14B, a ratio of the element R to all constituent element satisfies 11.8 at %≦R≦12.2 at %, a cross-sectional area ratio Are of the sub-phase with a higher concentration of R than that of the main phase to the whole magnet structure satisfies 0%<Are≦1.3%, and a cross-sectional area ratio Ama of the main phase to the whole magnet structure is 97%≦Ama.