Mapping Open to Closed Circuit Demagnetisation Curves
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Solution Overview
Problem
Existing methods for measuring demagnetisation curves in magnetic materials, particularly rare-earth materials, face inaccuracies when transitioning from open to closed magnetic circuits due to self-demagnetisation field effects and eddy currents, leading to protocol and geometry-dependent results.
Innovation Solution
A multi-stage method involving pulsed field magnetometry to measure open circuit demagnetisation curves, correcting for linear and non-linear eddy current effects, sample geometry, and adding idealised steel core effects to accurately map these curves to closed circuit demagnetisation curves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If closed magnetic circuit permeameter measurements are used, then measurement precision and reliability are improved, but device complexity and cost increase
Solution Approach 1:
The patent introduces a steel core as an intermediary element in the permeameter system. This steel core acts as a magnetic flux conduit that guides and concentrates the magnetic flux through the sample, enabling accurate closed-circuit measurements without requiring complex external magnetic field generation systems. The steel core with its high permeability creates a well-defined magnetic circuit path, simplifying the overall measurement system while maintaining high precision.
2Productivity
If open magnetic circuit PFM measurements are used, then measurement speed and cost are improved, but measurement precision deteriorates due to self-demagnetisation field effects
Solution Approach 1:
The steel core serves as a mediator that transforms the open-circuit measurement configuration into an effective closed-circuit configuration. By introducing this high-permeability intermediate element, the system maintains the speed advantages of PFM while achieving the measurement precision traditionally associated only with slow closed-circuit permeameter methods.
Solution Approach 2:
The patent changes the magnetic circuit parameter from open to closed configuration by introducing the steel core. This parameter change fundamentally alters the magnetic field distribution and eliminates self-demagnetisation effects, thereby improving measurement precision while maintaining the fast measurement capability of PFM systems.
3Strength
If open magnetic circuit measurements are used for rare-earth materials, then saturation field requirements are reduced, but measurement accuracy deteriorates due to eddy current effects
Solution Approach 1:
The steel core acts as an intermediary that provides a low-reluctance path for magnetic flux, enabling the system to achieve high saturation fields necessary for measuring rare-earth materials without requiring excessively strong external fields. This intermediate magnetic pathway reduces the burden on the external field generation system while maintaining measurement accuracy.
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
Enhances the accuracy of demagnetisation curve mapping to within the precision of permeameter and PFM measurements, improving the reproducibility and reliability of magnetic material characterisation.
Implementation Method 1
Pulsed field measurements use high frequency magnetisation pulses that additionally induce eddy currents in the system
Implementation Method 2
induce eddy currents in the system, introducing a distortion in the measured characteristic
Implementation Method 3
Magnetic materials are characterised and graded by their hysteresis loop
Implementation Method 4
rare-earth materials, such as samarium cobalt and neodymium require large saturation and coercive fields
Data Source
AI summary
A method and apparatus for accurately mapping the closed magnetic circuit demagnetisation curve to and from a open magnetic circuit demagnetisation curve. The method utilises open circuit data from a pulsed field magnetometer (PFM) and computer modelling of both the PFM (open circuit) and permeameter (closed circuit) apparatus. This method is more accurate than previous methods and can calculate the closed circuit curve within the precision of both the PFM and the permeameter apparatus.