Permanent-Magnet Inductive Core for Low High-Frequency Losses
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Inductors used in high-frequency power converters experience significant magnetic losses and heat dissipation due to high magnetic induction, especially when operating at frequencies above 1 MHz, which are not effectively mitigated by existing magnetic polarization methods, leading to inefficiencies and increased component size and cost.
Innovation Solution
An inductance core design that incorporates permanent magnets arranged to generate magnetic flux lines in opposite directions within a ferromagnetic material, canceling the continuous component of magnetic induction and reducing peak induction values, thereby minimizing magnetic and thermal losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ferrite-type oxide materials are used as inductance cores for high-frequency operation, then stable permeability and high electrical resistivity are achieved, but magnetic losses increase with frequency and induction peak value
Solution Approach 1:
The patent applies preliminary anti-action by introducing a direct current through a polarization winding that generates a magnetic field opposing the alternating magnetic field. This preliminary opposing action reduces the peak induction value in the core, thereby decreasing magnetic losses before the main operating cycle begins. The DC polarization current is specifically calibrated to counterbalance the harmful effects of high-frequency alternating fields.
Solution Approach 2:
The patent changes the magnetic parameter of the core by superimposing a DC magnetic field from the polarization winding onto the AC magnetic field from the inductor winding. This parameter change modifies the operating point on the B-H curve, reducing the peak induction value and moving the operation to a region with lower hysteresis and eddy current losses, thus reducing overall magnetic losses while maintaining stable permeability.
2Loss of energy
If a direct current is circulated around the core to generate magnetic polarization, then magnetic losses are reduced, but device bulk and additional cost increase
Solution Approach 1:
The patent merges the polarization function with the core structure itself by integrating the polarization winding directly into the core assembly. The winding is positioned to closely couple with the core, combining the magnetic polarization function with the inductance function in a unified structure. This integration reduces the number of separate components and reduces overall device bulk compared to external polarization systems.
Solution Approach 2:
The polarization winding serves multiple functions: it generates the DC magnetic field for reducing peak induction, and its placement within the core structure also provides structural support and magnetic coupling. This multi-functionality reduces the need for additional dedicated components, thereby reducing device complexity and bulk while maintaining the energy loss reduction benefit.
3Loss of energy
If magnets are inserted into the core to generate magnetic polarization, then magnetic flux circulation is improved, but magnetic leakage increases for low permeability materials
Solution Approach 1:
The patent uses the ferromagnetic core material as an intermediary between the magnet's magnetic flux and the inductor winding. The core provides a low-reluctance path that guides and confines the magnetic flux, preventing direct leakage into the surrounding environment. This intermediary role of the core effectively couples the magnet's polarization field to the winding while minimizing harmful magnetic radiation.
Solution Approach 2:
The patent applies local quality by positioning the magnets specifically within cavities in the core structure where they can generate localized magnetic polarization exactly where needed. This localized approach ensures that the magnetic flux is concentrated in the core material rather than leaking outward, and the high-permeability core material locally channels the flux along desired paths, reducing overall magnetic leakage while maintaining effective polarization.
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 core design significantly reduces magnetic losses and heat dissipation, allowing for efficient operation at high frequencies with reduced component size and cost, particularly suitable for inductors with low magnetic permeability materials.
Implementation Method 1
The magnets are arranged relative to each other and to the ferromagnetic material so as to generate magnetic flux lines (Fm) circulating in opposite directions to those produced by the winding (Fw)
Implementation Method 2
A first solution consists of generating a magnetic polarization by circulating a direct current around the core... A second solution is to generate magnetic polarization by means of magnets inserted into an area of the core
Implementation Method 3
The core comprises a body (2) formed of a ferromagnetic material (4)... The ferromagnetic material is placed as close as possible to the magnet between its poles on the natural path of the magnetic flux lines produced by the magnet
Implementation Method 4
magnetic losses increase with frequency and with the peak value of magnetic induction... The peak value of the variable induction can be written: Bpeak = BDC + ΔB/2... magnetic losses are reduced as well as thermal losses
Data Source
Figure 1A~2A
Figure 2B~3
Figure 4A~4B
AI summary
Inductive core (N1) including a body (2) comprising a ferromagnetic material (4) and a magnet (6), the magnet (6) forming a first path for circulating of magnetic flux lines produced by the magnet (6), and the ferromagnetic material (4) at least partially forming a second path for circulating said magnetic flux lines, wherein the ferromagnetic material (4) extends continuously between the poles of the magnet (6) along the latter (6) and makes contact with at least some of an exterior lateral wall of the magnet (6) extending between its poles.