Magnetic Core Assembly Using Temporary Ferrite Magnet
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Solution Overview
Problem
The assembly of laminated magnetic cores for transformers is laborious and time-consuming due to the need to avoid air gaps, which reduces transformer efficiency, and existing methods do not effectively compensate for manufacturing tolerances without increasing the number of core segments.
Innovation Solution
The use of a permanent magnet to hold sheet metal stacks together during assembly by magnetizing them, allowing for simplified assembly of the magnetic core by magnetic force, with low-cost ferrite magnets being used that lose magnetic force at operating temperatures, thus avoiding air gaps in the magnetic circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the number of core segments is reduced to simplify assembly, then assembly effort is reduced, but air gaps due to manufacturing tolerances cannot be avoided
Solution Approach 1:
A temporary magnet is introduced as an intermediary tool during the assembly process. This magnet temporarily holds the core segments together through magnetic attraction, compensating for manufacturing tolerances and preventing air gaps. After assembly is complete, the temporary magnet is removed, and the core segments remain securely assembled without air gaps despite the reduced number of segments.
2Reliability
If conventional permanent magnets with high magnetization are used, then magnetic core efficiency is improved, but cost increases due to rare earth materials
Solution Approach 1:
The patent employs inexpensive ferrite permanent magnets instead of expensive rare earth magnets. These ferrite magnets have lower magnetization and lower Curie temperature, making them suitable only for the assembly process rather than for improving transformer efficiency during operation. After assembly, they are removed, serving as disposable assembly aids that reduce cost without compromising the final product's performance.
Solution Approach 2:
The magnetic function is extracted from the permanent magnets used during assembly. The magnets serve solely for assembly purposes and are removed after assembly is complete. This separation allows the use of cheap ferrite magnets for assembly without requiring the expensive high-performance magnets that would be needed if the magnets remained in the final product to improve efficiency.
3Ease of manufacture
If ferrite magnets with low Curie temperature are used to reduce cost, then production cost decreases, but magnetic force is lost at operating temperatures
Solution Approach 1:
Ferrite magnets with low Curie temperature are used specifically for the assembly process where cost reduction is prioritized. Since these magnets are removed after assembly, their inability to maintain magnetic force at high operating temperatures does not affect the transformer's performance. The temporary nature of their use allows exploitation of their cost advantage without suffering from their thermal limitations.
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 method simplifies the assembly of laminated magnetic cores and reduces the effort required to create air-gap-free magnetic circuits, making it suitable for transformers like ignition coils that face thermal loads, while using cost-effective ferrite magnets that do not compromise efficiency due to their inferior properties.
Implementation Method 1
By placing the permanent magnet against a first sheet metal stack forming a core segment, this sheet metal stack is magnetized and from then on is held together by magnetic force
Implementation Method 2
A further sheet metal stack, which forms a further core segment, is then placed at the permanent magnet, or the already magnetized sheet metal stack. By this means the further sheet metal stack is also magnetized and from then on is held together by magnetic force
Data Source
AI summary
A method is described for the assembly of a magnetic core for a transformer, with the following steps: Cutting sheet metal blanks from transformer sheet, stacking the sheet metal blanks to form magnetic core segments, placing a permanent magnet at one of the magnetic core segments so that the latter is magnetized by the permanent magnet, formation of the magnetic core by placing the remaining magnetic core segments against the permanent magnet, or against a magnetic core segment already magnetized by the permanent magnet. A magnetic core is also disclosed.