Overload Release Metal Strip Segmentation for Circuit Breakers
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Solution Overview
Problem
The use of copper-plated steel materials in electromechanical protection devices, such as circuit breakers, poses economic and technical challenges due to high material costs and reduced rigidity, leading to difficulties in connecting metal parts and bimetallic strips, especially at high current ranges.
Innovation Solution
The mechanical and electrical connections of the metal strip are completely or partially separated, allowing for optimized connections without current flow through the mechanical connection, enabling the use of inexpensive steel for mechanical fixing and direct copper connection for electrical conduction, reducing material waste and manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If copper-plated steel materials are used for the metal part, then the material provides required rigidity and can be welded to the bimetallic strip, but the material cost is approximately twice as high as pure copper bands and heating of the metal part during operation increases
Solution Approach 1:
The invention divides the metal part into two functionally distinct sections: a steel core component providing mechanical strength and rigidity, and a copper coating layer providing electrical conductivity and thermal conductivity. This segmentation allows each material to perform its optimal function while reducing overall material cost compared to using copper-plated steel throughout.
Solution Approach 2:
The metal part is designed with non-uniform copper plating thickness distribution, where thicker copper coating is applied in regions requiring high electrical and thermal conductivity (such as areas in contact with heating conductors), while thinner or no copper plating is used in regions where only mechanical strength is required. This local quality optimization reduces material cost while maintaining functional performance.
2Loss of energy
If the thickness of copper plating is increased to reduce resistance and heating, then the material cost increases and the steel content is reduced, but the metal part loses rigidity and welding connection problems occur
Solution Approach 1:
The copper plating thickness is optimized locally rather than uniformly throughout the metal part. Thicker copper layers are applied specifically in high-current density regions and areas with heating conductors where thermal and electrical conductivity are critical, while thinner plating or exposed steel is used in structural regions where rigidity is paramount. This resolves the contradiction by matching material properties to functional requirements.
Solution Approach 2:
The metal part utilizes a composite structure combining steel substrate with copper coating layers of varying thicknesses. This composite material approach allows the steel to provide mechanical rigidity and structural integrity, while the copper layers provide electrical and thermal conductivity where needed, optimizing both rigidity and energy loss characteristics simultaneously.
3Ease of manufacture
If copper-plated steel material is used, then welding to bimetallic strip is easy under certain conditions, but the waste material from stamping as mixed metal scrap brings in small income and manufacturing costs increase
Solution Approach 1:
The invention changes the material composition parameters by using a steel-based substrate rather than copper-plated steel, fundamentally altering the material properties. This parameter change enables the use of pure steel stamping processes that produce homogeneous steel scrap with higher recycling value, while welding connectivity is maintained through the steel-to-bimetallic-strip interface.
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 solution achieves thermal economy and improved mechanical and electrical performance by minimizing the use of expensive copper-plated materials, enhancing rigidity and safety during high current operations while maintaining efficient heating management.
Implementation Method 1
If current is flowing through the bimetallic strips, i.e. the bimetallic strips are heated directly
Implementation Method 2
bimetallic or trimetallic strips are used as overload releases
Data Source
AI summary
An overload release is disclosed, in particular for a circuit breaker, including a metal strip which is made of at least two different types of metal and around which a heat conductor is wound. In an embodiment, the mechanical and electrical connection of the metal strip can be completely or partly disconnected, such that no current flows over the mechanical connection of the metal strip in the completely disconnected case and a portion of the current flows over the mechanical connection in the partly disconnected case.