NTC Inrush Current Limiter With Expansion-Matched Contacts
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Solution Overview
Problem
Existing electronic components for limiting inrush current in start-stop systems of vehicles face challenges due to significant thermal expansion mismatches between NTC elements and conductive materials, leading to mechanical stress and potential component destruction, while also causing voltage drops that can affect safety-critical systems.
Innovation Solution
The design incorporates NTC elements with metallization and flat, thermally and electrically conductive contact elements made from materials like copper, Invar, and Kovar, with a layer structure and sintered silver connections, ensuring thermal expansion matching and stable, durable connections to manage high currents and temperature fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper contact elements are used for high electrical conductivity, then electrical conductivity is improved, but thermal expansion mismatch with NTC ceramic causes mechanical stress and component destruction
Solution Approach 1:
The contact element is constructed as a composite material consisting of a copper base material providing high electrical conductivity and an Invar or Kovar coating layer providing thermal expansion matching with the NTC ceramic. This composite structure simultaneously achieves both high electrical conductivity and compatible thermal expansion characteristics, resolving the contradiction between electrical performance and thermal mechanical stability.
2Volume of moving object
If the NTC element dimensions are reduced to fit compact designs, then device compactness is improved, but electrical resistance increases and current limiting effectiveness decreases
Solution Approach 1:
The patent optimizes the NTC element dimensions and resistance value parameters to achieve the desired current limiting effect in compact form. By carefully selecting the resistance range (0.01-10 ohms at 25°C) and dimensional parameters, the design achieves effective inrush current limitation while maintaining compact size suitable for modern vehicle applications.
3Reliability
If thick copper contact elements are used to reduce electrical resistance, then electrical conductivity is improved, but thermal expansion difference with NTC ceramic increases mechanical stress
Solution Approach 1:
The contact element uses a composite structure with a copper base providing low electrical resistance and a thin Invar or Kovar coating layer providing thermal expansion compatibility. This allows the contact element to maintain low electrical resistance while the coating layer prevents excessive thermal mechanical stress during temperature cycles, resolving the contradiction between electrical conductivity and stress resistance.
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 configuration provides a stable, durable, and efficient inrush current limiter that reduces voltage drops during engine startups, ensuring reliable power supply to critical systems by minimizing thermal stresses and maintaining high conductivity.
Implementation Method 1
An NTC (Negative Temperature Coefficient) component, for example, can be used to reduce the voltage drop
Implementation Method 2
The connecting material creates a stable, highly electrically conductive, and mechanically durable connection between the NTC element and the contact elements
Implementation Method 3
The NTC element is also thermally connected to the respective contact element via the connecting material
Data Source
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AI summary
The invention relates to an electronic component (1) for limiting the inrush current, comprising at least one NTC element (2) and at least two electrically conducting contact elements (3), to each of which the NTC element (2) is connected in an electrically conducting manner via a connection material (7), the thermal expansion coefficient of the contact elements (3) being adapted to the thermal expansion coefficient of the NTC element (2). The invention further relates to the use of an electronic component (1).