Thermal Protector Movable Plate Composite Design
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Solution Overview
Problem
Conventional thermal protectors using copper alloy for movable plates experience excessive deterioration at high temperatures, leading to reduced spring performance and increased internal resistance, which causes the operating temperature to drop significantly when handling large currents.
Innovation Solution
A thermal protector design featuring a movable plate made of precipitation-hardened stainless steel and a bypass member made of high-conductivity aluminum, where the two components are joined and subjected to heat treatment to maintain contact pressure and reduce internal resistance, preventing the operating temperature from dropping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper alloy is used for the movable plate, then low internal resistance is achieved, but spring performance deteriorates excessively at high temperatures
Solution Approach 1:
The movable plate is constructed as a composite structure combining stainless steel (for spring performance at high temperatures) and copper alloy (for low internal resistance). The copper alloy layer is formed on the stainless steel base through plating or cladding, creating a material composite that simultaneously achieves both required properties.
Solution Approach 2:
Different regions of the movable plate have different material compositions optimized for their specific functions. The base portion requires high temperature resistance and spring performance (stainless steel), while the contact portions require low resistance (copper alloy). This local differentiation of material properties resolves the contradiction.
2Temperature
If stainless steel is used for the movable plate, then spring performance is maintained at high temperatures, but internal resistance increases causing operating temperature to drop
Solution Approach 1:
The movable plate combines stainless steel and copper alloy in a composite structure where each material contributes its advantageous property. The stainless steel provides high temperature stability and spring performance, while the copper alloy coating reduces internal resistance to acceptable levels.
Solution Approach 2:
The material composition parameters of the movable plate are optimized by controlling the thickness and distribution of the copper alloy layer on the stainless steel base. This parameter optimization achieves the balance between maintaining spring performance at high temperatures and keeping internal resistance low.
3Reliability
If copper alloy is used for the movable plate, then low internal resistance is achieved, but contact pressure is lost at high temperatures
Solution Approach 1:
The composite structure of stainless steel base with copper alloy coating ensures that the stainless steel maintains spring performance and contact pressure at high temperatures, while the copper alloy maintains low contact resistance at the contact surfaces.
Solution Approach 2:
The movable plate has differentiated material properties: the stainless steel base provides mechanical properties (spring performance and contact pressure) throughout the structure, while the copper alloy surface layer provides electrical properties (low resistance) at the contact points.
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 solution effectively maintains spring performance and contact pressure at high temperatures while reducing internal resistance, allowing the thermal protector to handle larger currents efficiently without significant temperature drops.
Implementation Method 1
the movable plate and the bypass member are joined together and are subjected to heat treatment so that the first metal material of the bypass member is softened while the second metal material of the movable plate is precipitation-hardened
Implementation Method 2
the movable plate and the bypass member are joined together and are subjected to heat treatment so that the first metal material of the bypass member is softened while the second metal material of the movable plate is precipitation-hardened
Implementation Method 3
a thermal responsive element for moving the movable contact point of the movable plate by a snap action thereof to open and close the electric circuit
Implementation Method 4
the bypass member is formed of a first metal material having a higher conductivity than a second metal material of which the movable plate is formed
Implementation Method 5
maintaining a contact pressure at a contact point even under high temperatures
Data Source
AI summary
A thermal protector for opening and closing an electric circuit, includes: a movable plate having a movable contact point mounted on a one end portion thereof and having a terminal mounted on an opposite end portion thereof; a bypass member joined to the movable plate at the end portions of the movable plate on which the movable contact point and the terminal are mounted; and a thermal responsive element for moving the movable contact point of the movable plate by a snap action thereof to open and close the electric circuit, wherein the bypass member is formed of a first metal material having a higher conductivity than a second metal material of which the movable plate is formed, and the movable plate and the bypass member are joined together and are subjected to heat treatment so that the first metal material of the bypass member is softened while the second metal material of the movable plate is precipitation-hardened.