Bimetal Thermal Element with Integrated Heater for Extended Tripping Time
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Solution Overview
Problem
Conventional bimetal thermal elements face challenges in achieving long tripping times while maintaining a small volume, as the thickness of multi-strip heaters exceeds the size limitations of product casings, making it difficult to fit them into smaller applications.
Innovation Solution
A bimetal thermal element design featuring a bimetal strip with a notch and a heater made of a resistant strip with a linear and wound portion, where the current path is configured to avoid flowing through the bimetal strip and its support, allowing deflection solely due to temperature rise from the heater, enabling a longer tripping time and reduced thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a multi-strip heater is used to achieve long tripping time, then the tripping time is extended, but the thickness of the bimetal thermal element increases and exceeds the size limitations of product casings
Solution Approach 1:
The heater is configured with a linear portion extending along the bimetal strip and a wound portion that wraps around the bimetal strip, transforming the heater layout from a multi-layer stacked configuration to a spatial arrangement that utilizes the length and circumference dimensions. This dimensional transformation allows achieving the required heater length for long tripping time without increasing the thickness dimension, enabling the thermal element to fit within product casing size limitations.
2Device complexity
If current flows through both the bimetal strip and support, then the structure is simpler, but the deflection is affected by temperature rise from multiple sources making it hard to realize long tripping time
Solution Approach 1:
The current path is specifically designed to extract the heating function from the bimetal strip and support structure, concentrating the heat generation solely in the heater component. The linear portion of the heater extends along the bimetal strip while the wound portion wraps around it, ensuring current flows only through the heater resistance. This separation allows the bimetal strip to deflect based exclusively on heater-induced temperature rise, enabling precise control of tripping time without interference from electromagnetic heating of the support structure.
3Ease of manufacture
If a conventional wound heater is used, then the manufacturing is simpler, but the heater length is insufficient to provide adequate heating for long tripping time applications
Solution Approach 1:
The heater design merges two functional configurations into a single integrated component: a linear portion that extends along the bimetal strip to provide distributed heating, and a wound portion that wraps around the bimetal strip to increase heating length and thermal intimacy. This combination allows the heater to achieve the equivalent length of multi-strip heaters while maintaining the manufacturing simplicity of a single continuous resistant strip, thereby enabling long tripping time applications without complex multi-layer assembly.
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 allows for a longer tripping time by ensuring the bimetal strip warms up solely due to the heater's temperature rise, enabling a two-layer bimetal strip construction, which is thinner and less expensive, with simpler assembly and improved deflection performance.
Implementation Method 1
the deflection of bimetal strip 14 is generated by the temperature-rise coming from the heater 15
Implementation Method 2
detecting the overload currents through the deflection of one or more bimetal strips due to the temperature rise
Data Source
AI summary
A bimetal thermal element adapted to assembling into a support. The bimetal thermal element includes: a bimetal strip having a first end and a second end opposite to the first end, and a notch formed at the first end; a heater made of a resistant strip including a linear portion and a wound portion, wherein the linear portion is straight and extending from a first position near the second end of the bimetal strip in a direction parallel to the bimetal strip and the wound portion is wound around the bimetal strip and the linear portion; and an insulating device to insulate the bimetal strip from the heater. With this design, there is also no current within the bimetal strip and its support, so the deflection of the bimetal strip is generated only by the temperature-rise coming from the resistant strip, therefore, it can realize a long tripping time.