PTC Heating Cell with Diagonal Metallization to Reduce NTC Effects
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional PTC heating cells with metallization on opposite main side surfaces face issues with increased ohmic resistance and NTC behavior at low temperatures, particularly at higher voltages, leading to impaired performance and thermal stress.
Innovation Solution
A cuboid-shaped PTC element with diagonally opposed metallizations as strips on its surface, forming a longer current path through the PTC element, reducing thickness to 0.9 mm for high-voltage applications, and incorporating contact rails and insulating layers for secure electrical connections and heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If metallization is located on oppositely disposed main side surfaces with current path in thickness direction, then the structure is simple and manufacturing is easy, but the ohmic resistance increases at higher voltages and NTC behavior is pronounced at low temperatures
Solution Approach 1:
The current path is changed from the thickness direction to a diagonal path through the PTC element. By placing metallizations on diagonally oppositely disposed surface sections, the current flows through a longer path that utilizes both width and thickness dimensions, increasing the number of grain boundaries traversed and improving heating performance at low temperatures.
2Volume of moving object
If the PTC element thickness is reduced to 0.9 mm for compact design, then the device becomes more compact and fits better in vehicle applications, but thermal stress fracture risk increases
Solution Approach 1:
The thickness parameter is optimized to 0.9 mm, which is sufficiently thin for compact vehicle installations but thick enough to avoid thermal stress fracture. This parameter change balances the conflicting requirements of compactness and mechanical strength.
3Quantity of substance
If metallizations are made as thin strips to reduce material usage, then the structure is more compact and material consumption is reduced, but the current path length increases which improves heating efficiency
Solution Approach 1:
Thin strip metallizations are placed on diagonally oppositely disposed surfaces, transforming the current path from a short thickness-direction path to a long diagonal path. This increases the number of grain boundaries the current must traverse, enhancing the PTC effect and heating efficiency while using minimal metallization material.
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 enables compact, high-voltage PTC heating cells with improved thermal performance and reduced NTC effect, suitable for electric vehicles, allowing direct use of on-board voltages up to 1,000 VDC and efficient heat dissipation.
Implementation Method 1
If a voltage is applied to a PTC element, then it heats up
Implementation Method 2
the ohmic resistance of the latter must be increased as the voltage increases
Data Source
AI summary
A PTC heating cell has a cuboid-shaped PTC element and two metallizations electrically separated from each other and provided on the surface of the PTC element for the introduction of current to the PTC element. The two metallizations are provided as strips formed over an entire longitudinal extension (L) of the PTC element on diagonally oppositely disposed surface sections of the PTC element.