PTC Resistor Voltage Gradient Limit for Low-Harmonic AC Heating
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Solution Overview
Problem
PTC resistors used in AC applications can cause current distortions due to harmonic vibrations, which are undesirable in high-quality on-board voltage systems, particularly in mobile applications like aeronautics.
Innovation Solution
Limiting the voltage drop across PTC resistors to 40 V/mm or less by adjusting their dimensions or connecting multiple resistors in series/parallel to reduce harmonic distortions, specifically targeting the 3rd harmonic in the fundamental oscillation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If PTC resistors are operated with AC current, then heating function is achieved, but current distortion occurs due to harmonic vibrations
Solution Approach 1:
The patent applies parameter changes by controlling the voltage drop across the PTC resistor to remain below a specific threshold (40 V/mm). This parameter control modifies the operating conditions of the PTC resistor to reduce harmonic generation while preserving the heating function. By adjusting the voltage gradient parameter, the invention eliminates current distortion without sacrificing the beneficial heating effect.
2Power
If voltage drop across PTC resistor is increased, then heating efficiency improves, but harmonic distortion increases
Solution Approach 1:
The patent resolves this contradiction by establishing an optimal parameter range for the voltage drop (below 40 V/mm). This parameter optimization allows the system to achieve sufficient heating efficiency while maintaining acceptable current quality. The specific voltage threshold represents the boundary where heating performance is maintained but harmonic distortion is suppressed.
3Volume of moving object
If PTC resistor dimensions are reduced, then device size decreases, but voltage drop per unit length increases causing more distortion
Solution Approach 1:
The patent addresses this contradiction by focusing on the voltage gradient dimension (V/mm) rather than simply scaling the resistor size. By controlling the voltage drop per unit length, the invention allows for compact designs while preventing excessive harmonic distortion. This dimensional approach to parameter control enables miniaturization without sacrificing current quality.
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
Substantially reduces current and voltage distortions, ensuring a largely non-distorted current evolution and voltage evolution, particularly in aircraft applications, while maintaining the temperature-dependent resistance advantage of PTC resistors.
Implementation Method 1
A PTC resistor is understood as a current conductive material or a component having such a material, with the material being made such that its electrical resistance increases as the temperature rises. Such materials thus have a positive temperature coefficient.
Implementation Method 2
The PTC resistor is made as a heating element or as a component of a heating device
Data Source
AI summary
The present invention relates to a device having at least one PCT resistor and having at least one AC voltage source connected to the PTC resistor, with the PTC resistor being dimensioned such that the voltage drop over the PTC resistor does not exceed the value of 40 V/mm.