PTC Thermistor Voltage Drop Limits for Harmonic Reduction
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Solution Overview
Problem
PTC thermistors used with alternating current produce undesirable current distortions in the form of harmonics, which are particularly problematic in mobile applications like aviation where high-quality on-board voltage is crucial.
Innovation Solution
Limiting the voltage drop across the PTC thermistor to 40 V/mm or less by dimensioning it appropriately, using multiple elements connected in series or parallel, or a combination of both, to reduce harmonic oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a PTC thermistor is operated with alternating current, then heating function is achieved, but current distortion and harmonic oscillations are produced
Solution Approach 1:
The patent applies parameter changes by limiting the voltage drop across the PTC thermistor to a specific range (10-40 V/mm) to reduce current distortion while maintaining heating functionality. This involves adjusting electrical parameters (voltage drop per unit length) to optimize the balance between heating effect and harmonic generation.
2Power
If the voltage drop across the PTC thermistor is increased, then heating efficiency is improved, but current distortion and harmonic oscillations increase
Solution Approach 1:
The patent establishes an optimal parameter range for voltage drop (10-40 V/mm) that balances heating efficiency with harmonic reduction. By constraining the voltage drop within this range, the system achieves effective heating while limiting current distortion to acceptable levels.
3Device complexity
If a thick PTC thermistor is used, then device complexity is reduced, but voltage drop per unit length increases causing more harmonics
Solution Approach 1:
The patent transforms the geometric parameter (thickness) into a controlled voltage drop parameter (V/mm). Instead of simply using thicker or thinner thermistors, the invention focuses on the voltage drop per unit length, allowing flexible design choices that meet the harmonic limitation requirement while achieving the desired heating performance.
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
Significantly reduces current distortion, particularly the 3rd harmonic, resulting in a largely undisturbed current or voltage curve, effectively addressing the issue in mobile applications such as aviation.
Implementation Method 1
A PTC thermistor is understood to mean a current-conducting material or a component having such material, the material being designed in such a way that its electrical resistance increases as the temperature rises. Such materials therefore have a positive temperature coefficient.
Implementation Method 2
the PTC thermistor is designed in such a way that its electrical resistance increases as the temperature rises
Data Source
Figure 1~2
Figure 3
AI summary
The present invention relates to a device with at least one PTC thermistor and at least one AC voltage source connected to the PTC thermistor, the PTC thermistor being dimensioned such that the voltage drop across the PTC thermistor does not exceed the value of 40 V/mm.