Carbon Composite Heater Prevents Dielectric Breakdown

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Solution Overview

Problem

Conventional carbon heaters using carbon fibers face issues with dielectric breakdown and plasma formation under high voltage, leading to reduced radiation efficiency due to the narrow distance between filaments and the need for a shield member.

Innovation Solution

A carbon composite composition comprising 50-75 wt.% SiC, 24% or less SiO2, 15-30% novolac resin, and 0.1-10% graphite, which prevents dielectric breakdown and plasma formation by eliminating local voltage concentration and allowing for flexible heater design without the need for a shield member.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If carbon fiber is used as heating element, then high thermal conductivity and heat resistance are achieved, but dielectric breakdown and plasma formation occur under high voltage due to narrow filament intervals

Engineering Contradiction:
Improveheat resistanceVSAvoiddielectric breakdown resistance
Core Design Contradiction:
TemperatureVSReliability

Solution Approach 1:

The invention changes the physical parameters of the heating element by transitioning from fibrous carbon structure to platelet carbon structure with interspersed inert particles. This structural parameter change increases the minimum distance between conductive regions, reducing electric field intensity and preventing dielectric breakdown while maintaining high temperature resistance

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The invention creates a composite material system combining platelet carbon particles with inert particles (alumina, silica, or magnesia) dispersed in a carbon matrix. This composite structure prevents direct conductive pathways between opposite sides of the heating element, eliminating plasma formation while preserving thermal conductivity for high-temperature operation

Inventive Principle:
Principle #40Composite materials

2Object-affected harmful factors

If shield member is added to suppress plasma reaction, then plasma-related harmful effects are reduced, but radiation efficiency is greatly lowered due to blocking radiation light

Engineering Contradiction:
Improveplasma suppressionVSAvoidradiation efficiency
Core Design Contradiction:
Object-affected harmful factorsVSLoss of energy

Solution Approach 1:

The invention extracts and eliminates the need for shield members by redesigning the heating element structure itself. By using platelet carbon with inert particle interspersion, the heating element inherently prevents plasma formation and dielectric breakdown, removing the requirement for additional shielding components that would block radiation

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The inert particles (alumina, silica, or magnesia) serve as intermediary elements within the heating element structure, physically separating conductive carbon regions and preventing electron discharge pathways. This internal mediation eliminates plasma formation without requiring external shield members, thus maintaining full radiation efficiency

Inventive Principle:
Principle #24Intermediary (Mediator)

3Strength

If conventional carbon fiber structure is used, then flexibility and high strength are achieved, but local voltage concentration occurs between filaments causing dielectric breakdown

Engineering Contradiction:
Improvemechanical strengthVSAvoidvoltage distribution uniformity
Core Design Contradiction:
StrengthVSReliability

Solution Approach 1:

The invention applies local quality by creating regions of different electrical properties within the heating element. Platelet carbon particles provide conductive heating regions while interspersed inert particles create insulating regions, locally preventing voltage concentration and electron discharge pathways that would occur between parallel filaments

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

Instead of using continuous fibrous structures that create uniform conductive pathways prone to breakdown, the invention inverts the approach by using discrete platelet particles with insulating material between them. This reverses the conductivity distribution pattern, creating inherent electrical isolation that prevents dielectric breakdown while maintaining structural integrity

Inventive Principle:
Principle #13The other way round (Inversion)

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 carbon composite composition prevents dielectric breakdown and plasma formation, enhances radiation efficiency, and allows for the production of heaters with various shapes and sizes, improving electrical design freedom and reducing the need for post-treatment processes like surface coating.

Implementation Method 1

Since the CF is made of a material called 'carbon', it has a microwave absorption property of carbon itself.

Methodology Applied
Scientific EffectMicrowave absorption: Absorption (EM radiation)

Implementation Method 2

a carbon heater, which is generally used as the sheath heater 5 and the heater 6, is a grill heater that heats food inside the cavity 2 using a radiant heating method

Methodology Applied
Scientific EffectResistive heating: Joule Heating

Implementation Method 3

a carbon heater, which is generally used as the sheath heater 5 and the heater 6, is a grill heater that heats food inside the cavity 2 using a radiant heating method

Methodology Applied
Scientific EffectThermal radiation: Thermal Radiation

Data Source

PatentEP3405002B1Carbon composite composition and carbon heater manufactured using the same
Publication Date: 2024.07.17 LG ELECTRONICS INC
  • EP3405002B1 patent drawingFigure 1~2
  • EP3405002B1 patent drawingFigure 3~4
  • EP3405002B1 patent drawingFigure 5

AI summary

The present invention relates to a carbon composite composition for manufacturing a carbon heater used in a field of a heating apparatus such as an electric oven, and a carbon heater manufactured using the same. According to the present invention, there is provided a carbon composite composition including a phenolic resin as a binder, a lubricant and a base material determining a specific resistance of a resistance heating element at a high temperature, and the carbon composite composition may prevent a dielectric breakdown, a spark and plasma from occurring in a carbon heater, and improve radiation efficiency of the carbon heater.