Film Capacitor Surface Roughness for Gas Release and Self-Healing
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Solution Overview
Problem
Film capacitors face challenges in maintaining high breakdown voltage and self-healing properties, particularly in regions where dielectric films adhere firmly, due to difficulties in gas release and surface friction resistance.
Innovation Solution
The film capacitor design incorporates a metal film with surface roughness variations in two directions, featuring a fractal dimension of 1.08 or more, and a heavy edge structure near external electrodes, enhancing slipperiness and gas release performance by creating irregularities and low-pressure areas for effective self-healing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the dielectric film surface is made rough to improve gas release performance, then gas release performance is improved, but surface friction resistance increases making film winding difficult
Solution Approach 1:
The patent applies local quality by creating surface roughness only in specific regions (insulation margin areas) where gas release is needed, while keeping other areas smooth for easy winding. The irregularities are localized to boundary regions between dielectric films rather than the entire surface.
Solution Approach 2:
The surface roughness is segmented into different regions with different characteristics. The insulation margin regions have increased roughness for gas release, while the central regions maintain smooth surfaces for easy handling and winding.
2Ease of operation
If the metal film surface is made rough to improve slipperiness, then slipperiness is improved, but surface friction resistance increases
Solution Approach 1:
The metal film surface roughness is applied locally at the insulation margins rather than uniformly across the entire surface. This localized roughness provides slipperiness where needed while minimizing overall friction resistance.
3Stability of the object's composition
If the dielectric films are made to adhere firmly to each other, then structural stability is improved, but gas release becomes difficult
Solution Approach 1:
The patent creates local irregularities at the boundaries between dielectric films in the insulation margin regions. These localized irregularities provide gas release pathways while the bulk of the dielectric films maintain firm adhesion for structural stability.
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 design improves the breakdown voltage and self-healing capabilities of film capacitors by reducing distortion and facilitating gas release, ensuring reliable operation in applications like electric vehicles and inverter systems.
Implementation Method 1
the metal film in the vicinity of the defect portion evaporates and spatters due to energy of the short circuit. A gas is produced when the metal film evaporates and spatters.
Implementation Method 2
Patent Literature 2 discloses that slipperiness of a film is improved by providing irregularities to the surface of the dielectric film and increasing the surface roughness, by which an effect of reducing surface friction resistance when a film capacitor is formed by winding the dielectric film with the metal film can be obtained.
Implementation Method 3
An average value of fractal dimensions of irregularity boundary lines due to wrinkles of the metal film is 1.08 or more
Data Source
AI summary
A film capacitor includes a main body portion and external electrodes. The main body portion includes a dielectric film and a metal film that is disposed on one surface of the dielectric film. The metal film has surface roughnesses of S1 and S2 where S1 denotes a surface roughness of the metal film in a first direction, and S2 denotes a surface roughness of the metal film in a second direction. The first direction is perpendicular to the second direction. S1 is greater than S2. The main body portion includes a pair of ends in the first direction thereof. The external electrodes are disposed on the pair of ends in the first direction of the main body portion, respectively. An average value of fractal dimensions of irregularity boundary lines due to wrinkles of the metal film is 1.08 or more.