- #1
Ana Mido
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Which is higher, the breakdown voltage if the electric field is uniform or the breakdown voltage if the electric field is non-uniform ?
Breakdown Voltage Depends on Field Uniformity?
- Thread starter Ana Mido
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- Field Uniformity Voltage
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Discussion Overview
The discussion revolves around the relationship between breakdown voltage and the uniformity of the electric field. Participants explore whether a uniform electric field leads to a higher breakdown voltage compared to a non-uniform field, considering theoretical models and real-world applications.
Discussion Character
- Debate/contested
- Technical explanation
- Conceptual clarification
Main Points Raised
- One participant questions whether the breakdown voltage is higher in uniform or non-uniform electric fields.
- Another participant suggests that breakdown voltage is a specific threshold value that is not inherently related to the uniformity of the electric field, noting that breakdown occurs where the field is strongest.
- A different viewpoint emphasizes that while simple models assume uniform fields, real-world scenarios often involve non-uniform fields, leading to complex breakdown phenomena.
- This participant also discusses the role of finite element analysis (FEA) simulations, which rely on uniformity within mesh elements, and the complications arising from material variability and chaotic behaviors in breakdown processes.
- Empirical data, such as Paschen's Law, is mentioned as a means to approximate the relationship between breakdown current and applied voltage, acknowledging the limitations of deterministic models.
Areas of Agreement / Disagreement
Participants express differing views on the relationship between breakdown voltage and electric field uniformity, indicating that no consensus has been reached on the topic.
Contextual Notes
The discussion highlights the complexity of modeling breakdown phenomena, including the influence of material defects and chaotic behaviors, which complicate the establishment of a straightforward relationship between breakdown voltage and electric field uniformity.
- #2
- 15,949
- 9,142
The question is a bit confusing. As I understand it, the breakdown voltage is a specific threshold value not related to what the field looks like. Of course a "real" field may be pretty close to uniform in a certain region of space, but may very well be non-uniform in some other region of space. As you increase the field everywhere, breakdown will occur where the field happens to be the strongest because that's where the threshold value will be reached first.
- #3
jsgruszynski
- 309
- 19
The simplest models of breakdown do assume uniform field but that's not necessarily what any reality actually is. Models are approximations for us stupid humans, not because reality must follow the model exactly.
This is where/why you can apply these ideals to a FEA simulation - within each mesh element, the assumption is exactly that kind of uniformity.
You can get some complicated results in reality and in an FEA simulation because there may be some parts (if physical aspects are well modeled) that will cause a small piece to breakdown and then cascade to more complicated breakdown phenomena like the fractal curves of a Litchtenberg figure. The problem is usually you don't know, and have no way to find out, the specific, small variations in the material that create weak spots for that lead to such things. There's also random processes involve that assure it might not happen the same way twice.
This requires FEA that can model that kind of variability per mesh element in the "proper way" (e.g. defects per cm^3 or similar). It gets complicated for physical phenomena where the act of something happening (e.g. conduction from point A to point B) itself changes the probability of some other subsequent things happening (e.g. conduction from point B to point C, B to D, B to E, B to F... B to ZZZZZ). This s the nature of fractal and chaotic behaviors - deterministic models and behaviors becomes the wrong question. Breakdown phenomena have this kind of effect which is why there is no simple algebraic formula for the relationship of breakdown current vs. applied voltage. Instead you have to rely on empirical data like Paschen Law which are still only approximate.
https://en.wikipedia.org/wiki/Lichtenberg_figure
https://en.wikipedia.org/wiki/Lightning_strike
https://en.wikipedia.org/wiki/Paschen's_law
This is where/why you can apply these ideals to a FEA simulation - within each mesh element, the assumption is exactly that kind of uniformity.
You can get some complicated results in reality and in an FEA simulation because there may be some parts (if physical aspects are well modeled) that will cause a small piece to breakdown and then cascade to more complicated breakdown phenomena like the fractal curves of a Litchtenberg figure. The problem is usually you don't know, and have no way to find out, the specific, small variations in the material that create weak spots for that lead to such things. There's also random processes involve that assure it might not happen the same way twice.
This requires FEA that can model that kind of variability per mesh element in the "proper way" (e.g. defects per cm^3 or similar). It gets complicated for physical phenomena where the act of something happening (e.g. conduction from point A to point B) itself changes the probability of some other subsequent things happening (e.g. conduction from point B to point C, B to D, B to E, B to F... B to ZZZZZ). This s the nature of fractal and chaotic behaviors - deterministic models and behaviors becomes the wrong question. Breakdown phenomena have this kind of effect which is why there is no simple algebraic formula for the relationship of breakdown current vs. applied voltage. Instead you have to rely on empirical data like Paschen Law which are still only approximate.
https://en.wikipedia.org/wiki/Lichtenberg_figure
https://en.wikipedia.org/wiki/Lightning_strike
https://en.wikipedia.org/wiki/Paschen's_law
- #4
Svein
Science Advisor
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