Skin Effect and Proximity Effect
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- Опубликовано: 30 сен 2024
- #217 In this video I look at the basic effects that end up changing the resistance of conductors when signals of different frequency pass trough - skin effect and proximity effect. I look at the theoretical principles behind these phenomenon but also try measuring them in real life.
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It's refreshing to see this actually demonstrated for some real wire, rather than hand - waved over or, at best, just presented as a formula full of unknowns!
Its actually not that easy to show without proper tools, but its a fun experiment
@@FesZElectronics seeing how you managed to.use the tools at hand to nonetheless show a result that matched the model was also interesting :-)
I’m curious how flat conductors behave with high frequencies
I’ve made a couple of mag loop antennas using 1” x 1:16” aluminium strap. I haven’t put them up against the equivalent surface area of a tube.
They work well enough, but o was curious. Not a huge amount of information out there.
At 5:45, that is NOT true. Parallel currents ATTRACT and anti-parallel currents repel. Try it for yourself... or use the r.h.r. and the fact that like poles repel and opposite poles attract. The skin effect is an electromagnetic interaction -- it requires both E and B -- and the fact that these two are out of phase near a conductor... V=dPhi/dt.
From recollection Litz wire was used in many HF coils. Litz wire was very fine enamel coated strands bound together with delicate silk. It was often wound in a 'herring bone' looking pattern in RF chokes and IF transformers, not just a circular fashion.
0:20 the sovet MLT-1 (metal varnished heat-resistant 1W) 180Ohm resistor
Informative and fascinating explanation. Thank you very much.
Interesting, I have never considered the 'globular' distribution of current due to Proximity.
In a coil with both an AC component and a DC current, would the DC component act as a modulator of the AC resistance due to proximity effect?
So, does superposition hold? Or does my question lead to a non-linear results? The answer is probably fairly simple but I don't see it at the moment.
Disentangling heating from that sort of measurement would be 'interesting also,...
I had never thought the proximity effect can be so dominant. Would using litz wire also help in mitigating proximity effect to an extent?
"to an extent" :D from what I read, litz wire, and special coiling techniques like honeycomb/basket wound coils will help, but only in the
Depends very much on how you lay your windings in case of inductors for example.
Interesting exploration of proximity effect about which I have little prior knowledge. Skin effect I know well.
amazing
In the 196ties we built coils with RF stranded wires with silk cladding for high Q coils. Specialists wound the coils crisscross to reduce the proximity effect.
The coils were used for the intermediate frequency path in superhet ham radios for best selection properties.
Today I am fantasizing whether an improvement of Q would be possible with conductors (wires) consisting of copper/silver clad plastic fibres.
Anyhow as we did not have a VNA all this tinkering and the rules for best results was full of myths.
Great explanations.... I know you are more geared towards electronics, but the impedance from using large, stranded conductors for high voltage AC power transmission is one of the big limitations on how much current it can handle, know as line loss. As current increases, the impedance increases, heats the conductor and limits the conductors AC current carrying characteristics. Why sometimes when they convert an existing AC transmission line to DC, which does not suffer the same impedance related heating, it can carry more current for the same DC voltage over the same conductors. Since you just have the actual resistance of the conductor to worry about and no impedance losses.
The line's impedance should not be current dependent, only frequency dependent; whatever AC frequency is used, the impedance will be higher than the DC resistance, so the losses will be higher. Going for DC indirectly increases the current capability - the losses are smaller so the line heats up less.
@@FesZElectronics Correct, but when talking about large, stranded conductors, the higher the AC current the more impedance the line creates, due to the twists of the strands generating magnetic fields and fighting current flow. Just like you showed with a coil of wire, but this is strands in a large, stranded conductor. I'm a relay tech in substations and work with protective relays all the time. Take a look at a line distance relay protection scheme, also know as an impedance relay. It judges fault distance based on impedance and is calculated from the current and voltage, of course. And when the relay is set it can tell where along the line the fault actually occurred and if in it's zone, will trip. But as load increases, the impedance does in fact go up and line losses increase due to it.
Aside from an over current relay, that was one of the first forms of protection when the power industry started and still used today as a main source of transmission line protection.
And yes, depending on the system, 50 or 60Hz is a constant component in the impedance calculation.
@@FesZElectronics One more thing, on long, lightly or unloaded transmission lines the voltage at the receiving end actually goes up. We use shunt reactors to compensate for lightly loaded lines and of course shunt or series capacitors when the lines are loaded for voltage support. Look up transmission line series capacitor banks, super cool how they cancel out the inherent inductive impedance of the line and naturally vary the capacitance based on current flow. Again, using 50 or 60Hz as a constant the designer can decide on how much capacitance to add to cancel out the impedance and part of the equation is the expected range of current and voltage of the line.
Presumably the series resistance of the capacitor will also change with frequency. Would be interesting to know just how much it influences the circuit as tested.
Thank You
Suddenly I know why, "twisted shielded pair" has a reason to exist.
To avoid confusion, I would suggest using the correct term "impendance" when talking about the resistance of a component (or conductor) by doing a AC Measurement.
Measuring resistance by a DC Measurement is indeed still called 'resistance'.
Impedance has a resistive element and a reactive element. The demonstration is designed to explore just the resistance and to achieve that, tune the reactance out which happens at resonance. What is left is, or ought to be, pure resistance.
@thomasmaughan4798, thank you for explaining this so I wouldn't have to. Perfect explanation!
At 6:11 The direction of the force is opposite to what you have drawn.
Very good video. Thanks!
Great video. Thanks!
Great content as always👍🏻👍🏻👍🏻
I love your videos.
Nice! Where do you work?
'Electron1: can we go together. Electron2: keep distance
Electron1: Are you sure? Electron2: I'm positive; I don't really remember how this joke went though...
WOW... just the subject I was looking for. I REALLY want to learn about this. At this stage, it's like black magic, but hopefully with more of your videos like this one... I can be less intimidated. Thank You! and definitely subbed here!
unrelated to the subject, but...
it would be nice to see someone do a practical demonstration of "jacobs law". its basically impedance matching. but more motor/generator oriented.
that is, which one has the lower resistance, and how the current appears as torque, or heat...
lol, i tried making a video and the camera wont show the display on the variable load... sigh... meh, and i really need to make one with a few fets that can deal with more than 25W anyway...
Good video
the way that you say works with "ing" in them
the current to the conductor created the phenomenon.Ghost Wire,You should get a Ghost Signal.hahha
Iv figured out the lattice works the same way it not perfect like they say ,what would they do without Us,
there is Greater potential.
in everything,
guess what in that wire are energy pockets, sorry
I don't care.... I still hate CCA and CCS (copper clad aluminum and steel respect)
The error is in your head