AC versus DC load breaking comparison with a knife switch
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- Опубліковано 8 вер 2024
- Difference in electrical contact by alternating current to direct current. The four resistors are wire chrome 650x4 = 2600 watts.
Note: The voltage of 220V rectified is about 311V, but under load it drops to approximately 213-209 volts.
Woah that's a cool experiment, I knew DC arcs were worse but I did not realize the extent. This is why higher voltage DC breakers/switches/relays are so much harder to find and typically more expensive too.
Wow... excellent demo on why I won't be using an AC relay for my battery bank
Breakers for DC current are specially designed to interrupt the arc internally. Great demonstration for a benefit of AC power, the waveform crosses 0V, fifty times per second, which clears the arc.
Hey, where r u from? Here in Brazil we use 60 Hz
This is important, so many is now constructing 24v and 48V DC systems with 200 - 400A and more using switches and breakers meant for AC at the AC rated limits not knowing they are creating a fire hazard...
dc low voltage hi amp=safe
dc low amp hi voltage=💥
thanks a lot - very informative demonstration; now i know that I must be VERY cautious with my 100V+x DC solar panels ;-)
Yes, 100 volts DC is no joke, take care ;)
@@ElectricExperimentsRobert33 anything above 60 VDC is to be taken SERIOUSLY!
Nice setup and probably the best demo of the difference between AC and DC I've seen (30 or so years in Electronics!) Thanks!
now I clearly understood why AC switches clearly marks '230v AC only' I always wondered
dc low voltage hi amp=safe(no spark)
dc hi voltage low amp=spark plug💥
finally, i found this video again. Thanks for share this incredible demonstration
This video learned me why you don’t use ac relays for dc applications.
Use a transistor instead.
You can use an ac relay it just has to be derated appropriately for dc use.
@@stevelee9924 generally speaking, most AC-rated breakers/switches/relays are rated to 32vDC, but no more ;-)
This video deserves a lot more views, it's a really excellent demonstration, anyone thinking of using AC breakers on DC should watch this.
As always your video's are simple, to the point and highly enjoyable for the thinking person
One of the many reasons AC won out and DC was not used for home electricity.
Love the arching! Reminds me of my childhood and some of my first electrocutions... :D
Excellent demonstration, thank you.
With those capacitors across the DC line, the resulting voltage was considerably higher than the AC voltage, as seen in how much more quickly the elements heated up. Still, a very good demonstration.
The capacitors were put there so the demonstration was with DC, not pulsating DC. Have the remember that the key difference in arc breaking is that with AC, the arc breaks every half cycle and have to reestablish itself either 100, or 120 times per second (depending upon the standard used in your country). With DC, there is no zero crossing and hence the arc only breaks when the distance becomes too large.
That's a good observation, the heaters warmed up faster with DC, and the actual power going through those heaters was almost _twice_ the power with AC.
Hmm. Looking again at the video, are those 4 resistors actually coils of nichrome wire? If that's the case, then they probably have quite a bit of inductance which tends to limit the flow of alternating current. And a lower resistance to DC would tend to cause them to heat up quicker when powered by DC.
@@johncochran8497 Even if they WERE coils or wire, there was no iron core within the coils (thus 'air coils') so any inductive effect is almost negligible. They are, for all intents and purposes, a resistive load, and thus will respond to the AC or DC voltage equally, as any resistor would respond.
Great demonstration - as an old electrical/electronics engineer I’ve know about this but have never seen it in real-time only the after effects!
Excellent video. Great demo of showing why DC current is so hard to break. and the extra heat in the heating elements.
An extremely simple and effective demonstration for DC Currents tendency to continue flowing by jumping the air gap when suddenly disconnected.
This makes it clear why you need specially designed breakers that employ an extinguishing chamber to handle the subsequent electrical arc when the contacts suddenly separate from a trip event.
This also makes it clear why there are so many EV fires. They are sitting at 400VDC with no means of arc protection. They are relying on high voltage interlocks to get broken and the BMS shutting off voltage.
Turns out however that fuel burning vehicles are still statistically more likely to catch fire.
@@japerelectronics2568 Proportionally there are much less EV fires compared to vehicles using a combustion engine. It only that they are more "exposed" in the media.
The real danger is that EV fire is much harder to extinguish.
@@ppdanthere are MILLIONS of ICE vehicles, and just thousands of EV's. Statistically, EV's are more dangerous.
@@Sanwizard1 Statistically EV's are less likely to catch fire (Google it, they are up to 20 times less likely to catch fire).
The big problem is that they are a pain in the ass to extinguish. Where a burning ICE vehicle can be extinguished with a simple fire extinguisher this isn't true for an EV since it will catch fire over and over until all energy in the main battery has been completely depleted (unless the fire had nothing to do with the main battery)
I'm watching all your videos AGAIN today! They never get boring! Excellent work sir! S
This verifies an experience I observed. The problem was that it was no accident.
I was watching my mechnic work on my car. He grounded a wire that seemed to explode and started a fire.
He should have known better that is why I say it was no accident.
But it impressed me and most likely saved me from doing the same thing now that I am learning about wiring
up to use PV Solar Power.
This video speaks loudly about safety issues and training needed by anyone using electricity,
and especially high voltage DC Current.
I want to be safe, this is why I happened to find your video.
Thank You for posting.
Despite the voltage discrepancy, I think this is a great quick video to showcase AC having a lower tendency to arc. Regardless of voltage, AC crossing zero potential each half cycle is something that can be used to explain why it is used in a home over DC. Also why much higher AC voltages can be used for transmission more safely. HVDC has made inroads in some transmission lines, as there are technically lower losses from the lack of eddy currents (I think), but overall I really appreciate this video. Look forward to a detailed correction of why some hydro plants and other HVDC links exist.
A super slow motion of that arc would be amazing!
Yeah... DC has a much higher arc potential and inductors have back feed even on DC especially at higher voltages.
It's true. I made DC arcs at 230V using FULL BRIDGE REKTIFIAH!
"It turns out that trying to sustain this big an arc makes the FULL BRIDGE RECTIFIAH run very hot, let's see how long it actually can before burning out" *proceeds experiment until the rectifier goes out with a flash and a bang* :P.
What's most impressive is that such a big arc can be sustained on a relatively low voltage such as 220Vdc.
That's why it is earsier to start and maintain an arc with a DC vs AC welder.
THANKS for the GRAPHIC Demonstration
COOP
the WiSeNhEiMeR from Richmond, INDIANA
...
If you rectified and smoothed 220V AC to get DC, that would have been 311V DC
That's a very interesting demonstration! Thank you.
AC crosses zero volts 100-120 times per second. DC has no zero crossing, the capacitors near the rectifier make sure of that. Without zero crossing, that knife switch could arc until it glows, just like those heater elements, if not opened more than ~10mm.
The DC voltage in this experiment is not 220V as stated.
When the AC is 220V RMS and if this is rectified in a bridge and (big) capacitors added, then the unloaded DC voltage is close to sqrt(2) * 220V or 311V.
The power dissipated in the 'DC' position is therefore substantially larger than in 'AC'. This is why the resistors start to glow much faster with DC.
But a nice demonstration anyhow.
The precise voltage in this experiments is 308 volts, in the video I have not specified it because not all people understand that the alternating current is rectified when the voltage increases.
+TechsAndStuff You are all referring to the peak voltage after rectification & that will be true at no load, but if you're drawing 8 or so amps from 1000uF, the AVERAGE and RMS voltage will sag, as the capacitor discharges between half-cycle peaks... This is easy to see on an oscilloscope. If 308 is an actual measured voltage, I'm surprised it isn't lower... Nice arc though, and I might also show it to some people I know who think it's a good idea to use cheap domestic ac circuit breakers on DC solar/battery circuits.
The tension of 220V rectified is about 311V, but under load it drops to approximately 213-209 volts.
DC is still used today, by travelling Showmen for dodgems, Waltzer etc.
Its superb for controlling motor speeds, and they use 110v dc, with machines including their lighting, drawing around 275amps.
Lots of arcs from their knife switches!
🤣🤣😂
Wow! I didn't expect that DC load breaking make such fat arcs, even on a resistive load! Impressive!
And that's why electric cars use a 12V subsystem to run things like the lights, fan motors, window heaters and such. If they were to pipe the 350VDC from the traction battery into the car to power these things, each switch would have to be super beefy to handle the arcing. So they just use 12V like regular cars, and use a DC-DC converter to keep the small 12V battery charged from the main traction battery.
Switchmode power supplies switches at 350v on the primary and the transistors are not super beefy, they are indeed small because of the small current, thanks to the high voltage. Powering a LED headlight with 350v would not be a problem for the switches, but 12v is the standard for lights, fans and some motors for the car subsystem. Convert 350v to 12v is cheap, otherwise, you would have to build all the parts again for 350v.
That is the silliest conclusion you could ever draw from this
@@Ferraday He is not fully wrong. I worked on 42VDC systems in the late 90's and they ended up stopping it over arcing. Every loose terminal or broken wire was a fire risk at 42VDC. I say he is not fully wrong because the real reason is probably because 350VDC is crazy dangerous to even touch. You would be a mad man to put 350VDC anywhere near where someone could be exposed to it.
@@osmargarnica and consider what to do, when transistor go short. In AC powered power supplies tiny glass 5x20mm fuse at AC side is OK, but if your source of power is 350V DC battery, things are getting problematic.
There's probably a different way to get those voltages, because from most electric cars I know that the battery pack has a couple of taps, one for the user operated equipment like lights and fans, and one for the actual traction, simply by tapping off a smaller amount of cells than the total traction side does.
Fairly sure there's absolutely no DC-DC conversion happening to keep a second battery charged, because that would bring losses, and add weight and a second battery to an already expensive battery pack in a car.
if you got the 220AC and put it through a rectifier you actually have about 310V since the AC measurement is RMS and DC is peak to peak.
In 220 AC the voltage also bounces between +310V and -310V. But it is not a consistent voltage, it bounces back and forth 50 times a second, each time going through zero, where there is no current at all. So the overall current is much lower, actually should be the same as in 220 DC, but NOT at 310V DC. This is why the heating elements get much hotter on DC, you can clearly see it in the video.
All you did was explain AC VS DC in heating elements.
This bring back memories when I had an intern short circuit a string of 15 solar panels. He went to plug in the male homerun to the female thinking it was a jumper. Plasma arc flash blast to the face!
Awsome video !!!! AC is a jiggle, DC is all the electrons going one way. Once they are moving enmass they have tremendous force. Like large volume of water moving in a large pipe, it does not want to stop! Look into long wire DC, many unique affects. Some of Ed Leedskain technology employed very slow AC, which has DC properties. He also used resistive coils to make electrons move.
Clay
aaaflooddrying Yes, in fact it is exactly as you say :) You can see my other video in high voltage DC:High Voltage DC 1400V 1.2A
Electrons all going the same way is not why it arcs. With DC the potential (voltage) is constantly across the knife junction, with AC the potential drops to zero every 120th of a second......therefore the arc can't continue across the gap.
Just read down, Engineer 21261 is saying the same thing.
Spectuclar. A picture says a thousand words.
Would have been great had you been able to adjust the DC voltage to show arc break length at different voltages.
Made teaching media for lectures very well.
AC goes trough 0 and therefore is easy to disconnect.
Do NOT try this at home, if you don't know about protection and insulation.. Very nice video by the way..
Wonderful demonstration
There may be more current flowing on DC because the heating coils will have a greater impedance on AC from the inductive reactance, but on DC it is purely resistive.
This is marginal at 50 or 60 Hz. This effect is mostly due to the fact that 220V AC after rectification has higher mean voltage - 310V without load and under load it depends on how much capacitance is attached to the circuit, plus other factors that determine how fast those capacitors can charge. With lots of capacitors and beefy diode nad AC source you can get close to that 310V.
Not true
Nice! I was playing with 560VDC made from PFC, putting it through 2 in series 25W / 230V light bulbs. Arc was longer then 1cm but not so thick as yours.
thanks very much, clear video
the AC current drops to zero on each half cycle this helps to quench the Arc, on DC this does not occur hence the persistant power arc on circuit breaking
If you use graphite electrodes, you won't be able to break AC current of 10A or more without arcing. I've done some experiments with it and recorded a few good video examples, just for show. All of them you can find on my channel ;)
Now i know why they don't use Direct Current in houses, there are more chances of it catching fire if there is a short circuit, cause of the arcing danger!.
From same supply in AC voltage , DC = 2√ 2 in the bridge rectifier if in the full wave rectifire = √ 2 , in the half wave retifire some 0.7 x AC. , Si saturation 0.7 Volt. if sure must be measurement by Osiloscope referent input AC. vs AC. output vs DC. output for look wavefrom amplitude vs. time sir.
It's interesting to see this, as I have seen written on switches before now: "A.C. ONLY" Now I know why this is! :-O
Thanks for showing,
-BBD.
a demonstration .... enlightening!
There is a brief moment during an AC cycle where there is 0 volts as the current changes direction. Obviously with DC you don't get that so the arc is a lot harder to interrupt!
I like that red soft light when you flip the switch.
You gotta do some about that arcing thou
In short: Tesla's AC vs Edison's DC, and that's one of many reasons that we still use AC today...
Wow, very intersting ! I. Like demonstration 👏👏👏👏👏👏
I was not expecting that. Excellent vid!
Can anyone explain whats happening with the DC im just started learning about current and circuits today specifically DC
well, DC has a constant value so when you disconnect it you have the full value of the voltage across the switch which causes the arc, while in AC, the voltage and current are alternating as its name implies so they pass though zero point with high frequency so you are very likely to disconnect it at zero or very little voltage which can't cause an arc, even if you were so unlucky that you disconnected at peak voltage it will go through zero point in just few milliseconds so the arc won't have a chance to continue.
hope that helped you .. if you need any further clarification I'll be more than happy to help.
@@gebro7000 Gdy zmienisz podłączenie jednego przewodu z prostownika Graetza (kiedy prąd płynie w kierunku dodatnim) na zasilanie prądem zmiennym to wówczas prąd jest prostowany połówkowo i przy rozłączaniu powstaje łuk.
Ahmed's answer is basically correct. The breakdown field of dry air is about 10,000 V/cm. In the DC case, 220 V will arc over distances of 220/10,000 = 0.022 cm or less. So, why does it arc at longer distances? The arc is a plasma and so is quite conductive. Once the plasma is established, you gradually grow the plasma distance by opening the switch. So, if you opened the switch even 0.5 mm and then connected the dc, there would be no arc. With ac, you can still get an arc over 0.022 cm, but it is intermittent. As a result the arc cannot grow as you open the switch.
I.E. If we connect the circuit in DC , the breaking current is greater than AC configuration.
Jose Mota
Oporto-Portugal-
I tried to explained the difference of AC & DC switches to a Radio Shack employee, and he was amazed... Then his supervisor said I was wrong... I left the ignorant there, but I'll give him this link next time so he learn not to play with DC!
He was gran-gran-gran- son of Thomas Edison , probably
These heat tubes, what is their construction and what are they made from? Maybe their inductive reactance (to the alternative current) is so big, that the current is much lower in the scheme? If these heat elements have very little resistance to DC, then you actually has a short circuit and amperage goes very high and you get plasma arcs.
If you smooth and rectifie mains , you can pull arcs like that :P
Is truck generator is not better? for the larger generator which is all the more power you get .. not sure that there is enough wind always .. in fact why I want more batteries. so there is always enough power on one of the batteries .. will be destroyed if the generator blades get stuck?
Add a capacitor parallel to the load and try it again.
What will happen?
@@rishabraina2467 the ark will extinguish easier.
to the load or to the switch?
@@haczyk84 Load.
@@TheOriginalEviltech In a pinch, you could put the capacitor across the breaker--this will render arcing nearly impossible. Simply put, when the breaker opens up, it will have almost zero voltage potential across it (due to the capacitor). The capacitor will quickly charge up (via the load) and then the full potential will be across the breaker.
It's interesting to see this, as I have seen written on switches before now: "A.C. ONLY" Now I know why this is! :-O
-BBD.
And to think Edison wanted a DC transmission and distribution grid. Thank goodness Nicolai Tesla was smart enough to tell Edison "I quit" and push for our AC transmission and distribution that we have today.
DC doesn't travel as far
@@TheMrR9 AC and DC have about the exact same voltage drop for a set distance from the source and based on internal resistance of the conductor material. The primary advantage of AC over DC is the ease and relative simple method for changing voltage. AC uses transformers to step voltage up or down through AC's expanding and collapsing electromagnetic field. This means an electric plant can easily produce power at around 24kV phase to phase from its generator, but will need to step this voltage up to very high levels, anywhere from around 100 to 525kV, through transformers to send it out to the transmission grid to reach across very long distances. From there, transformers can be used again to drop the voltage to the distribution grid, normally around 4 to 15KV, to supply cities and towns. To drop the voltage so the end users (you and I) can use it, transformers are once again used to lower the distribution voltages to safely power the customer's equipment, normally 120/240 v single phase for residential or 120/208v or 277/480v poly phase for commercial customers.
While DC voltages can also be increased or decreased, it's far more complicated and expensive to do so.
They are actually beginning to install DC mains transmission infrastructure in some parts of the world now. Very interesting how it's done.
They do use DC transmission here in Brazil.
DC is more economical than AC past a few hundred miles. This is why there are quite a few long-distance high voltage DC transmission lines all over the world, including in the U.S.. And has been for decades. DC is also significantly more efficient in terms of power loss over long wires.
AC is more convenient for shorter distances and when voltages need to be stepped up and stepped down. So AC is pretty much universally used for utility distribution. People are used to working with AC because the DC is kinda hidden in the backbone. But it is still very much a part of many grids. California has a huge DC line running down the whole state, for example.
DC house wiring is actually a thing. These days it is done using POE+ or POE++ (power over ethernet), which uses roughly a 56VDC actively-monitored, isolated standard to run power over ethernet cables. Very much a thing. My own house has POE+ cabling all over the place for the wifi routers and security system.
Low voltage DC wiring for outdoors has been around for 50+ years. High voltage DC (e.g. up to around 350VDC) for outdoor LED lighting is also a thing. These sorts of DC power supplies tend to be isolated and current-limited, which means there is no current-return path through the ground, which makes them very safe.
-Matt
is this because the AC is sine and the pulsed DC is more of a square? or maybe because of a higher ion concentration in the breakdown?
nice demonstration!
Wow! I am surprised that 220 VDC can produce such a big arc!
Rectifying the output of a 2kV MOT would be fun :)
that's essentially what microwave ovens do, the magnetron acts exactly like a triode tube valve only letting electricity flow from the heated filament to the plate in one direction only
Very clear show. Anyone knows some source comparing AC vs DC ratings for contacts?. I.e. if you know that a contact is for AC 240V X Amps, how much DC (aprox.) could it cut safely?
now where's that con artist thomas edison
tesla is my hero. edison was a hack
that cuz that 230 volts has helluva current on it !
i expected arcs on dc but holy shit those are big
hello would like to know the connection diagram and what materials are needed to make one ... very good videos, grateful, when you can answer me thanks
And this proves that Tesla's idea of Alternating Current was far better than Edison's idea of Direct Current. If it wasn't for Tesla, light switches and contactors would have to be way more beefy thus being much more expensive. Thank goodness he came along.
Hi Robert great demonstration of the difference breaking AC current vs DC current. I am a teacher and I would like to make a similar setup to demonstrate this in my classes. would you care to share what items you have used?
I don't know what you teach but I would recommend against working with voltages this high unless you know what you are doing. Regardless the resistors would need to be about 19 Ohm total to dissipate the full 2600W. Looks like they are probably four 5 Ohm resistors in series with each other. Other than that you just need the knife switch in series with the resistors and the two power supplies.
Recommend against working with such voltage.... 220V AC is all around us, now the DC current is what we should do with caution but it's a demonstration and an isolated system so it's alright.
I forgot to make mention about the Lenz law. Is that so, or I´m mistaken?
Why the arc still happens in DC with a pure resistive load? I tought the main cause of the electric arcs were the induction effect.
NO! Let us say that you have to study more about electrical arc discharge. The arc is much more stable in DC due to it never pass (never comes) to zero, voltage and current as well. Look also to the electric welding subject. You will find the same.
Great video. Had a noob question though. Nowadays, there are more gadgets that work on DC than AC. Even seen fans and air conditioners etc that work on low DC voltages. So why not transmit in HVDC and buck down the DC. Are bucking and boosting problematic as well? Or is it just that existing grids need to be replaced thats preventing widespread adoption of DC transmissions?
+James Highland High
Voltage Direct Current, is a system of transmission of electrical
energy in direct current instead of alternating current as is most
frequently used. This
system takes advantage if used over long transmission distances and
with direct lines, the system in fact has less dispersion of an
alternating current power transmission over long distances and in the
form of a single line, without branches and transformations. On short distances, and on the distribution networks, it is not
convenient, since the high cost of the transformation from current to
alternating does not offset the benefits.
As it is known, in fact, the distribution of the electrical energy is
practiced almost completely into alternating current for its easy
transformability in various voltages and for the advantages of the use
of the three-phase transmission.
Due to its characteristics of linear transmission over long distances,
HVDC direct current is transmitted through overhead lines or submarine
cables.
Typically, the power of an HVDC transmission system is larger than 100
MW and is usually comprised in the range between 1000-3000 MW.
The major disadvantage of this type of technology is that it requires conversion stations that prove to be very expensive.
Thx, great demo :)
You can hear how the arc creates frequencies. Is it pulsed DC?
Yes, DC.
Clearly it's pulsed. True DC arc makes no sound at all.
@@BenHutchinson321 Indeed. With a 2600W load at 220V DC the current is near 11A. That would make not such large arcs. I guess since the rectifier is breaking the current through the ionised air 100 / 120 times a second and the small induction is ramping up the voltage over the knife switch, creating a new current flow and the audible sparks.
The capacitor bank don't allow the rectified DC cross zero volt, there's *no interruption* !
Very Good !
hello, I would like to understand how you make the switch between AC and DC with the rectifier without putting AC in the DC capacitors? Thank you
High voltage rock 'n' roll
It's not high voltage, it's just mains voltage
I found this video by looking up knife switches. Although you are using a glove, I would take more precaution by adding a non-conductor to the top of the knife switch. How do you know what voltages and how much current the Glove can attenuate...just a thought...The video was interested.
36/5000
The gloves are isolated up to 300V ;)
There is nothing divine, as good exists only in the brains of the believers, a collective hallucination. Otherwise you probably need to take your pills regularly and you definitely have no idea about electrical engineering.
Typo correction: "good" should be "god"
Dude, a whole DC grid would only have been possible if they had access to modern semiconductors like Thyristors & IGBTs (which came at the end of the last century).
Now, staying with 120V was a mistake. I don't say it would have been easily possible to transition to 230V, but lower cable sections would have loosened the tension on the copper market, and reduced construction prices.
DC 220 has flame,I think copper coil of the rotor inside.
I would like to have known the Amps ????? Just like a welder the bigger the amps the bigger the arc !!!! Was the Amps the same in each circuit .....
In description there is 2600Watts in resistors, so it will be like 10A
The voltage and load is about the same. So Amps are the same too.
@@volodymyrzakolodyazhny7740 DC has higher voltage because of the capacitor filtration
And that fuckin' humongous arc is at only ~13A DC @ 210V. Unbelievable! I must admit this video makes me a bit tempted to try and disconnect my battery bank without the arc suppressor when it's delivering around 200A! But then again, I'm only slightly tempted. Okay, slightly more than tempted I must admit. Ok, fuck it. Video @ my channel in a few days unless I die or something!! 😁😁👍
No video on your channel, so I guess you died.
Rip
Rest in power sir your sacrifice was needed to keep us safe
Just DC arced myself with 48volt solar system. Building the battery cabinet and accidentally direct shorted one string. 1000 amps at 48+ Vdc. Melted the terminal right of the cable. But the flash gave me 2nd and 3rd degree burns on all 4 finger on one hand and 3rd degree on my other hands thumb. I work with 480vac everyday. I know my PPE. Arc flash clothes cat2, gloves, balaclava u name it. So I just got careless and tired at 1 am trying to get some stuff done while the kids slept. Been three weeks and I've got use of most of my fingers except my index to on my right and thumb on my left. Still too leathery to bend. Few more weeks. My brother works in a burn unit and checked me out. He confirmed the severity. Got me some silverdine ointment which is helping shed the dead leather skin. Point is Don't get comfortable with DC just cause it's seams like low voltage. Welding is only 24v at 50 amps just saying.
@@electromechanicalstuff2602 thanks for sharing, its important to point out dangers of solar panels. In Norway there are far too many unskilled people working with solar panels. Im afraid this is going to cause a lot of accidents.
y por que sucede que la corriente directa hace arco voltaico y en cambio con la corriente alterna no se produce dicho arco
hi i have a question.
so engineer21261 said "the AC current drops to zero on each half cycle this helps to quench the Arc"
now if i have 220 AC and use a bridge rectifier but NO capacitors to smoothen out the wave. i have 120Hz DC. so the DC also drops to zero each half cycle.
does this help to quench the Arc? can i safely use a 220V AC rated switch ?
CamperPolice The only rectified current is not sufficient to be continuous, it takes a capacitor of at least 1000 MF- 400 volts work.
It might, but I wouldn't count on it, for safety reasons. Also, since there would be a large AC component, any significant inductance would tend to keep the current flowing past the zero point, and any capacitance would prop up the voltage.
Could you pls advise me about item list for this testing?
Could you please tell me, Where can I get these resistors? All I´ve found till now are pure resistive loads. Nice video by the way, very instructive.
www.ebay.it/itm/Resistenza-candela-ricambio-per-stufetta-elettrica-steatite-600w-30-cm/202657656309?hash=item2f2f566df5:g:uZYAAOSwo4pYZVCb
All resistors are "pure resistive loads" .... that's the whole point of them LOL.
You can use small heaters as low cost resistive loads. Most have 2 circuits for "high and low" power.
EDIT TO CLARIFY: See comments below regarding resistive and inductive effects of resistors. In this simple test the inductive effects are irrelevant and any suitably rated resistor would do.
John Coops That is largely true, but not entirely accurate as common wire-wound resistors may also have inductance if they are not specifically constructed with a counter-winding to cancel out the inductance (which is a special type of “noninductive” wire-wound resistor). Though at 50/60Hz that inductance is of very little concern as it is minimally reactive at such low frequencies, it can become increasingly problematic at higher frequencies (and especially at RF). Thanks for the link to this video as it is indeed an excellent example of the added challenge of quenching DC arcs.
@@ethanpoole3443 - yes, you are correct that wire-wound resistors do have a certain inductive element. My short reply above was only relating to *THIS* application, which is simply to provide a load onto a 50/60 Hz circuit to shown the effects of switching. Furthermore, the main demonstration is about switching a DC load where the inductive aspect is not relevant.
hi .. if I have a generator of a car. can I get power from it through the wind. and it may well charge many batteries? in the sense that there is always flow in one of the batteries
yes yes .. What I mean is. can you get the free electricity out of this one? For example, a house must be shown to have 20 amp .. so how many batteries you need to reach as many amps? and you get ever so many amps out of this one. ?
Why the heating elements get hotter on DC than on AC? I think you pump much more current there, that's why the arc is showing up.
It's the basis of AC versus DC! AC is a sine wave, so the current rises & falls 50 (or 60) times per second for the given AC RMS voltage. DC is continuous voltage AND current - there is no 'resting' period - so the net power delivered is higher for the same voltage & current (this is first year basic electrical student knowledge).
Hi! I've a question. If I'm right, the spark is due to air ionizing due to high voltage. What happens if this experiment is conducted inside a vacuum instead?
In the absence of air the discharge increases in length.
I believe you are right here, but it buggs my mind: What carries the current in the absence of air? An electric arc is a plasma, right? A plasma means that there has to be matter (air for example) that can be ionized.
So my conclusion would be: No air, means no matter that can be ionized. What results in no electric arcs.
What do I do wrong, or what do I forget?
That's true but sometimes an electric arc can happen under high vacuum. One way can be extremely high voltage, that makes an electric field strong enough to make electrons jump out between two conductors at high potential however you need extremely high voltages, and that can be mitigated avoiding sharp points and using equipotential rings/electrodes.
Another way with circumstances similar to the ones of this video is when you have an very high current and sufficient high voltage and you separate two conductors, some of the contact surface can vaporize and that can sustain the electric arc which in turn will vaporize more metal. Metal plasmas have very low resistance. Vacuum switches exist but they have some special design parameters to avoid electric arcs, also x-rays!
Wrong. In low pressure air, length increases. In a vacuum though, there is no air to ionize. As such, an electron beam would need to form instead, but 220v is too low to form an electron beam across that large of a gap. You'd need a few thousand volts to create that electron beam.
Nice video!
What are the output impedances of the two circuits? Are you comparing apples to oranges?
This is all fine. For high current.
But what about low voltage, low current DC? Say for example 12V 1A DC. Would it be ok to use a 1A AC circuit breaker then?
I would say yes.
The lower DC voltage would not produce such a large arc, but the effect still exists. Every time the DC circuit is opened, it runs the risk of arc (and possible NOT breaking the circuit). If you feel you must use an AC device in a DC application (not recommended), at least size the device for 3-10x the rated DC current, so that the arcing will not destroy the metal contacts as quickly.
@@edinfific2576 The answer should be NO! See me response below.
@@d3kzh : 12V is a very low voltage and arcing is not that much of a problem. Normally, switches rated for 240Vac are also rated for 24VDC. Arcing does not pose a significant problem until your voltage goes over around 50V.
Serious arcing starts occuring around 100VDC and 1A of current. Below that level, there is not enough energy in the arc to maintain it.
1 amp at 12v is not capable if sustaining an arc. Doesn't matteer if AC or DC.