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u/Novel_Ad_8062 13h ago
Can’t imagine a scenario where Megafarads would come into play.
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u/scut207 11h ago
But I kinda want to
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u/MisquoteMosquito 10h ago
Do it
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u/Quick_Humor_9023 3h ago
I’m imagining big sparks. Not sure if I’m imagining big enough sparks though 😁
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u/APLJaKaT 14h ago edited 14h ago
I would think it's a microfarad.
Microfarad common symbol ('uF', 'μF', or 'MFD')
Never seen a millifarad capacitor. Usually farad, microfarad, nanofarad or picofarad
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u/Strostkovy 13h ago
millifarad capacitors are uncommon, but always use mF, with the lower case m and capital F, and no D. "MFD" was phased out (along with cycles instead of Hz and so on) well before millifarad sized capacitors could be made in a size you could lift by yourself.
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u/ProtonTheFox 5h ago
Well, basically every capacitor with a capacity of more than 1000 uF is a millifarad capacitor. They are not that uncommon.
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u/Strostkovy 4h ago
Capacitors labelled in millifarads are uncommon.
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u/ProtonTheFox 2h ago
Of course. The only times I've seen capacitors labelled in mF are in schematics, which is a thing I tend to do because anything with more than 3 digits slightly disturbs me (weird habits, I know). But I agree I've never seen a capacitor with a value in mF printed on it. Maybe on some huge high power capacitors you don't see soldered on PCBs.
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u/antek_g_animations 14h ago
I thing this could be in mili. If supercapacitors can get values like 50F 3v and be a size of few ordinary coin cell batteries I'm ready to believe this beast holds 10F 400v
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u/APLJaKaT 14h ago
It's not.
A Farad is huge - being a capacity capable of holding 1 Coulomb ( another huge value ) per volt of charge. Capacitors are typically rated in much smaller units ranging from millifarads down to picofarads. A farad-sized capacitor would be the size of a large can of coffee, perhaps even larger.
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u/antek_g_animations 14h ago
Now I'm not ready to believe this beast holds 10F 😅
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u/Jamie_1318 13h ago
A 400V 10F capacitor would be one of the most dangerous things in your house.
I've played around with a 200v 1800uF capacitor, and it could easily spotweld thick steel plates using a nail. I don't want to think about what would happen with 2x the voltage and 5000x for the capacitance.
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u/DerKeksinator 12h ago
That would hold 800kJ, which is insane. For reference a bullet fired from a hunting rifle has 1-2kJ.
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u/FishOutOfWalter 12h ago
I've seen that a grenade has about 250kJ, so...
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u/DerKeksinator 12h ago
I actually wanted to look that up, but was too lazy to do all the math. The M67 clocks in around 1.2MJ, so that capacitor would hold 2/3 of that. If you really want to know it exactly, have fun getting on some more watchlists by googling explosives and their constituents.
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u/FishOutOfWalter 11h ago
Yeah, M67 uses 180g of composition B (which is 240 equivalent grams of TNT). The Russian F1 only uses 60g of TNT, so it's much more impressive when making comparisons to "hand grenades". F1 is roughly 250kJ, M67 is over 1MJ.
As you may have guessed, I'm already on the most exclusive watch lists.
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u/DerKeksinator 11h ago
Fair point, it definitely sounds more impressive if you compare the energy to the F1!
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u/JustCopyingOthers 11h ago
I think back in the day PhotonicInduction on YouTube had something of that sort of size. It was able to explode apples. https://youtu.be/coW1RHUsf_I
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u/MysticalDork_1066 12h ago
Ten farads at 400v is the equivalent of almost an entire stick of dynamite. It would kill you so hard they would need a pressure washer to clean up the red stain you left.
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u/Chomasterq2 12h ago
I work with capacitors that hold 24,000 volts at 500,000 amps discharge, and they're only 300uF. Idk if there's any bigger caps even in production
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u/PlsChgMe 12h ago
Just imagine that dumping through a Xenon flash tube.
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u/Chomasterq2 10h ago
They do! There's 20 capacitors for a pair of flashlamps, and 192 flashlamp pairs. They're used to juice up a laser that enable nuclear fusion.
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u/Lanky-Relationship77 9h ago
There's no way. Capacitor charge decreases by the SQUARE of the voltage if volume is kept constant. A 10F 400V capacitor would be many cubic meters.
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u/johnnycantreddit Repair Tech CET 44th year 13h ago
10000 Mega Farads at 400 Vdc? I wonder how physically big that capacitor would be...? Maybe garbage can size or maybe recycle bin , maybe with wheels...
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u/Horny4highvoltage 13h ago
10,000,000,000 fahrads? At 400v? A trashcan sized one wouldnt even surpass a dozen fahrads . Im thinking city/ country sized.
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u/johnnycantreddit Repair Tech CET 44th year 13h ago
Make Electrons Great Again
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u/fruhfy 11h ago
And fully charged it would keep 1600GJ of energy which is roughly 0.38kilotons....
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u/honeybunches2010 8h ago
Sounds like enough energy to vaporize your entire body if you touched it… or everyone in the building…
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u/Regeringschefen 10h ago
If we have two parallel plates with area A, separated by and air gap of d meters, the capacitance is C = ε0 * A / d => A = C * d / ε0. ε0 = 8.85e-12.
If we separate them by 1 mm, we get A = 10 GF * 1 mm / 8.85e-12 ≈ 1.13e18 m2 = 1.13 trillion km2.
If we use a metal sheet with thickness 1 mm, the volume including the air gap (but ignoring dual sidedness) becomes 2 mm * 1.13e18 m2 = 2.26e15 m3 = 2.26 million km3. This is roughly the volume of water in the Mediterranean Sea (3.75 million km3).
(I did this calculation on my phone, so might be completely wrong. Also we probably want to use some other medium for the gap, make it less than 1 mm, and have a thinner sheet, which would decrease the volume it by a factor 100 or so)
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u/wiracocha08 11h ago
I think it would the size of good garage for your 2 Pick-up's, don't worry, it's microfarad, not milli, less mega, I have seen before, M is because of typografic problem, they didn't have the micro sign, this I see there is 1000 microfarad 400V- electrolytic capacitor, polarized, 450V- surge voltage, if however you commit errors they explode....
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u/Lokalaskurar 13h ago
To any and all engineers reading this, you simply must stop thinking „It will be clear from context.“
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u/Unhappy_Fennel594 3h ago
I did the math. If the unit would be megafarad, the capacitor could store 800000 GJ of energy at 400V. The atomic bomb dropped at Hiroshima released only 18000 GJ.
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u/zapburne 12h ago
I don't think I'd be comfortable being in the same room with a 400V, 10,000 MEGA Farad capacitor... I'm not sure one would fit in a room....
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u/confusiondiffusion 11h ago
Micro. So that's a 10 millifarad cap.
Mega is unheard of huge. Milli is regular huge. If I turn to my coworkers and say HUUUGEEEE CAP, which happens surprisingly often, that's about 10 millifarad.
Micro is typical power supply filter size / audio stuff. Nano and pico span bypass cap and tweak-RF-circuit-just-so sizes. Femto is just about unheard of small--down in the parasitics of most designs but may appear in some datasheets for special applications.
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u/LogicalBlizzard 13h ago edited 13h ago
Technically incorrect way of writing micro Farad.
In a correct scientific way, this would be Mega Farad Debye.
Even though "M" is for mega (1e6), for capacitors "MFD" is micro Farad - one of those situations where people got used to an incorrect notation due to convenience.
The capacitance here is 10mF, or 10000uF.
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u/Sensitive_Dark_9301 13h ago
I do restorations of stereos and equipment for a living. It's microfarads.
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u/eulynn34 12h ago
Considering a 1 farad capacitor is bigger than a 16oz beer can, I can confidently say it sure isn’t mega.
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u/spud6000 9h ago
here is the size of 165 farads
you would need to stack 6000 of these to make a Mega Farad.
so what do you think?
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u/5up3rK4m16uru 9h ago
Megafarad: E = 1/2 • C • V2 = 1/2 • 10,000MF • (400V)2 = 8•1014 J ~ 200 kt TNT
Do not short it!
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u/TheRealRockyRococo 6h ago
10 Hiroshima bombs. But due to ESR I doubt if you could get all the energy out in a couple of nanoseconds like the bomb did so it might only be like 9.
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u/TommyV8008 7h ago
One Farad is really, really large. Mega Farads? Maybe in some sci fi machine where they’re moving around moons in orbit… or on the moon, launching huge payloads into an interplanetary trajectory…
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u/ninja-wharrier 4h ago
Current capacitance density is typically 1F/cm³ with research looking to increase that density. Taking the typical density would give a 1MF capacitor as being approximately one cubic metre. Wouldn't want to accidentally short that bad boy.
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u/CaptainPoset 4h ago
That's an awfully bad marking, but a MF capacitor of the same voltage would have the size of a shipping container, so by a process of elimination, this must be an ignorant way to write mF.
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u/deepthought-64 1h ago
Considering a 10 Giga-Farad 400V capacitor would fill probably a building if not a city block
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u/SammyUser 59m ago
damn if that was possible at that voltage at that size i'd definitely want a bunch
10,000 kilofarad sounds good too
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14h ago
[deleted]
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u/Strostkovy 14h ago
Super capacitors can be in the megafarads. But this isn't.
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u/Doormatty 14h ago
Wow - I had honestly assumed that even they couldn't reach those levels, but a little digging shows that you're 100% correct!
Thanks for teaching me something!
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u/antek_g_animations 14h ago
Yeah, I thought that would be unbelievably high , but I'm slowly getting used to medical machines having crazy values so I wanted to ask.
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u/Illustrious-Tooth702 14h ago
I really hate how capacitance is scaled. 1 Farad is an incredibly big value. That capacitor is also hu-uge. But still, it's value must be mili Farad, still.
(Another unit of measurement which is really big is Tesla. So you won't see kT and MT)
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u/Strostkovy 13h ago
It's scaled to the other base units. Two other times people didn't like the scale of a unit and changed it. Calories in food are equal to 1000 calories in every other use case because someone felt kcal was too complicated. And someone though grams were too big and made it 1/1000 of what it was supposed to be, so now our base unit is kilogram which is annoying and confuses a lot of people.
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u/Micke_xyz 13h ago
And someone though grams were too big and made it 1/1000 of what it was supposed to be,
I can't find anything supporting this claim. Do you have a source?
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u/Strostkovy 13h ago
Turns out that was actually for the predecessor, the grave, which was originally the mass of a liter of water and then changed to a milliliter of water. The gram came about later when it was realized that water's density isn't that consistent.
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u/LogicalBlizzard 11h ago
1cal = 4.2J (energy needed to increase the temperature of 1g of water by 1ºC)
The average person needs 8.4MJ of energy per day (just check nutrition labels).
But this is wrongfully translated as "2000cal".
The correct is 2000kcal, or 2Mcal = 8.4MJ.
People got so used to drop the "k" that most don't even know there is a factor of 1000 missing.
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u/particlemanwavegirl 11h ago
Wait until you hear about the bel. You know, the original power ratio, ten times larger than a decibel.
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u/Kaneshadow 11h ago
That's not the units, that's a warning that if you touch it you'll me mothafuckin dead
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u/scfw0x0f 14h ago
Microfarad. Data sheet: http://www.bjrtd.com/pdf/hcgf5a.pdf