Run Capacitor Fundamentals Class

all right so we're going to talk a little bit about capacitors here [Music] let's go ahead and just put to put the meter on the capacitor scale we will measure what we've got and just see see where we stand so the first thing you always want to do is look at what the rating is so what's the rating of what you got in your hand 20 micro farad 20 microfarads now there's a voltage rating on there too what does it say 370 or 440. okay so a little trick there the reason why it says 370 or 440. so here's why because there used to be 370 or there is 370 volt capacitors out there but that's just the maximum rating that they can handle so 440 is better but if people read 370 on it they'll ask for a 370 volt capacitor to replace it and so a lot of people didn't know that you could replace a 370 with a 440. so amrad and some others started printing 370 or 440 on the capacitors just so that way everybody knew that it was compatible but really when you say 440 you're automatically saying 370 or 440. so 20 microfarads is the rating so go ahead and take the measurement and use the alligator clips which is nice for this purpose it was in a system you'd make sure to discharge it first but we are measuring 20.46 so it's well within its rated operation now you're gonna notice it's a little bit over is that a problem is 0.46 over a problem no what does it say the tolerance is plus ten minus five plus ten or minus five okay so plus ten would be acceptable minus five would be acceptable interesting and so what that's telling you is right out of the box that's acceptable i generally will say plus or minus ten percent before i'm going to measure mention it to a customer and really i'm saying minus 10 because you're almost never going to see plus 10 like we talked about in our previous video so let's go ahead and test the other ones real quick and just see where everyone where all of them stand seven and a half seven and a half all right plus or minus six percent well is it connected on there good 7.6 okay 7.6 all right so that one is also within range of what it should be now this guy here just shows you the inside of a capacitor we got our um basically sheets of mylar or whatever type of plastic that is with metal coatings on both sides and that storage of energy across that plastic between those two metal halves is what makes a capacitor a capacitor which is why when a capacitor starts to get weak what's happening is is that metal coating is breaking off and flaking off it's very thin the reason why modern capacitors fail and the old older ones didn't tend to fail is because they don't have as much foil or as much oil the foil was thicker and the oil was better nowadays the oil isn't as good and the foil isn't as thick that's why they don't last as long as they used to although i do like the amrat capacitors they do pretty well let's take a look at this one here because you can see what it should be you got 10 microfarads between this red terminal and the center and then all around it shows you what the different ratings should be but we've got a problem with this one and what's what's the problem here it's bloated so it looks like a toad that set out in the sun too long after he done got deceased so this capacitor we know is bad we don't even have to test it we're going to what happens is this is a design feature when it overheats pressure builds up and the top is designed to displace like that and it disconnects the terminal so it actually intentionally disconnects so that way it doesn't explode because if you've seen some of these come fully apart they make a giant mess as oil gets all over everything and is not pleasant but we're going to go ahead and test it and see what we get so we'll do the 20 microfarad yep and then the one in the center what do we got we got the dashes of nothingness which means that we have no microfarads we have an open circuit because also this is auto ranging between microfarads and ohms so we have no path whatsoever now some people will teach you on a capacitor to also check from the terminals to ground on the shell that used to be more of a common problem nowadays these are all plastic lined you almost never see a capacitor shorted to ground anymore that used to be a more common problem so really not a test we do but if you wanted to you could take the terminals and measure to ground so let's just show how you would do that real quick this is an example that's it you just check from the different terminals around to make sure that nothing's grounded out and in that case if you measured something from a terminal to the casing that would be a problem right because that would mean that the internal plates or the wires in there somewhere were actually connecting to the metal just curious how long ago did they use those kind of capacitors so the question is how long ago do they use those kind you'll still see capacitors from the 90s 80s that are they're much larger physical size and in some cases they're even going to have a dot which is the side that you need to connect to the common side if it's a single cap so you'll see some of these where you'll have a dot on one side and that's the side that you're supposed to connect to common and the other side is designated to your herm or whatever start winding you're connecting it to modern capacitors don't have that anymore all right so let's talk about what a capacitor actually does what does a run capacitor do not talking about a start capacitor what does it actually do stores and discharges energy stores and discharges energy okay yeah so the blade or the compressor off runs filtering so that the comp you said so the compressor runs smoothly so that the motor whatever motor it's connected to run smoothly okay those are both true statements what do we connect the capacitor to what winding do we connect it to start connected to the start winding right now whatever motor we're using so if it's a blower motor condenser fan motor compressor it's always going to the start winding and if you pay attention to how they're wired you'll notice that one side of the the start winding part goes into one side of the capacitor and then the other side goes to the same side that feeds run so even though it says common it doesn't get connected to the black side of the contactor and usually that's the side that we would call common generally speaking right you have the side that's where you make your measurements on your contactor for your amperage because that's your common for your windings but your common for your capacitor connects to the same side that you connect run but here's what's actually happening inside that capacitor and it's what matthew said you have energy a field that's collecting on both sides and then releasing again collecting and releasing so again for every site so you are seeing one side of this on the other side of this is another metal coating and the one side of all of those wraps connects on the bottom and that's common and then your other wraps connect on top which is the other side of that plate so basically if you imagine in fact they'll call those plates it's as if you have two plates but rather than you just having two plates with some plastic in between that are flat you have two plates with plastic in between that's wrapped over and over and over and over and over again so the two sides don't touch that's the point just like a transformer and a transformer we have our primary and our secondary these two sets of electrons never touch each other it's induced through the iron core the iron laminations here in the same way that on your transformer these two sides don't touch on your capacitor the common connections which connect to one side and each one of these terminals on the outside or if you're looking at it here this side and this side one side connects to the bottom the other side connects to the top and you have two completely different sides to this plate that's wrapped all around the circle that makes sense so the electrons never go from this side to this side a lot of people assume that somehow it's boosting up the voltage it's not when you measure a higher voltage across that capacitor what are you actually measuring have you ever done this where you go across the capacitor when the system system's running and you measure the voltage it's it's higher it's not always it's not always a set thing but it's always higher do you know why it's higher back feeding voltage because the motor is a generator because the motor is acting as a generator exactly so the motor simultaneously as it's spinning that rotor is also inducing additional potential into the stator so while it's acting as a motor it's also acting as a generator that's what we call back emf back electromotive force back emf is showing up in our capacitor and the reason it's showing up is because our capacitor has this separation so that when it generates on the on the start winding side it's actually showing up over here now when it's connecting to alternating current this capacitor is charging and discharging how many times a second 50 to 60 60 times a second in the us 50 in europe right depends on the hertz that's the frequency so it's charging and discharging that fast all the time so it's not storing energy for very long but a capacitor is an energy storage device and in fact if you when you're measuring with your capacitor how do you imagine that when you put this thing in capacitance scale how is it measuring the capacitance of that capacitor yeah jfm yeah how does that work just freaking magic just freaking magic pfm ron kerry used to always say pfm pure freaking magic the question is how does it measure it when you put your meter on the microfarad scale how does it know what the microfarad of this capacitor is well wouldn't it send a slight charge through it to read the difference that microfiber one millionth of a ferret right right and that is a millionth of a volt or something now it's it's the actual what the definition of a ferret i don't remember what it is but it's like a coulomb at one volt or something like that one cool limit one voltage is sensing power so it's in a very small amount it's just looking at because it this this meter knows how much potential it's giving how much voltage it's giving and it's a very low voltage we just measured it right and this meter is less than a volt so it knows how much voltage it's giving it knows how much pressure it's giving and it knows how much current it's taking at that pressure so it can charge and discharge that capacitor and now it sees how much energy now again i'm i'm acting like i've invented a meter and i know exactly how this does this and i don't so i'm not uh let me let me be clear here but that is how it does it right actually send them power function correct so the meter is charging and discharging that capacitor and then it's looking at how much energy that was required to do that that's basically what it's doing now exactly how it's doing it and the math and all that stuff i don't i don't know i just know that is what it's doing it's literally charging this capacitor now why isn't it dangerous now why doesn't it shock me it's such a low voltage because it's a very low voltage so here's the lesson the capacitor is only charged to whatever voltage it's given it cannot boost voltage it's not a voltage booster let's do the experiment take our nine volt battery here put this on volts dc make sure first that we've got nine volts coming out of it yup nine point six volts so we got a good nine volt battery all right now take your jumper leads and wire your nine volt battery up to this 20 microfarad capacitor don't try this at home kids actually it's fine if you try this at home it's not dangerous at all you guys are afraid of a nine volt battery come on give me a break give it a second go ahead and disconnect your leads off the capacitor make sure they don't touch each other when you're doing so all right now measure the voltage on your capacitor i've actually never done this before so i'm really hoping that this works properly not only does it read nine volts it reads exactly what the battery gave it for once that experiment went the way i hoped it would go without prior testing it's actually discharging because the meter even though this is a very low impedance meter it's actually discharging through the meter itself meaning impedance means resistance so this meter has a resistance and it's literally that that power is trickling through if you disconnect it it'll hold its charge it'll stop trickling there's a reason why that same experiment doesn't work as well on alternating current though so if i were to do that exact same experiment and i was to do it with 120 volts i would take that capacitor and wire it up to 120 volts i wouldn't necessarily get exactly 120 volts on the capacitor and i want your theories on why that is because it's alternating okay so what does that mean so it would it would literally depend on the moment that i disconnected that lead where it was at so i could read anything from zero to one across it actually above 120. because 120 is called rms voltage we actually run higher than that so when we measure 120 on a meter your meter is doing a calculation an rms calculation and it's looking at that average you want to do it you can get shark pretty good doing this so let's do it well maybe we'll just shut the camera off before we don't do that test we're absolutely not going to do that test because it's not safe wear your masks at home bye get vaccinated thanks for watching our video if you enjoyed it and got something out of it if you wouldn't mind hitting the thumbs up button to like the video subscribe to the channel and click the notifications bell to be notified when new videos come out hbac school is far more than a youtube channel you can find out more by going to hvacrschool.com which is 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Channel: HVAC School

Views: 504,143

Keywords: hvac, hvac school, run capacitor, capacitor tutorial, capacitors explained, capacitor fundamentals, test run capacitor with multimeter, electrical engineering, electrical engineering basics, hvac training videos, hvac technician, hvac troubleshooting, hvac fundamentals, capacitor, capacitor testing, capacitor testing using multimeter, start capacitor, capacitor types, capacitor start motor, bryan orr, hvac classes, hvac beginners, hvac beginner training, farad, Microfarad

Id: rtxVV2St1T4

Length: 13min 56sec (836 seconds)

Published: Wed Apr 28 2021