Why Transformers Use kVA Not kW
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- Опубліковано 28 тра 2024
- Why do transformers use kVA and not kW, find out why here. Why transformer rating in kVA why transformer not rated in kW.
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Reactive power is the energy which capacitors and inductors consume to create electric/magnetic field... but these passive electrical elements only store the power not change it to heat and this energy just flows from source to the load and backwards, which contributes to the total transmitted current thus higher power loses on electrical power lines.
Correct ... I tried to explain this in one of his previous videos, but no feedback ... and obviously nothing was learned. Reactive power is NOT a direct loss, it osciallates back and forth
...and a major design factor in antenna design and other AC or RF applications. But you leave the question open here. Where does the oscillating power ultimately go? Are you suggesting that it is ultimately consumed to do useful work by the motor? Does it oscillate infinitely? Dissolve into a parallel universe?
@@TheCablebill yes, it osciallates infinitely in theory ... if you keep the source connected to a non-ohmic load .... so it keeps on oscillating and taking up the capacity and creating some additional heat losses
I was going to say, I think his definition of reactive power (kvar) is wrong. Glad to see someone else caught it. It's the power that is stored into magnetic fields via inductors, and electric fields via capacitors. It causes more current to flow in the system, but that energy is NOT wasted, it is stored. When you pass current through an inductor, you create a magnetic field, this energy is not wasted, it can still do work, but it's simply stored as a magnetic field. Similarly, when you pass current through a capacitor, you create an electric field, and again this energy can do work, it is not wasted, it is stored energy. So you will see current flowing, but no work is done, all the energy (reactive pwr) is being stored.
Written like a true Englishman. Beer needs a little bit of foam. ;)
Right? Without the protective foam layer, your beer’s volatiles will oxidize and leave the drink tasting stale after a short period of time. Gotta have at least a couple fingers of foam on the head so the beer beneath can taste fresh at least most of the way to the bottom. Either that or, I guess, you have to drink your beer out of a smaller glass, lmao
@The Engineering Mindset reactive power is not useless, contrary to what we've been told. It helps with voltage control locally at the generator. A capacitor injecting VARs can boost low-voltage. You find them a lot in rural areas. It is the primary contributor to magnet fields which induction motors need to operate, as well as transformers.
Not to mention how disappointing is a glass of beer without foam...
Produced by someone who never went to a pub in Germany. There is an art to serve a Pilsener. Foam isn't bad. What Americans do wrong is to serve it semi frozen rather than chilled. Last time I had one in a bar in the US the foam froze over. Next one I.ordered I asked him to take a fresh Glas and instead of taking it out of the freezer I asked him to rinse it in warm water first
KVA is potential. KW is the usage.
Nice analogy, much like the water pipe for IVR. Thanks for taking the time to present your material in a way that's understandable to the laity but is still technical enough for those that have touched the industry to not get bored.
All I keep thinking about with the Beer analogy is that some countries or regions want foam on their beer. I've even seen glasses in the Netherlands where they have a line where the liquid should be at with the rest being foam.
I still understand the analogy, but it definitely makes me wonder about the local beer culture surrounding him. :)
Sir, we dutch people do not need a line to show where the liquid should be at.
We use our fingers.
2 fingers should be foam, the rest should be beer.
And if there aint enough foam on it, the beer is considered DEAD.
As in, Not Alive.
As in: Mort.
As in: Undrinkable.
Rubbish.
Pls consider the FACT that we dutch invented Heineken. (or well, mr Heineken invented it.)
I do not say that that is the best beer, but it is known all around the world (thanks to the fact that mr Heineken senior went to New York shortly after Prohibition was ended, thereby securing his position on the market with his beer).
Anyways: A good beer should have at least 2 fingers of foam ontop.
It is just a must, no buts about it.
Nope, sorry, i cant accept any arguments trying to convince me otherwise, because there are none.
ps, 2 fingers wide, not long, obviously
PPS: (and sorry if this makes me a troll, but who cares)
Heineken is not the best beer, btw. And the other beers produced in the Netherlands and Belgium (the dutch speaking half of the country, which basically is the Netherlands but they are just to ignorant to understand it but that is another discussion) who are of much better quality (some at least) also require a nice foam topping.
They are rubbish when they lack a nice foam cover.
It’s the same with electricity, in most homes and businesses you only pay for the beer. The foam is free and costs the generator.
But factories and heavy industries that use loads of electricity have a different sort of meter and have to pay for all they use and therefore try to minimise the wasted ‘foam’
@@bertjesklotepino Totally agree. In Poland it is the same, although not all barmen keep it that way. Foam is a must. Many Bavarians will refuse the beer if there is no foam with 2 widths of a finger. I saw it myself. They were quite unhappy about it 😅
If active power ( true power) and Apparent power were EQUAL, then the power factor would be 1. Therefore the transformer would be listed in Kw.
An all resistance LOAD would account for this (Kw) ratting.
Reactive Power is not lost in the form of heat, it is transformed into electric energy (for capacitors) or magnetic energy (for inductors) temporarily and will be released back. Heat on the other hand, is true power, but it is not used by you, so it is wasted true power.
It most definitely can be lost as heat. A highly loaded transmission line has a lot of inductive reactance and that is lost as heat and is known as line loss. The more load on a transmission line, the higher the line losses due to the inductive reactance. There is also some loses due to the actual resistance, but with AC you have the added inductive losses that only increases with current flow. Which is one reason why HVDC lines can transmit more power over the same size conductor than and AC line. There is no inductive loses in a DC line. There are other loses in the converting from AC to DC and back, but for a long time now, those loses are less than the losses for an equivalent AC line.
This video explains the difference between apparent power and true power very well, but it doesn't explain why the convention is to use kVA for apparent power. 1 watt is equal to 1 volt-amp by definition and apparent power could be expressed in kW just the same without any loss of accuracy. So there's extra meaning given to the unit label beyond the literal definition. But... why is that the convention, and why not label it as something like kWa for kilowatt apparent power, kWt for kilowatt true power?
@@Peter_Enis I understand that, but it doesn't explain why the convention is to indicate that by putting the units in a different equivalent form.
If you are the director of an energy-company, you wanna know how much a transformer can handle; voltage and ampere's and how efficiënt it is (and cost..)
Knowing that it can handle 10000kwh doesnt say at what voltage......could be 5000V, could be 10.000V etc etc..... now how can he choose his transformer?
It will deliver the rated amps @ rated Kv. The end user determens the power factor. The watts if you will
@@Peter_Enis You're still just going on about the difference between real and apparent power, which isn't the question. The question boils down to this: why is this information encoded into the unit label instead of being given a name? Like I said before, volt-amps and watts are equivalent units that are given extra connotation beyond their literal definition in this specific application. But why is that the case?
@@Peter_Enis First it would be 10000kw not 10000kwh. But even then knowing that it could be 10000kVA doesn't tell you the voltage or current either
Thank you for sharing your knowledge
I agree with the distinction of between apparent power and true power, but I don't agree saying reactive power is loss through heat.
For me, it's like having 2 mass objects and a spring between them. if you want to move mass 2, you have to push mass 1 and compress the spring. When you push mass no1 you only compress the spring and mass 2 is stationary, once it's compressed, mass 2 starts moving. The useful power to move mass 2 is much lower than what you have input in mass 1. That difference can not be used to move mass 2 because is compressing the spring. But that energy is not lost, it is stored in the spring as elastic deformation. When you release mass 1, that "useless" energy will be used to decompress the spring and move the 2 mass objects apart
Some energy is lost as heat in all transmission lines. Reactance sends energy from the load device back toward the power source in a wave out of phase. So what happens to this energy on the return trip?
@@TheCablebill the point is even if you had a perfect world where no loss through joule effect, you would still have reactive power. In the example I gave, if there was friction, some energy input into the system would obviously be wasted as heat, but still most of it is stored in the spring. And that is what reactive power measures
The power Factor is NOT equal to Efficiency. It may affect the efficiency but it is not efficiency. Losses in a motor or generator are governed by current (I square R losses including eddy currents) and frictional losses (the friction created by the fluid the parts are in, e.g. air, hydrogen, water, etc., and by bearing friction). For a fixed voltage and KVA the power factor determines the current affecting the current losses but the efficiency is also impacted by the frictional losses in the generator or motor. To summarize, efficiency is a function of the power factor (as it affects current) but is not equivalent to efficiency. Usually is an almost parabolic curve for a fixed voltage, temperature, and speed due to I2R losses since fluid losses at a given speed are relatively constant depending largely on viscosity which is largely temperature dependent for liquids and pressure and temperature dependent for gases.
😢😅😅😢😮😢😢😮🎉❤😅😢🎉😂😮🎉😅❤❤😂😅😢😅😢
He isn’t saying it is equal to efficiency, but that it is basically like efficiency. We want to minimize reactive losses to increase the power factor, just like we want to minimize losses in a motor to increase its efficiency.
Good explanation, bit like when you give someone directions there is always a pub in there as a reference to turn left or right at 😂
Great video Thank you
Well , we do have to use impedance to complete the calculations and design. Transformers are mainly AC. When I select a transformer I need kVA.
Some residential customers are just charged for active power, not reactive power. However, the "lost" reactive power cost should be included (explicitly or implicitly) in a utility's pricing model and spread over all customers; somebody has to pay for that.
Regardless, I read the average residence does not have a lot of reactive power. Big Clive stated the utilities may start charging for that reactive power in the future.
On the other hand, industrial customers may be charged for low power factors (reactive power).
Billing schemes vary so much so these are just examples. Some industrial customers negotiate bespoke pricing arrangements.
Would engineering mindset make a video about running generators in parallel? And also adding and talking off load of generator sets? Thanks.
The generators require synchronizing in lock step.
When removing a generator that is in service from the system, you need to back down the load with no current flow before opening the breaker to prevent a sudden loss of power by upsetting and embalancing the system.
I do like that explanation.
I'm wondering about the efficiency analogy, one could think the efficiency of the motor is part of that. But as evidenced by the light bulb, which has a pf of 1 but only turns like 1% of energy into light, this is not the overall efficiency. Rather, it's whether the maximum current is drawn when there's maximum voltage. Because drawing 20A of current and creating a lot of heat in the wires is okay when there's 200V and you're getting a ton of power (20x200=4000W) but it's useless if there's only 5V available. So pf determines the phase shift between the sine waves of college and current.
I like the foam on the beer 🙃
Yes...bartenders and restaurant owners here in NJ charge you for a 16 oz pint of beer, but you usually end up with 12 oz of beer in that pint glass because there is 1/2" of foam on the top. One of the reasons why I don't bother getting beer while I'm out anymore!
More than meets the eye
excellent analogy!
Thanks 👍
My teacher The Engineering Mindset
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AC power transformers use kVA ratings so you can size conductors correctly per the NEC.
The best way i was taught to understand power factor correction, was to imagine moving a chicken egg 1 inch. You would not use a bulldozer, but your little finger instead. The object being to show using the least amount of energy to achieve the objective.
that feels more like impedance matching
Beer should be the default measure of any unit of mesaurement.
I propose the designation: KW (not kW) to indicate Kegowatts.
Power factor is not efficiency. Efficiency is defined in a two-port device as output active power divided by input active power. Power factor is defined in a one-port device as the active power divided by the apparent power.
The reactive Power cannot be eliminated in devices that works on Electromagnetism but yes we can use high permeability, low Reluctance materials to meet our Tesla requirements using lower value of current which will be used to drive the device
Flux(Tesla) = permeability * Number of turns * Core Area * Current
I’ve followed you for a long time and respect your work, but this is wrong and misleading. Reactive power is not a power loss, I see what you mean but it feels you are tying it to Joule’s losses. Reactive power plays a crucial role to sustain voltage across the grid. I know it’s a short video and it can’t cover the whole topic as it is complex. I would have tried to explain that true power is not the only one consumed, it depends on the nature of the load, that is why transformers work in kVA. Although that would be an oversimplification it would not be false nor misleading. Keep up the great work!
I love how you used beer for analyze. Most people can relate to that. Great presentation!!
But unfortunately it is wrong, the foam converts to beer over time.
Instant comprehension due to analogy
I needed to drink the beer before it was clear.
"Beer is your true power"
Yeah pretty much
Amazing explanation of 3 types of power 💯🔥
👍👍
NOW i get it..... thirsty too
: I knew the answer beforehand but now after watching this video I don't know the answer anymore :D
I love when people use beer to explain things to me
we were taught in college that apparent power isnt consumed as heat. heat only comes from real power.
They should stop using the beer glass analogy to describe their reasoning. Many great electricians turned to alcoholism to understand this concept. 😂
We do want the foam
Actually, the Autobots might use kVA, but the Decepticons use Hydroweasel Power.
That hurt
Efficiency instead of "maximum possible power output", people will just messed up, the reactive power isn't lost! It's exchanged with the source, some additional current is flowing so a little bit more energy is lost by joule effect but the power factor is absolutely not the efficiency! A 1% power factor device can get a 99% power efficiency.
You said what people think reactive power is 🥲
*IN OTHER WORDS,* "VA" is only used before people assume that W is about active load. Without this assumption, it would have been totally fine to use W for transformers, since W can be total, active or reactive, depending on the case. For example, Wt would be total, Wa active, Wr reactive. However, people are not used to this, so we have a different scheme with "VA" for Wt.
Thanks for this.
If i did not think i was stupid before i read this, i now am absolutely sure that i am stupid.
So thanks for pointing this out to me.
Let's skip the next video and just have a beer with no head. Kinda like skipping school but with no going to talk to the principal. 😂🤣😂🤔
I love the beer example! 😂👍🏼
Is this why transformers… Wine?
I get a buzz from them.
I strongly disagree on how you think a beer has to be served. Thanks god you did not say that it is supposed to be warm too 😂😂😂
Hmmmmmm Beeeeerrrrr!
Who invented the transform - Takara Hasbro 😅
VA is watts.
1:02 Bavarians would not agree with that statement 😉😂
mmmm beer
I’ve never really understood power factor.
Power factor tells you how much energy is lost in a piece of equipment while it performs its task. In the video an example is given of a 60Kw motor. 60Kw measures how much work it does. It takes 67.4kVA input to get that much work out. Dividing the output (60Kw) by the input (67.4kVA) gives us the power factor of 0.89.
I heard that you guys overseas are weird xD, but normally if your bartender gives you full glass of beer and little foam he should not be a bartender and he just ruined your beer. Cheers from Czechia.
So long as the foam doesn't touch my nose, it's OK.
WE DON'T WANT FOAM ON BEER? PEASANT! *angry german noises*
Reactive power.
Because we don't have naturally occurring energon here on earth, they had to use SOMETHING.........
I think BEER ANALOGY is not accurate at all,when it comes to REAL and APPARENT POWER.Why not just simply use a GLASS having 80% water?Beer foam still have some contents in it.While air have no usable water.
Air does have water in it. (RH)
Beer is a more fun analogy is the simple answer. Also, the water analogy doesn’t work as well as the beer analogy since the reactive power is still used power. It’s not that it doesn’t exist or that it isn’t made of power (water), it’s that it IS power, but that power is wasted. If we assume beer foam is unnecessary or a waste of space in our glass then that is perfect for the analogy whereas the empty space in the water cup implies that the problem is to do with not enough power as opposed to wasted power. There is *one* problem with the beer analogy though: beer foam serves an important purpose in a good beer whereas reactive power is generally of no benefit.
This video is just not correct. It's more like you don't want your 30KVA power generator only give to 15KW enengy and you may need to spend more on correcting the power factor. If not you're going to need a 50KVA generator for 25KW power demand.
Using beer to illustrate Electrical Engineering principles? If it wasn't for the accent I'd swear you were American.
Transformer is not a load.
Well, it is a little, there are inherent losses in them, but if designed well, those losses are minimal.
Because they are over loaded.
Please send subtitles in Russian!
first
Noone cares