Why Transformers Use kVA Not kW
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Date: 2023-11-17
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Comments and reviews: 28
Daniel
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
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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
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dos
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.
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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.
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MAYONESERO
Ive 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 Joules losses. Reactive power plays a crucial role to sustain voltage across the grid. I know its a short video and it cant 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!
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Ive 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 Joules losses. Reactive power plays a crucial role to sustain voltage across the grid. I know its a short video and it cant 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!
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Leander
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.
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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.
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OceanBagel
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?
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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?
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Dilley
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
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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
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Stranger
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.
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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.
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TempusFrangit
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.
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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.
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Infrared73
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. :)
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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. :)
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Tony
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.
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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.
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Kanav
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
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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
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Shi
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.
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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.
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Andrew
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.
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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.
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Wnglok
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.
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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.
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David
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.
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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.
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Alejandro
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.
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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.
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ryan
VARs arent useless theyre very necessary. You always see the beer analogy but no one actually ever explains what they are. I work at a Power Plant and we deal with them daily both receiving and sending them to the grid
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VARs arent useless theyre very necessary. You always see the beer analogy but no one actually ever explains what they are. I work at a Power Plant and we deal with them daily both receiving and sending them to the grid
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rjrich
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.
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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.
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Ted
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.
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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.
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AB
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.
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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.
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Just
One problem with your video. Your illustration shows a generator feeding the transformer. It should bevan alternator generators make DC, alternators make AC. Transformers only pass AC.
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One problem with your video. Your illustration shows a generator feeding the transformer. It should bevan alternator generators make DC, alternators make AC. Transformers only pass AC.
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Applasamy
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.
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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.
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John
Would engineering mindset make a video about running generators in parallel? And also adding and talking off load of generator sets? Thanks.
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Would engineering mindset make a video about running generators in parallel? And also adding and talking off load of generator sets? Thanks.
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Snowy
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
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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
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ray
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.
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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.
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NICk
Thanks
My teacher The Engineering Mindset
PRODIGY The Engineering Mindset
From Nick Ayivor from London England UK
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Thanks
My teacher The Engineering Mindset
PRODIGY The Engineering Mindset
From Nick Ayivor from London England UK
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The
Using beer to illustrate Electrical Engineering principles? If it wasn't for the accent I'd swear you were American.
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Using beer to illustrate Electrical Engineering principles? If it wasn't for the accent I'd swear you were American.
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Leggo
we were taught in college that apparent power isnt consumed as heat. heat only comes from real power.
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we were taught in college that apparent power isnt consumed as heat. heat only comes from real power.
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