Diesel Mercedes
Well-known member
If 3 phase is best phase, and 480v is best volts, why isn't everything run this way? Just curious.
Is it diminishing returns or something?
Is it diminishing returns or something?
Why isn't EVERYTHING 3 phase 480v
- Thread starter Diesel Mercedes
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engineer2
Well-known member
Great for industrial use, but 277 VAC to ground would be rather deadly for home use.
MEngineer
Well-known member
I don't have a good answer myself, but I don't think that is it. Europe has 250v domestic outlets. 250 vs 277 ain't much difference.
I'd think everything electrically operated would have to be much more thickly insulated. That extra size/weight might be prohibitive in use (like power cords and double-insulated power tools). Home electronics, too. 
engineer2
Well-known member
Europe and other countries are 220 to 240 VAC. It is deadly there too.
speed bump
Well-known member
Because it's an extra wire to run for almost no gain if you aren't running motors or pulling lots of power.
Supposedly the 120 v standard in the US is from an Edison Westinghouse feud over AC or DC.
Supposedly the 120 v standard in the US is from an Edison Westinghouse feud over AC or DC.
sparknmike
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If 3 phase is best phase, and 480v is best volts, why isn't everything run this way? Just curious.
Is it diminishing returns or something?
Cost!
As mentioned, everything now needs a third wire. Instead of small devices having switches with one pair of contacts they would have three pairs of contacts. The same goes with circuit breakers. The space required in a breaker panel goes up a lot, and you have an extra bus bar in the breaker panel. Even outlets would need extra contacts that don't exist today, and that would increase the size of the plugs.
For electronics 480V would mean more expensive parts to handle the higher voltage.
A new power grid with 480V three phase also means it would be tough to support the huge range of devices, motors, etc. that exist today that are built to the existing single phase standards.
There may be some other good reasons, but the cost of the parts to handle three phase and 480V is quite significant.
Correct. If everything were a rotary screw compressor it would make sense. Would 3 phase help the resistive heating element in your dryer or water heater? No. Would it make any sense to run your 5W flat screen and sound bar with it?
you don't need a new power grid - 3 phase is in most backyards! and motors could be smaller, more efficient, and cheaper - and you don't need bigger gauge wire because 3 phase spreads the amp draw out smoother.
Anything that needed single phase, well, that's easy.
Anything that needed single phase, well, that's easy.
joeswamp
Well-known member
I heard recently that the reason Europe is on 240V and the US is on 120V was due to the difficulty of inventing an incandescent bulb that ran on 240. The US took the solution of running 120 for most things, and 240 for special large loads (like electric heaters or clothes dryers).
Europe took the solution of running 120V for lights and 240V for everything else. Eventually someone figured out how to make a 240V light and then there was no reason to have 120V circuits in Europe. I've been told that in some old houses you can still find evidence of the old abandoned 120V lighting circuits.
Europe took the solution of running 120V for lights and 240V for everything else. Eventually someone figured out how to make a 240V light and then there was no reason to have 120V circuits in Europe. I've been told that in some old houses you can still find evidence of the old abandoned 120V lighting circuits.
finn
Well-known member
You would, in fact need a new power grid.
Most rural areas and suburban areas have only two wires.
It was a massive program that took decades to electrify the country, but to go three phase would have increased the wire cost by 33%. Remember, it was the depth of the depression when much of the original REA programs were funded.
Most rural areas and suburban areas have only two wires.
It was a massive program that took decades to electrify the country, but to go three phase would have increased the wire cost by 33%. Remember, it was the depth of the depression when much of the original REA programs were funded.
bushmechanic
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Edison was a sadistic *****.
Doesn't surprise me he'd be feuding with someone other than Tesla as well.
Ohmthis
Well-known member
I agree with this for the most part. 3 phase is already in the vicinity of most neighborhoods. Dropping 3 phase for high induction loads would be superior with a simple transformer for 120v needs. We've not needed that kind of power for residential loads though. How many homes have large inductive loads? To me a dryer, electric stove, or air conditioner isn't a large load. We need more 120v loads for small appliances, TV, computer, lighting, and so forth.
North America and Europe have two different systems because we have different needs. We use higher primary voltages because we have farther to run between major drops. Think like this, a town of 150,000 is 100 miles (most wiring runs along roads) from the generation plant. And then the next town of 50,000 people is another 50 miles away. To get good power without a ton of voltage drop the voltage needs to be higher (sometimes 144,000 volts). Much of Europe is densely packed urban areas they didnt need really long primary wire runs. So the voltages are lower and can serve 200,000 people in a few square miles. That is the start of our differences. There are a lot more.
Don't believe for a second that it took someone longer to make a 250v light bulb work. An incandescent is probably one of the most simplest electrical device. A raw wire filament (resister) in an inert atmosphere, with lower added. The first bulbs were DC powered also. Simple ohms law would tell you with a certain voltage, and resistance, what amperage is. So explain why it would be so hard?
Ohmthis
Well-known member
No we wouldn't, I've worked in some of the power stations in and around Louisville. One of them went online in 1914 (I'm pretty sure that before the depression) the generators were 220v 3 phase!!! The grid was built then for, wait for it, 3 phase distribution. But Henry and his 1200 acre farm didn't need 3 phase, why? Because his farm didn't have anything that used it. Had there been a need, there would have been a reason.
Yes it was a huge job to electrify the country, but don't think one extra wire, and it's associated equipmen, would have killed the whole thing.
9C1
Well-known member
If you have ever seen a 480 volt fire you would know why it is a commercial voltage where large amounts of power are needed.
The short story is 240 volts will self extinguish
480 just keeps going until a fuse or CB goes, and that can take a long time.
The short story is 240 volts will self extinguish
480 just keeps going until a fuse or CB goes, and that can take a long time.
Jawn
Well-known member
Would it have something to do with potential arc flash hazard?
OH_Varmntr
Well-known member
Thank you for pointing that out.
3 phase power wouldn't be 33% more expensive because of that pesky 3rd wire, etc...it's already there for the main distribution, and that's what spans most of the long distances between inhabited areas across the country. And if people would pay attention while driving down the roadways in their areas, they would see that 3-phase is largely in use around them already.
But the reasons why we don't have it for general purpose use have already been stated.
joeswamp
Well-known member
It's not just resistance -- the filament also needs to emit light. I believe it's easier to make a bulb for lower voltages because the filament resistance is lower and so the filament doesn't need to be so fine. Edison's original carbonized bamboo filaments worked well at 120V (his distribution voltage of choice) but would burn out quickly at higher voltages.
My understanding is that the metal filament bulbs (ultimately tungsten) were better for higher voltages because you could draw out fine filaments that were tuned for each voltage.
Ohmthis
Well-known member
Joe I agree with you in that the filament has to be at a certain resistance to provide light and be durable enough to last. You are using the bulb as known in its infancy to dictate why power distribution was designed. The tungsten filament was around 20 years before major electrification. If standards were set before the tungsten bulb to 120v, why reinvent the wheel. But my whole point has been that a 120v light bulb did not dictate how and at what voltages we distribute and use our electricity. Do we both agree on that?
finn
Well-known member
So tell me again how three phase 480 volt would work in a house, considering that until the late thirties, at least, houses were wired with cloth covered wire and knob and tube construction.
The first use of electricity in the home was for electric lights, and three phase power offers no advantage for that. The electric washing machine was probably next, or possibly the radio.
Your home, if it had any central climate control at all, had a steam boiler or gravity warm air system, neither of which required three phase power
Electric power tools hadn’t been invented: you used a hand saw and brace and bit.
The only place three phase offered any advantage was in large factories. The added expense of adding three phase capability for homes was wasted money.
The first use of electricity in the home was for electric lights, and three phase power offers no advantage for that. The electric washing machine was probably next, or possibly the radio.
Your home, if it had any central climate control at all, had a steam boiler or gravity warm air system, neither of which required three phase power
Electric power tools hadn’t been invented: you used a hand saw and brace and bit.
The only place three phase offered any advantage was in large factories. The added expense of adding three phase capability for homes was wasted money.
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ddawg16
Well-known member
Wow....some of the responses are funny.....
Actually, both the US and Europe have the same voltage.
We all have 240 going to our houses.....the US just happens to use the neutral so we can get 120 Vac.
Anyone get bit by 240? Not fun. Try 480. Better yet, don't. You most likely won't be able to tell us how it felt.
In reality, everyone has 3 phase available at the pole....the transformers for your house only use two of the phases.
When you get down to the small motors found in the typical house, there is no cost/performance advantage to running them off 480. Compounding that, keeping all of your motors phased properly would be a real *****. You buy a new vacuum? 50/50 chance the motor will turn the way you want it to. Anyone who has done commercial work with 480 3-phase motors knows what its like to 'bump the motors' to check for rotation.
The comments about the light bulb above? Good lord...**** is getting deep.
Surprised no one asked by we have 60 Hz and everyone else 50 Hz.
Actually, both the US and Europe have the same voltage.
We all have 240 going to our houses.....the US just happens to use the neutral so we can get 120 Vac.
Anyone get bit by 240? Not fun. Try 480. Better yet, don't. You most likely won't be able to tell us how it felt.
In reality, everyone has 3 phase available at the pole....the transformers for your house only use two of the phases.
When you get down to the small motors found in the typical house, there is no cost/performance advantage to running them off 480. Compounding that, keeping all of your motors phased properly would be a real *****. You buy a new vacuum? 50/50 chance the motor will turn the way you want it to. Anyone who has done commercial work with 480 3-phase motors knows what its like to 'bump the motors' to check for rotation.
The comments about the light bulb above? Good lord...**** is getting deep.
Surprised no one asked by we have 60 Hz and everyone else 50 Hz.
Ohmthis
Well-known member
Surprised no one asked by we have 60 Hz and everyone else 50 Hz.
It's because 60 is more than 50 and more is better.........Right???????
It's because 60 is more than 50 and more is better.........Right???????
In europe the voltage between the phases and neutral is 230V these days.
It is my understanding, that the main goal of 3 phase, is to aid in the starting of large electric motors, something we see less anymore, with the reduction of heavy Manufacturing, at least around here.
I live in the country but have three-phase coming by my house and that goes to an empty old commercial building a few houses down.
As far as the voltage, it's amperage that kills and since it only takes one amp to electrocute so it seems to be rather moot point.
120 240v seems to get the job done so maybe that's why they go with it.
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I live in the country but have three-phase coming by my house and that goes to an empty old commercial building a few houses down.
As far as the voltage, it's amperage that kills and since it only takes one amp to electrocute so it seems to be rather moot point.
120 240v seems to get the job done so maybe that's why they go with it.
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OP
Diesel Mercedes
Well-known member
Learned a lot today, thanks for the discussion guys.
Mechanical Noise
Well-known member
If making a 240V carbon filament light was a problem, a manufacturer could simply put two carbon filaments in series in the same bulb. Carbon filament bulbs with two parallel 120V filaments were made in the early days of the light bulb and putting the filaments in series would be trivially easy.
My first thought on this is that in the early days of electrification, the US was likely the cheapest source for light bulbs and they wired up for US light bulbs until the European manufacturers caught up.
dr_clyde
Well-known member
This is a very interesting discussion. I am not an electrician, so take that for what its worth, but I find this kind of stuff very interesting.
The straight answer is, because its not necessary for residential use.
In the good ol USA, we have at least 5 types of electric service.
The most common is whats called single phase 3 wire, split phase. This is what you have at your house. ONE PHASE, 3 wires. 2 hots and a neutral. Any one hot to neutral is 120V and hot to hot is 240V. The neutral wire is center tapped on the pole transformer giving you half the voltage of the hot line. As the name implies, you are taking one phase, and splitting it to make 120V. Contrary to what some people say this is NOT 2 phase power. You are still only using ONE phase. 2 phase is incredibly rare, but does exist in Connecticut and Pennsylvania.
The two most common 3 phase systems are 3 phase, 4 wire wye and 3 phase 3 wire delta.
3 phase, 4 wire wye is most common in commercial settings. Usually called 208 3 phase, it is mostly used in places like office buildings, schools, hospitals, and places like that. Used to power things like large HVAC and medium motor loads like pumps and small machinery. I have this in my shop. It is popular because at 208V it is pretty safe, and depending on the line and transformer configuration, you can pull a 277/480V single phase in to power large light banks. Lots of commercial lighting is 277V like in schools or wal-mart. It also has a neutral wire, so you an easily get 120V service without a secondary transformer. It behaves much like a blend between split phase and 3 wire delta service. Using transformers, you can get pretty much whatever voltage you want with this service, within reason.
Then there is industrial 3 phase, 3 wire delta. This is typically supplied at 480V, and is geared toward large motor loads, and places that need 600V plus. Because there is no neutral, you can't pull 120V off this service without a secondary transformer. This is often called true 3 phase, due to the lack of a neutral and 3 equal phases.
The weird one that you find in rural areas is called 3 phase, 4 wire delta. Sometimes called "wild leg" 3 phase. Works kind of like a blend between regular delta and split phase, this delta has a neutral. It has 240V between the phases. Two of the phases have 120V between them and the neutral, but one has 208V, the wild leg. Very handy if you have a demand for some lighter motor loads, need 120V and can only have 1 service with no external transformers. Think farmers and other isolated places.
The straight answer is, because its not necessary for residential use.
In the good ol USA, we have at least 5 types of electric service.
The most common is whats called single phase 3 wire, split phase. This is what you have at your house. ONE PHASE, 3 wires. 2 hots and a neutral. Any one hot to neutral is 120V and hot to hot is 240V. The neutral wire is center tapped on the pole transformer giving you half the voltage of the hot line. As the name implies, you are taking one phase, and splitting it to make 120V. Contrary to what some people say this is NOT 2 phase power. You are still only using ONE phase. 2 phase is incredibly rare, but does exist in Connecticut and Pennsylvania.
The two most common 3 phase systems are 3 phase, 4 wire wye and 3 phase 3 wire delta.
3 phase, 4 wire wye is most common in commercial settings. Usually called 208 3 phase, it is mostly used in places like office buildings, schools, hospitals, and places like that. Used to power things like large HVAC and medium motor loads like pumps and small machinery. I have this in my shop. It is popular because at 208V it is pretty safe, and depending on the line and transformer configuration, you can pull a 277/480V single phase in to power large light banks. Lots of commercial lighting is 277V like in schools or wal-mart. It also has a neutral wire, so you an easily get 120V service without a secondary transformer. It behaves much like a blend between split phase and 3 wire delta service. Using transformers, you can get pretty much whatever voltage you want with this service, within reason.
Then there is industrial 3 phase, 3 wire delta. This is typically supplied at 480V, and is geared toward large motor loads, and places that need 600V plus. Because there is no neutral, you can't pull 120V off this service without a secondary transformer. This is often called true 3 phase, due to the lack of a neutral and 3 equal phases.
The weird one that you find in rural areas is called 3 phase, 4 wire delta. Sometimes called "wild leg" 3 phase. Works kind of like a blend between regular delta and split phase, this delta has a neutral. It has 240V between the phases. Two of the phases have 120V between them and the neutral, but one has 208V, the wild leg. Very handy if you have a demand for some lighter motor loads, need 120V and can only have 1 service with no external transformers. Think farmers and other isolated places.
Mechanical Noise
Well-known member
My understanding is Edison wanted a 100V minimum voltage. So he ran his generators at 120 volts. Customers close to the generator got a steady-ish 120 volts DC. So the 120V "standard" is actually quite old. Problem was, voltage deteriorated from the generated voltage to the minimum voltage with distance and load. Customers on the edge of the service area got 100-120V, depending on the overall load on that branch.
I believe Edison was making bulbs in 5V increments, from 100V to 120V during this time.
With AC power, it's like most of the customers are living right near the generator.
The war of the currents ended when the people who formed GE got tired of that silliness and tossed Edison out on his ***.
Sal Bandini
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You do not have 2 phases coming into the house. It is single phase 240, which is center-tapped.
Line to ground voltage is 120V while EU line to ground voltage is 230V.
twistlock outlets solve that problem - maybe we'd finally get home builders to pay attention to color codes and stop installing GFCIs with the hot/neutral swapped? lol
a man can dream
redmondjp
Well-known member
Why do residences have single-phase instead of 3-phase power? Because of Edison. His DC service, known as an "Edison Service" was a +120VDC line, a -120VDC line, and a neutral. So you had two hot legs, each having 120VDC to ground, and 240VDC between them.
When Tesla/Westinghouse's AC systems took over, these Edison electrical services were retrofitted to AC, with the neutral center-tapped on a 240VAC secondary winding, providing two hot legs with 120VAC to ground, and 240VAC between them. This was done so that the very same light bulbs would continue to work with the new AC service. Universal (brushed) motors used in small appliances that worked on DC, also worked on the new AC power.
So that's the real reason.
When Tesla/Westinghouse's AC systems took over, these Edison electrical services were retrofitted to AC, with the neutral center-tapped on a 240VAC secondary winding, providing two hot legs with 120VAC to ground, and 240VAC between them. This was done so that the very same light bulbs would continue to work with the new AC service. Universal (brushed) motors used in small appliances that worked on DC, also worked on the new AC power.
So that's the real reason.
joeswamp
Well-known member
This might be true. I have to say I have no idea why you couldn't just put two filaments in series, seems to me like it would work. It could be that doubling the filament length made the light bulb too expensive, or maybe they couldn't support such a long filament (or if they did so it cooled the filament too much). I do know that light bulbs are one of those "devil in the details" devices. For example, coiling the filament was a huge deal because it somehow changed heat transfer effects and allowed the filament to run hotter, giving significantly more light.
My brother told me about the challenge of high voltage bulbs based on a book he read about the history of electrification. I'll see him over the holidays and ask him about it.
In the meantime, here's a description of why 120V was chosen in the USA and it describes light bulb voltage being a factor:
http://www.answers.com/Q/Why_was_12...of_homes_in_the_US_and_not_some_other_voltage
ttpete
Well-known member
The reason Edison developed 3-wire DC service was to save on copper. When both legs are drawing equal current, there's no current flowing in the neutral conductor, so it can be smaller. Edison generated 110 volts at the powerhouse at high amperage and that required very large conductors to eliminate voltage loss over long distances. By distributing at 220 volts, the amperage needed was halved saving the cost of copper. Edison used 2 110 volt DC generators wired in series with the neutral taken from the connection between the generators.
Alchymist
Well-known member
Not true in rural Pennsylvania. Many places where only single phase is available. In fact, the 3 phase line ends near our house - three wire primary feed comes past the house from the south, and a little way down the road it goes to two wire primary which continues on up the road.
Ji m
Well-known member
Most residential in the USA is 115/230 Delta
Delta uses triangle shaped windings,
with the neutral indexed between two phases of the 'delta'.
The third phase, farthest from the Neutral becomes a high voltage "*******" leg to ground/N and is seldom used.
So you end up with 115/230 single phase in houses.
Most commercial 3 phase is Y 120/208v or 277/480,
Y shaped windings where the neutral is center tapped (center of the 'Y') so voltage to N remains the same for all 3 legs, and there is no higher voltage phase to Ground/Neutral.
As far as the difference between a 120v shock and a 277v shock,
I have no idea how many times I've been hit with 120,
but I can tell you exactly how many times I've gotten 277 (twice), and in great detail
277 kills more than any other voltage,
now that lights draw so little power (LEDs),
I'd like to see things go the other way and switch to 120v for commercial lighting.
Delta uses triangle shaped windings,
with the neutral indexed between two phases of the 'delta'.
The third phase, farthest from the Neutral becomes a high voltage "*******" leg to ground/N and is seldom used.
So you end up with 115/230 single phase in houses.
Most commercial 3 phase is Y 120/208v or 277/480,
Y shaped windings where the neutral is center tapped (center of the 'Y') so voltage to N remains the same for all 3 legs, and there is no higher voltage phase to Ground/Neutral.
As far as the difference between a 120v shock and a 277v shock,
I have no idea how many times I've been hit with 120,
but I can tell you exactly how many times I've gotten 277 (twice), and in great detail
277 kills more than any other voltage,
now that lights draw so little power (LEDs),
I'd like to see things go the other way and switch to 120v for commercial lighting.
sberry
Banned
277 to ground, ouch, what is the Europe to ground? Here 240 is still only 120.
ttpete
Well-known member
The older office buildings I worked in had 277 volt fluorescent lighting.
r_olson_06
Well-known member
They run a 230v/400v system mostly. Certain parts of France I have heard run a 440v. The do not use the Earth as a conductor.
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r_olson_06
Well-known member
If I recall around here. 3 phase is not allowed in single family dwellings. 480v is great if you are running 3 phase loads mostly motors. 480 is usually has a phase voltage of 277 ground as others have stated. 277v is dangerous because if the phase comes in contact with a ground it can maintain the arc poses a fire risk. If a breaker doesn't have a high enough interrupter rating it will not be able to open the circuit and break the arc.If 3 phase is best phase, and 480v is best volts, why isn't everything run this way? Just curious.
Is it diminishing returns or something?
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apollo11
Banned
480v toasters would be awesome