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Old 15th August 2017, 10:23 AM   #121
psionl0
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Originally Posted by lomiller View Post
They will run 3-phase regardless, it’s just a matter of when/where/how they produce the split phase power that comes into the house. If you don’t have split phase coming into your house, I’d suspect that’s more a case of how your house is wired than what the electrical company has available.
You are clearly conflating how power is supplied in the US and how it is supplied in the rest of the world.

The power poles passing every every residence in Australia all have 4 wires on them - 3 live wires and one neutral wire. The live wires all carry AC at 120 degrees out of phase with each other. If a household is to be supplied with three phase then it needs to tap all 4 wires and have that tapping run to the meter box. It it is to only have single phase power then it only needs two wires running to the meter box - one tapped to the neutral and one tapped to one of the live wires at the power pole.

Originally Posted by lomiller View Post
My understanding is that at least some residential split phase systems are not generated using center tapped transformers, rather they are 2 lines and the neutral from a 4 wire wye 3-phase system. If it’s center tapped, you will have nominal voltages of 120V/240V if it’s directly from a 3-phase distribution system you will have nominal voltages of 120V/210V. 210V is common in commercial settings even if it’s 240V for residential, and most equipment is happy with either
While commercial premises may indeed have 3 phase power supplied directly, I have seen no information that suggests that residential premises are supplied the way that you describe. Until you can provide some links, I will prefer to trust the link that I posted in the OP. (http://science.howstuffworks.com/env...rgy/power7.htm)

Originally Posted by lomiller View Post
WRT current draw, while 240V/210V produces a lower current draw for the same power output it’s typically used specifically because you have a need for higher power draws. As a result, it’s typically going to be wired for higher current draws than 120V.
That's the first bit of theory you have made up that makes sense. Of course, this was pointed out several times on page 1 of this thread.
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Old 15th August 2017, 08:06 PM   #122
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PsionIO is correct for most urban areas in Oz, however it is still quite common in rural areas to have only a single phase (2 wire) system available, or in some areas they actually still use a single wire, earth return system where the poles have only a single wire running along the top!
Center tapping is very very rare, AFAIK it was only some very rural parts of Tasmania and Victoria that had a centertapped 240/480v system and none installed recently (ie after 1970's), certainly I have never seen one in person in NSW or Qld

The center tap 110/240 US system is very definitely the odd man out in the electrical world (along with NTSC mentioned before- I always remember the initals by using the memory aid 'Never The Same Colour') and is really only found in the USA or places they had a strong military presence in for extended periods of time
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Old Yesterday, 07:59 AM   #123
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Originally Posted by psionl0 View Post
You are clearly conflating how power is supplied in the US and how it is supplied in the rest of the world.
No, I’m not. 3-pahse is part of every power distribution system in the world because it’s a more efficient way to deliver power. The only differences are how and where it’s converted into the single phase or split phase power that comes into your house.

Originally Posted by psionl0 View Post
The power poles passing every every residence in Australia all have 4 wires on them - 3 live wires and one neutral wire.
3-phase systems can have either 3 or 4 wires depending on whether they are wye or delta. You can also have a separate ground with either, since neutral isn’t necessarily ground. If the loads on each phase are not balanced there can be current in the neutral in a wye configuration, which is why you may want a separate ground.
Originally Posted by psionl0 View Post
While commercial premises may indeed have 3 phase power supplied directly, I have seen no information that suggests that residential premises are supplied the way that you describe..
Then why are common household products like cloth dryers designed to work with either 208V and 240V?
http://www.google.ca/url?sa=t&rct=j&...HFuYeGD2bEzETw


Originally Posted by psionl0 View Post
Until you can provide some links, I will prefer to trust the link that I posted in the OP. (http://science.howstuffworks.com/env...rgy/power7.htm)
Are you sure you understand what you are linking?
One of the advantages of a 3 phase system is that you can get different single phase voltages by virtue of how you wire it. IOW you can get singe phase 208V or single phase 120V out of a 3-phase system
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Old Yesterday, 08:42 AM   #124
slyjoe
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Originally Posted by lomiller View Post
...snip

Then why are common household products like cloth dryers designed to work with either 208V and 240V?
http://www.google.ca/url?sa=t&rct=j&...HFuYeGD2bEzETw

...snip
Read the specs in your link - single phase.
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Old Yesterday, 08:55 AM   #125
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Originally Posted by slyjoe View Post
Read the specs in your link - single phase.
Lets start again from the beginning. Take a wye 3-phase system, so it has 3 lines and a neutral call them L1, L2, L3 and N.
Connect a load across L1 and N and it will be supplied with 120V single phase.
Connect a load across L1 and L2 and it will be supplied with 208V single phase.
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Old Yesterday, 08:59 AM   #126
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Originally Posted by lomiller View Post
Lets start again from the beginning. Take a wye 3-phase system, so it has 3 lines and a neutral call them L1, L2, L3 and N.
Connect a load across L1 and N and it will be supplied with 120V single phase.
Connect a load across L1 and L2 and it will be supplied with 208V single phase.
I know how wye and delta connections work. I thought you had implied because the clothes dryer could work with 208 or 240 that 3 phase power was supplied to residential homes.

I apologize if i misunderstood your previous post.
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Old Yesterday, 09:04 AM   #127
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Originally Posted by Dabop View Post
Actually most of it goes back to that boomin Edison guy and his DC systems which were + and - 110v DC (one of the limiting factors was increased sparking of the commutator in the dc generators as the voltage increased) Of course DC lost the war of the currents, but not until many Edison DC plants had been installed throughout many American cities. DC had major issues with voltage drop and required powerstations within a mile or so of the end of run- meaning many many powerstations would be required, where the AC system promoted by Westinghouse and Telsla could simply step up the voltage using transformers and step down again near the end user, meaning fewer and larger plants could be built outside the city and lines run in at the higher voltages

Edison 'AC kills' demonstrations were probably the biggest fearfactor about using AC and higher voltages as he went around the country electrocuting animals and even humans (against westinghouses wishes) using Westinghouse AC generators to make the first 'old sparky'- something his own DC generators were incapable of doing due to their voltage limits

By the time many other countries were investing in electric generation, the war of the currents was over and DC had lost, meaning we werent tied to the lower voltages of the Edison systems that many US cities had already invested heavily in- some cities such as New York have only just retired still existing original DC plant (in 2008), but that 110v lower voltage all goes back to those early DC systems
So you can blame Edison for the system you guys are stuck with
Since the primary use of electricity in the early days was lighting, I suspect that one factor in keeping 110v (or 120v) was that it was compatible with the 110v light bulbs. Incandescent bulbs work equally well on AC or DC, but trying to run a 110v bulb on 220-240v will burn it out immediately (unless you put two of them in series).
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Old Yesterday, 09:07 AM   #128
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Originally Posted by lomiller View Post
Lets start again from the beginning. Take a wye 3-phase system, so it has 3 lines and a neutral call them L1, L2, L3 and N.
Connect a load across L1 and N and it will be supplied with 120V single phase.
Connect a load across L1 and L2 and it will be supplied with 208V single phase.
Clothes dryers are used in both residential and commercial settings. I suspect the reason for making them compatible with either 240v or 208v is to allow them to be used for either.

Most commercial power in the US is 440v three phase, but many businesses have a transformer that steps it down to 208/120v three phase.
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Old Yesterday, 09:23 AM   #129
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Originally Posted by CORed View Post
Clothes dryers are used in both residential and commercial settings. I suspect the reason for making them compatible with either 240v or 208v is to allow them to be used for either.

Most commercial power in the US is 440v three phase, but many businesses have a transformer that steps it down to 208/120v three phase.
More like itís an artificial distinction. If you live in a large apparent itís fairly likely your residential power available for an in suit dryer is 208V not 240V. Since only the heating element is actually using they higher voltage youíd never know the difference between center tapped 240V and Delta connected 3-phase unless you took a meter to it.
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Old Yesterday, 10:29 AM   #130
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Originally Posted by lomiller View Post
No, Iím not. 3-pahse is part of every power distribution system in the world because itís a more efficient way to deliver power. The only differences are how and where itís converted into the single phase or split phase power that comes into your house.
Yes you are. "Conversion" to single phase doesn't happen (you just use one of the phases) and "split-phase" power is uniquely North American. So are pole top transformers that supply power directly to the house.

Originally Posted by lomiller View Post
Are you sure you understand what you are linking?
One of the advantages of a 3 phase system is that you can get different single phase voltages by virtue of how you wire it. IOW you can get singe phase 208V or single phase 120V out of a 3-phase system
It is clear that you don't understand what I am linking. For domestic (not industrial) premises, it is clearly possible to feed two of the three phases into transformers and supply a household with two phase electricity that is 120 degrees out of phase.

However, you have not shown that this is the practice anywhere. In fact, many areas may not have 3 phase power running past homes to begin with. The current practice is to feed a single phase voltage into the primary of the power top transformer and run tapped 240 volts from the secondary to the house.

Until you can show that it is otherwise for domestic premises, your theories are worthless.
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Old Yesterday, 12:09 PM   #131
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Originally Posted by psionl0 View Post
Yes you are. "Conversion" to single phase doesn't happen.
If you want to split hairs and just call it connecting a load, thatís fine too, it doesnít make any difference you are still connecting to a 3-phase power distribution system. Conversion is accurate as well because this is part of a wye-delta conversion.
Originally Posted by psionl0 View Post
It is clear that you don't understand what I am linking. For domestic (not industrial) premises, it is clearly possible to feed two of the three phases into transformers and supply a household with two phase electricity that is 120 degrees out of phase.
Itís possible even without the transformers. A transformer is only required if you also want to step down the voltage or produce a center tap.
Originally Posted by psionl0 View Post
However, you have not shown that this is the practice anywhere. In fact, many areas may not have 3 phase power running past homes to begin with. The current practice is to feed a single phase voltage into the primary of the power top transformer and run tapped 240 volts from the secondary to the house.
They all have 3-phase either running past you house or relatively close to it. If you only have a single phase directly in front of your house it is 1 of 3 phases coming off a nearby transformer. Except possibly in rural areas where the distance between houses can be very long, electric companies donít move electricity any significant distance using single phase.
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Old Yesterday, 02:05 PM   #132
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Originally Posted by lomiller View Post
Itís possible even without the transformers. A transformer is only required if you also want to step down the voltage or produce a center tap.
It's a good thing that you are not an electrician. Connecting 7,200 volts directly to your house is the quickest way to the graveyard that I can think of.
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Old Today, 12:38 AM   #133
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Originally Posted by psionl0 View Post
It's a good thing that you are not an electrician. Connecting 7,200 volts directly to your house is the quickest way to the graveyard that I can think of.
I've seen the results after a cyclone where this is exactly what happened, a sheet of corro blown off a roof or fence hit the powerlines, shorting the 11Kv (I think thats what they use in Qld- not my area, I'm down in the 100's of volts lol) to the 240/415 3 phases immediately below

Much sparking, smoking etc ensued, and several houses in that street basically had to replace every single item in the house that was plugged in, some had to basically be rewired, others passed a megameter test, but quite frankly I'd rather a full rewire after something like that, the mains wiring in a house was never designed to handle 10000v plus...
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