Most homes have a 100A to 200A main breaker. Industrial buildings and farms often have a 300A or 400A main. Factories with lots of electrical machinery have multiple main panels, (often 3 phase), but what is the largest main breaker that is sold?
3000A maybe
We have a 1200A in or plant, but I know they do make a 4000A. I don't know the biggest for sure though.
Geezzzzzz as if that aint enough power!!!! I'd hate to have to pay that electric bill. And imagine the size of that transformer feeding it. The biggest listed on that Westinghouse site was 4000 (for low voltage, meaning 240/120 or three phase 208. I know some buildings have 440 too, I'm not sure just why, I suppose some motors run on 440, or they split it into two 220/240 circuits like they do with 240 to 120.
480 generally comes in as wye 3 phase. They use the resulting 277v line to neutral for lighting They will have transformers to drop that to 208 3 phase, centertapped for the 120.
All of our machines run on 440V 3ph. Keeps the wire size down.
I live it when a visitor says "wow, this is a big place, you must make tons of money". They go into shock when I tell them the electric bill last month was $30,000, the gas bill was $20,000 but goes up when we turn the heat on.
Ed, what is the nature of this place you refer to? Just curious.
Take a look at Alcoa and be thankful for small favors that it's that small... :)
2010 _purchased_ electricity consumption was 55,883,973 MWhr; total corporate direct energy consumption was 278,437,149 MWhr--
I read that Iceland, being a cheap source of energy because of geothermal, was attracting aluminium plants which require massive amounts of electricity...
A nickname for aluminum is "solidified electricity" thanks to the Hall-Heroult Process which takes place in an electric furnace.
Tomsic
For the the power company's high voltage electric lines, it is called a "Recloser". Also when the voltage increases, the amperage decreases, so these are not rated at very high amperages, but are rated for high voltages...
Molded foam plastics. The machines have motors driving hydraulic pumps and run from 5 hp to 15 hp. Air compressors are 75 hp and 150 hp. Miscellaneous blowers, fans, pumps cooling towers, etc.
But a centertap on 208 would only result in 104. Or are the centertaps not exactly centered, and only using the higher voltage half (120 + 88 volts)?
As much wiring as I've done, I have never understood how the 3 phase systems get the desired voltages. Just like how does one get 277v from
480v (half is 240). Then too, why use 277v for lighting? Unlike large motors and electrical heating sources which are more efficient at higher voltages, lighting is one thing that surely does not need higher voltages and would require special bulbs, ballasts, and probably switches too. Seems sort of pointless....
Likely you mean the common point of the "Y" not centertap?
To better understand 3 phase, use a phaser diagram. Draw a circle and from the center outwards draw three lines to the circle's edge each line is 120 degrees apart. Now you have a circle with what kindof looks like a peace symbol. Each line represents a phase of AC power. Now spin the wheel [mentally] at 60 Hz and view from the circle's edge watching the TIP of each line go by. As a function of time, each line will subtend a sinusoidal waveform. Each waveform is what the 3 phase poer is doing.
Now you can strt to play gaimes. What would be the voltage if the three wires were connected between each line tip? What would be the voltage if you measured from the tip to the center? etc etc. You will notice that no matter which connection you make the waveforms will always be 120 degrees apart.
The centertap is 120. It is the centertap of a 3 phase Y transformer.
208/sqr3=120. The center tap of a single phase transformer is half the voltage. 240/2=120. 480/sqr3=277 It is not a center tap of a single phase like 240/120Higher voltage means less amps for the same amount of power. With less amps you can use smaller wire and smaller raceways. Since they use it in most large buildings you can bet it is not pointless.
On 4/5/2012 12:43 AM, snipped-for-privacy@toyotamail.com wrote: ...
As the other posters note, you need to consider the phaser diagram. The Wikipedia article isn't _too_ bad; reading it won't hurt.
But, as to the question posed above, look at it the other way 'round...
Suppose we want to take two phase wires (of a three-phase distribution) and a neutral to make a three-wire household service supplying 120 V between each hot wire and ground. The neutral will become the grounded conductor, the two phases the hot and neutral conductors. If we grant this, the wye voltage is 120, so the delta voltage will be ?3 x 120 =
208 V. This is the three-phase line voltage necessary in this case which is why that is a common distribution value for three phase systems--it was worked out so that the end result will be that desired. Note that the two 120 V sources are not opposite in phase, and will not give 240 V between them.On the other hand, suppose we do want a 240 V service. Then this must be the line voltage, and the voltages to neutral will be 139 V, not 120 V. A 120 V three-phase service will give only 69 V from line to neutral.
Also as noted, the reason for the higher voltages in commercial building is that the lower amperage requirements for smaller conductors translates into a less expensive installation overall. The cost-savings escalate the larger the facility.
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Problem is that the pirate mega banks and brokerages etc give everyone the idea that all businesses are making a fortune or are evil or corrupt.
Similar story...
We rent a local armory for a kid's related sporting event a couple of times a year, always during the winter months. Everyone assumes that the local businessman that bought the armory was rolling in dough. "What a great deal he got! He bought this old building for $1,000 and now rents it out for concerts and events. He must be making boat loads of money."
They change their tune when we tell them that the owner spent 1 million dollars on the roof as soon as he bought it to stop the leaks that prevented any other repairs from being done. Then he upgraded the electric to handle the requirements of the events he planned to hold, installed a fire protection/sprinkler system before the city would let them open, etc. Even with the favorable code treatment the city gave him so that he could start to recoup his money, it's been years and he's still in the hole.
Because we're a non-profit, he rents the armory to us for a few thousand for the weekend, even though it costs him $1,200 a day to heat the place.
BTW...the owner is blind and has never seen the building he owns and operates. Rumor has it that he was told that if had been able to see the building, he never would have bought it. He supposedly wanted to be bring the building back to its former glory days after years of neglect.
I apologize for the "center tap", yes that is the center point of 3 windings in a wye. When they really need 240v instead of 208, it will be a delta service, generally center tapping one winding to get the 120/240v. That will usually be a bigger transformer than the one that provides the "wild leg", "red leg" or whatever they call it in your area. That will be 208v above ground. You will also see this in places where 3 phase is not the main service they want to supply like a small industrial customer in a strip mall. The power company likes it because they can do it with 2 transformers.
If you really want to see something that will make you scratch your head, look at a corner grounded delta. That would be used some place where they have no 120v loads at all. (sewer lift pumps are an example) It is 3 phase delta 240v between phases but you will see 240v to ground on 2 phases and the third phase is grounded (0v to ground). That wire will be white. You will only see 2 pole breakers and it looks like a regular single phase 120/240 until you get out your meter. The breakers also have to have a "delta" rating. (240v line to ground).
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