Hello for you guys
I have question can you help I want to know whats the deferent between 3 phase & single phase and which one is less consuming in watt and amps I need more information about it .
3-phase consumes less energy however, finding three phase wiring in a residential home is very rare. So be careful what you buy on E-bay.
[Edited by millerman on 11-09-2005 at 09:50 AM]
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Twist any two wires together and you create 230v single phase. Twist all three wires together and add ground for 115v. **NOTE** Before you turn power on stand a very long ways away from equipment because a heavy discharge of secret magic HVAC fairy dust will occur. Too heavy of a discharge can possibly cause some disfunction of equipment requiring highly specialized service personall to come out for mandatory EPA reclamation.
*** NOTE*** Please ignore above information. Patient has been self medicating again.
Think of electricity as someone doing work. Single phase is like one person pounding a railroad spike into the ground, three phase is like having three people each taking a whack at the railroad spike, thus three phase power is a more concentrated form of power. There are different configurations for three phase, so unless you know what you are doing step away from the electrical panel man
Seriously, there are different levels of explanation you could be looking for, depending on whether you've had calculus, or taken a physics class that covered waves.
Taking jdenyer's railroad spikes a little further: one guy pounding the spike is single phase. You could have three guys all pounding the spike together--up!up!up!...WHWHWHAM!...up!up!up!...WHWHWHAM!--and it would still be single phase. (Ok, so it's a spike with a really wide head ... I'm making an analogy here.)
But if one of them suddenly gets the idea that the three of them could all pound at different times, equally spaced apart, well, she just invented three phase. You could think of a picture of a circle with three points equally spaced around it.
The voltage on an AC circuit is a wave, that goes up and down like the sledgehammer (only more smoothly, unless there are lots of PCs and copiers plugged in). Usually in a home you have a bunch of circuits but they're all carrying the same wave, up and down at the same time, like those three guys before trouble came along. (Ok, really in home half the wires are carrying one wave and the other half the exact opposite, up for down and down for up--picture a circle with two dots exactly opposite--and electricians still call that single phase.)
But in a lot of commercial wiring you'll find three conductors carrying waves spaced equally apart.
It's not really a matter of one form of power being more "concentrated" than another, whatever that might mean, but it does turn out three phase is handy for building motors. You can build a motor with three electromagnet coils spaced equally around and the three phase power will naturally make magnetic fields that make the shaft rotate. If you tried to build a motor that way for single phase power, it would just be like trying to pedal a bike by pushing straight down when the pedal is straight up. So single phase motors need various kinds of extra magic to make them go around, and that can cut into their efficiency.
Now, you could go back to the circles and dots, and make the circle have a radius of 120. When you have the two dots exactly opposite, with a ruler you'd obviously measure 120 from either dot to the center, and 240 from one dot to the other, just like the voltages in a typical house. On the circle with three dots equally spaced, you'd still measure 120 from any dot to the center, but now only 208 on a ruler between any two of the dots. Sometimes you might find a house where the two service legs both measure 120 volts to ground but only 208 between them, and wonder how that adds up. Now you know. That house is being fed from two legs of a three-phase transformer. But since you've still only got two of them, you're still out of luck for running three phase equipment.
A cool exception is the GE ECM blower you'll find in a variable speed furnace. The ECM is a pretty ordinary three phase motor with a blob of electronics mounted on the end. The electronics take the single phase power supplied to your furnace and reshape it into three separate waves to drive the three phase motor, a very efficient way to do things. (What's even cooler is how the ECM measures the airflow and adjusts its own speed to arrive at a programmed airflow.)
But if you really want to know what's behind these pictures, and why a ruler between dots on a circle tells you anything about voltage on wires, and how they even have anything to do with each other, and you haven't had calculus, well, now you've got something to look forward to.
If you want to talk 3 phase post in the commercial section......almost non-existant in residential. Bottom line is power company's won't 3 phase homes because cost to consumer is alot cheaper.
If everything was always done "by the book"....the book would never change.