how do we get 120, 240, 480 volts?

Answer 1

If the voltage source is very high, then a step-down transformer may be used.
If the voltage source is low, then a step-up transformer may be used.
If the supply voltage is to low, a two or three phase system may be used.

Answer 2

I love pretend electrical experts.
The high voltage wire outside your house is usually 7200 or 12500 volts. The electric company puts in a transformer to give you what you want. Your house will have three wires coming in. 2 hots and a neutral. The neutral and either of the hot wires will give you 120v. The hot wires arre opposite polarites (they switch polarities 60 times a second, but are always opposite at any given time) so the two of them gives you 240v.
480 is the same thing. It's just for sites that need a lot of power or have big motors to run. That place will have a small transformer somewhere to cut it down to 240/120 for the stuff that needs it.
If you were an industrial shop, you might get what they call three phase power where you have 3 hot wires. That's a way to run motors more efficiently but it makes it kinda complicated to explain. It's why you see some things that say they're made for 240/208 volts. In three phase if you get 120v from the low voltage wires, you only get 208 from the high voltage pair.

Answer 3

In the US, all voltage enters the home at 120. If an appliance requires more, than more circuits are run to it. Thus, a 240 volt appliance, like an electric clothes dryer, will have two circuits running to it, and a double circuit-break on the electrical panel.

Voltage is 7,200 in the big overhead lines. Those tall cylinders you see on the side of the poles are transformers that step the voltage down to 120. They use 7,200 because it travels long distances better.

Answer 4

too complicated to explain well on such small space. Three phase comes in normally on four wires. Lets say one line is (L1)hot, another line is (L2)hot, and the third line is (L3)hot also known as the wild leg, with the forth line being the neutral. Connect L1 or L2 and the neutral and you get 120V, single phase. Connect L3 and neutral and you get 208V. Connect L1and L2 and you get 240V. Connect all three and you get 240 3-phase. Step it up and the same thing but with 277/480. L(1,2 or 3) to neutral and you get 277V. L to L is 480. All three 480 3-phase. Hope this helps.

Answer 5

with a step-up transformer

something like
http://www.radioshack.com/product/index.jsp?productId=2104179&cp=&origkw=transformer+240&kw=transformer+240&parentPage=search

Answer 6

the power companys transformer