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Another question..

 
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This is another question that has been bugging mee for quite along time.
Why are all the electrical voltages (household as well as power station) in multiple of 11. i.e 110V, 11000V/22000V etc.???
 
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it might have something to do with "step-up" or "step-down" transformers... the voltage is sent from the power station along the power lines as a very high voltage and then it is stepped-down by a series of transformers until it gets to the 110/220 that is used in your house.
transformers step-up/down the voltage by using more/less coils of wire on one side than is on the other. this is usually a multiple like 1/2 1/4... so, if you have 220 into a 2/1 transformer, it will come out as 110.
 
Greenhorn
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Originally posted by Greg Harris:
transformers step-up/down the voltage by using more/less coils of wire on one side than is on the other. this is usually a multiple like 1/2 1/4... so, if you have 220 into a 2/1 transformer, it will come out as 110.


That is true.. but why transmit at such odd numbers? Why not a nice round number? Why can't we have household voltages at 100V and high power transmissions at some 10^n? Any thoughts on this?
 
Jim Bertorelli
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Greg, 220->110 is understantable. But as Naveen said, why have 220 in the first place? Why not 200?
 
Greg Harris
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well, actually it is 120 here in the US... and it has to do with the fact that our stuff operates at 60Hz. of course, you know that P=I*E (Power = Current * Voltage), so because we operate at 60Hz, and our voltage is 120, our current is obviously 60/120 = 0.5 amps.
 
Greg Harris
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i guess i should expand a little:
AC (alternating current) works because it alternates across a frequency range... unlike a flashlight battery which just discharges into the bulb.
so, way back when they started making devices that operated on AC current, they made 60Hz the standard. 0.5 ams is a fairly safe level, so the average person is not going to get killed if they stick their finger in the socket. because we needed 60Hz and did not want the amps to be above 0.5, we needed to get the voltage down to 120.
 
Jim Bertorelli
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Greg, I know a little bit about P=IE and I think 60Hz has nothing to do with it. It's just the frequency of the AC wave.
Current in the appliances is not constant. It depends on power of the applicance. A 60Watt bulb will draw 60/120 = .5A but a 1200Watt AC will draw 1200/120 = 10 Amps.
BTW, if you look at the applicances, you'll see the voltage rating as 110V not 120V
 
Jim Bertorelli
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In fact, to keep the current very less in the transmission wires, they keep a very high voltage accross power transmission stations.
 
Greg Harris
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yea, i was making all of that up. sounds good if you do not know what i am talking about, though.
the high voltage and the electromagnetic field generated by such high voltages is another reason why the transmission lines are so high... that is also why they have the triangle separators between the wires.
 
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Originally posted by Jim Bertorelli:

BTW, if you look at the applicances, you'll see the voltage rating as 110V not 120V


And on some multi-voltage devices, you can switch between 110V and 120V. Japan uses 110V as opposed to our 120V, for example.
 
Greg Harris
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>And on some multi-voltage devices, you can switch between 110V and 120V. Japan uses 110V as opposed to our 120V, for example.
thanks, Jason... i was about to find a link to prove that i am not totally crazy, but you took care of it. i know i have been out of the Navy for 3 years, but i did not forget everything that i learned as an Electronic Warfare Specialist!
 
Jim Bertorelli
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Hey! come on Greg, you are not crazy
 
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Interesting question.
You'll remember I'm sure that in the 1870's-1880's there was the big fight between Edison-Swan vs. Westinghouse-Tesla.
Edison pushed DC as the way to go.
Westinghouse pushed AC.
I think Tesla patented the 1st AC generator, and the patent was leased by Westinghouse.
The answer probably has to do with what Tesla could actually get to work reliably with materials at hand .......
Regards, Guy
 
Greg Harris
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Originally posted by Jim Bertorelli:
Hey! come on Greg, you are not crazy


thanks... i will get back to you sometime next semester when i am taking PHYS 3340 (Electronics Physics).
 
mister krabs
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Originally posted by Jim Bertorelli:
BTW, if you look at the applicances, you'll see the voltage rating as 110V not 120V

In the US we use 120V but what comes out of the socket can be a range of 110-120V due to conditions at the power plant, power lines, etc.
 
Thomas Paul
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Tesla's opinion was that 60Hz alternator was the most efficient one, so he insisted that Westinghouse Company also ought to adopt its alternator to 60Hz.
 
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What about here i Sweden (and rest of Europe?) where we use 230V? (some years ago it were 220V but they changed it to 230V...) Yes, then we also have a lower freqency (I think it is 50Hz).
But why such a large differences and how does that affect the way elecrical stuff is built?

/Andreas
 
Thomas Paul
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I think that is why Sweden has such a high suicide rate.
 
Andreas Johansson
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Originally posted by Thomas Paul:
I think that is why Sweden has such a high suicide rate.


Threadkiller... =(
 
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Jim,
in response to your original question why 110. I read some of the responses you have recieved. I have a two year degree in electronics and telecommunications. A more likely answer is the fact that a standard had to be set by power companies in order to regulate power consumption. It's more likely that the standard was based on the decimal system which was already in place as electronics developed. The decimal system is also the basis for computer language. The ones and zeros in computer language are all based off the decimal system. In order to make the computer language faster and more efficient a multiples based system was adopted; however, it all began on the decimal system.
Bobcat
 
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