house outlet ac power

[Capernicus]

I hear that America is 120v,  and Australia is 240v.

But is that the distance between the most positive point of the wave and most negative point.   so its actually 60 high and 60 low, for a total of 120,  or is it 240 + to -  for 120 volt america.

So is it the same for australia - excepts its double?

[BeBuLamar]

I guess you need to learn a little bit about basic electricity. The 120V or 240V isn't about distances.

[Capernicus]

there is a positive cycle and negative cycle is there not?

So im asking whats the peak negative and peak positive volts,  of the live wire.

[BeBuLamar]

The peak for the 120VAC in the USA is +170 to -170. For the 240V it's +339 to -339.

[Gyro]

The 120V and 240V are RMS voltages, not Peak to Peak.  https://www.electronics-tutorials.ws/accircuits/rms-voltage.html

[Capernicus]

thankyou.   RMS.      yes I didnt know this.

So 120 RMS has to do with summing it up over time?

If its a square wave wouldnt you get 120 volts dc with less peak?

[Shock]

[mcz]

thankyou.   RMS.      yes I didnt know this.

So 120 RMS has to do with summing it up over time?

If its a square wave wouldnt you get 120 volts dc with less peak?

For a square wave you have the luxury of the amplitude beeing equal to the RMS voltage. So 120Vp (single peak, not peak to peak!) get you 120Vrms.

[Capernicus]

Yeh I see now.   because the negative half is a different phase than the positive half, they dont add up to double.   

[bdunham7]

Yeh I see now.   because the negative half is a different phase than the positive half, they dont add up to double.   

Except in the US, where it does. 

https://en.wikipedia.org/wiki/Split-phase_electric_power

[David Hess]

The US uses split phase, so 120VAC is 120 volts RMS, 170 volts peak or 340 volts peak-to-peak, centered around neutral/ground, and 240VAC is 240 volts RMS, but made from two 120VAC outputs which are 180 degrees out of phase.

At the transformer, the secondary is 240VAC with a center tap attached to neutral, and neutral is attached to Earth ground at the distribution panel.  Inside the building, the 120VAC sockets are distributed between the two 180 degree phases, which means in theory 240VAC can be regained by using the hot lead from two different sockets, not that I would ever have done that.  Also, I have never wired a duplex output with one phase on one outlet and the other phase on the other outlet.  That is my story and I am sticking to it.

[Shock]

Yeh I see now.   because the negative half is a different phase than the positive half, they dont add up to double.   

Same phase just second half of the cycle. The potential for current is induced by rotating a magnet past a coil. So it goes to becoming very positive in the first half of the rotation cycle to very negative in the second half.

[Terry Bites]

OK.
In the US and the voltage available in the home is 220 or 110. This is because two phase domestic power is the norm there. 

https://upload.wikimedia.org/wikipedia/commons/c/cc/World_Map_of_Mains_Voltages_and_Frequencies%2C_Simplified.png

Your basic outlet is 110V and you get bigger 220V outlets for stoves and such.
Why mix it up, I dont know. Its was not safer back in the day. GFCIs (RCDs) makes this less relavent now of course.
In most countries you typically get 230-250 so you dont need mad amounts of copper and you only need a single plug type.

[bdunham7]

Why mix it up, I dont know. Its was not safer back in the day. GFCIs (RCDs) makes this less relavent now of course.

Probably for compatibility with early systems that were actually 110V only in single-unit houses.  What do you mean about safety and plugs?  You still have half the voltage phase-to-ground that you have in EU/Aus/etc.  And most 240V devices don't plug in at all and those that do (dryers, say) use a much larger plug than would be practical for ordinary appliances, so you would still have to have different plugs.

[TimFox]

The US NEMA connectors used for 120 V, 240 V, and three-phase wall sockets and cable plugs are well-defined and required for conformance to NEC electrical codes.

[IanB]

OK.
In the US and the voltage available in the home is 220 or 110. This is because two phase domestic power is the norm there. 

https://upload.wikimedia.org/wikipedia/commons/c/cc/World_Map_of_Mains_Voltages_and_Frequencies%2C_Simplified.png

Your basic outlet is 110V and you get bigger 220V outlets for stoves and such.

Fortunately for me, my home has 240 V and 120 V. This enables me to use a 240 V electric kettle imported from the UK at full power.

Why mix it up, I dont know. Its was not safer back in the day. GFCIs (RCDs) makes this less relavent now of course.
In most countries you typically get 230-250 so you dont need mad amounts of copper and you only need a single plug type.

According to this excellent YouTube presenter, the reason goes back to the pioneering days of electricity, when Edison invented the carbon filament electric lightbulb. It was very difficult to make carbon filament lamps work from higher voltages than about 120 V or so, which caused the supply voltage to be set at this level.

Later on, the tungsten filament lamp was introduced, which could easily be made to operate at 240 V, but by that time there were so many carbon filament lamps in use in America that it was very difficult to change the standard, so it stuck, even when DC moved over to AC.

In the rest of the world, it was recognized that higher voltages permitted lower currents and thus less copper in the wiring, and carbon filament lamps were less prevalent, so they settled on 220 to 240 V and everyone went straight to tungsten lamps.

[tooki]

OK.
In the US and the voltage available in the home is 220 or 110. This is because two phase domestic power is the norm there. 

https://upload.wikimedia.org/wikipedia/commons/c/cc/World_Map_of_Mains_Voltages_and_Frequencies%2C_Simplified.png

Your basic outlet is 110V and you get bigger 220V outlets for stoves and such.
Why mix it up, I dont know. Its was not safer back in the day. GFCIs (RCDs) makes this less relavent now of course.
In most countries you typically get 230-250 so you dont need mad amounts of copper and you only need a single plug type.

Mains voltage in USA hasn’t been 110/220V for the better part of a century. It’s 120/240V.

[fordem]

In the US and the voltage available in the home is 220 or 110. This is because two phase domestic power is the norm there. 

US residential power is not two phase, it's single phase, split phase - think center tapped transformer and you'll get the big picture.

[Brumby]

Here's a question I've been meaning to ask for a while....

What difference is there between two phase and split phase?

(I have an answer, but I'd like to see what others think.)

[Gyro]

I'd have though that two phase would be something like what is fed to the windings of an induction motor - one phase being directly driven and the other phase being shifted by the run capacitor.

I can't really think of many things that aren't either three (or more) phases, or single phase.


P.S. I think the clearest definition of US mains is 240V Centre tapped - that's how we normally refer to transformer secondaries (which is what it is).

[Shock]

Single, two and three phase systems are 120 degrees out of phase. Split phase is 180 degrees, they seem to use a center tapped transformer.

[Capernicus]

Why isnt all ac power a square wave,  makes it all simpler.

[BeBuLamar]

It's not easy to build a generator that delivers square wave. Yeah with inverter from DC power it's easy but not so with an engine or other mechanical source turning an alternator.

[Brumby]

Single, two and three phase systems are 120 degrees out of phase.

How can a single phase be out of phase?

Single, two and three phase systems are 120 degrees out of phase.

Why 120º ?  Could be any angle in the range of 0º < Φ < 360º, couldn't it?

Single, two and three phase systems are 120 degrees out of phase.

That's the sensible approach.

Split phase is 180 degrees, they seem to use a center tapped transformer.

I believe they do.

[Brumby]

Why isnt all ac power a square wave,  makes it all simpler.

Define "all".

.... because all I'm coming up with is a bucketload of problems!!