A question for real sparks (Not DIY)

[Softus]

Did I miss something juicy?

 

[ban-all-sheds]

someone asked this a few weeks ago. someone will give you a link. ended up spanning about 15 pages in 2 days

Didn't that thread end up getting deleted when the OP got all offensive?

Why on earth should someone have got all offensive about 3-phase power?

And gafferson - why do you think that only electricians can tell you why we have 3-phase?

 

[TheGaffersSon]

someone asked this a few weeks ago. someone will give you a link. ended up spanning about 15 pages in 2 days

Didn't that thread end up getting deleted when the OP got all offensive?

Why on earth should someone have got all offensive about 3-phase power?

And gafferson - why do you think that only electricians can tell you why we have 3-phase?

Well not ONLY electricians, but mainly electricians. I wouldn't ask a plumber about decking screws now would I ?

 

[Spark123]

Many thanks to all that have posted so far.

Can you tell me, why are 3-phases used to connect to a metre. I fitted one the other day, and didn't like not knowing why I did so.

If you have a 3phase supply you'll need a 3 phase meter or 3 single phase meters, if you have a single phase supply a single phase meter will do.

Another question. I may be wrong but is 3-phase used, because the magnetic field produced can make objects rotate by all three at 120 degrees pulling it towards them?

Which is why a 3phase motor is a lot more efficient than its single phase counterpart.

I was told if you fit a 3 phase item incorrectly (ie the wrong way round) it can work in reverse. I assumed this was because the magnetic fields would be different.

To make a 3phase motor spin the opposite way you swop two of the supply phase wires to it over.

 

[plugwash]

Indeed so, but is the power waveform not also sinusoidal?

If the power waveform was purely sinusoidal then you'd never get any power through (which btw is what happens if you connect a perfect inductor or capacitor to an AC supply, theres voltage and current but no net power)

if we assume a resistive (power factor 1) load then the power waveform will have a constant component (the average) plus a sinusoidal component that will cause it to vary beween 0 and twice the average.

 

[Nige F]

someone asked this a few weeks ago. someone will give you a link. ended up spanning about 15 pages in 2 days

Didn't that thread end up getting deleted when the OP got all offensive?

Why on earth should someone have got all offensive about 3-phase power?

And gafferson - why do you think that only electricians can tell you why we have 3-phase?

Well not ONLY electricians, but mainly electricians. I wouldn't ask a plumber about decking screws now would I ?

No but you could ask me about caulking decking on a ship using a caulking iron similar to leaded soil pipe joints.....one use for old rope

 

[Jaymack]

Do a search; and all will usually be explained: -

http://en.wikipedia.org/wiki/Three-phase_electric_power

Jaymack

 

[soontobe]

kids going back to scool monday, need to go in tomorro, or i will be sinesoidal!

 

[Spark123]

Did you see the date of the original post?

 

[Taylortwocities]

So he probably knows it ALL now - after a year.

Probably he knows the difference between a metre and a meter too