Three Phase Electrcity

[thos]

Can any one help someone interested in electricity but with limited knowledge? Does each one of lines in a 400v supply carry 230v? Is it necessary to connect only 2 of these lines to say a motor in
order to receive 400v or are all 3 lines always used? And finally, why is the supply 400v rather than 690, i.e. 3 x 230?
I know that it's connected with the three coils in the alternator and the square root of 3 but it's just a bit beyond me at the moment. Any help would be greatly appreciated

 

[Marvo]

Download the pdf books on this page, the answers and many more are in there.

These books are distributed as some kinda freeware/shareware/beerware

 

[jaresquire]

Handy reference, but as a quick answer session..

Each line carries 230V against the neutral but reaches its peak or trough at a different point compared to the others (1/3 cycle before or after)
Between any two phase lines voltage is root three times phase voltage, = 398V (rms values)
Three phases are used as a motor will then always have a torque generated rather than depending on mechanical inertia to keep it spinning.