theory question!!!???

[oui33]

hello!!

i would like to help me!!
(my english are not good.)
1.why we prefer the 3phase systems to produce energy and not the 2phase???

2.which are the differences between them??

[prateeksikka]

hi there!
Three phase and in general multiphase systems are generally prefered to  ensure the smoothness by which load runs especially a motor.Knocking is generally less of a problem in 3 phase motors than 1 phase motors.

[audioguru]

Having more pistons makes a motor run smoothly. ;D ;D

[prateeksikka]

hi audioguru!
Isnt it true what i said?I have read and in fact seen 3 phase motors running much more smmothely! ;D
pistons? :o

[Kevin Weddle]

It is interesting that when I think of two and three phases I think of that silly sinusoidal picture of sine waves superimposed. How are you supposed to know what the voltage is actually doing. Does it add? Does it subtract? A total conspiracy.

Here's something that comes to mind. Whenever you have two signal coming together, the voltage of the resulting signal at any given time will be somewhere in between the two signal values. If one signal goes to +5v and the other goes to -2v, the result will be somewhere in between depending on the resistors the signals are fed through. If you can remember superposition theory then you know what I am talking about.

[prateeksikka]

hi kevin!
At any instant the net voltage across load is the phasor sum of three voltages.The resulting waveform is much smoother. Thats 3 phase! better than 1 phase!
;D ;D ;D