Why are the three phases leading and lagging?

Thread Starter

foolios

Joined Feb 4, 2009
163
Why do power transmission lines have three phases that are offset by 90 degrees?

And how does the power generator create three seperate phases like that? I see how the generator is depicted as generating AC but it is only showing one line. Are there 3 coils? Three generators? Three sets of magnets? What gives?

Thanks in advance
 

SgtWookie

Joined Jul 17, 2007
22,230
Why do power transmission lines have three phases that are offset by 90 degrees?
They are offset by 120°.
When you add up the three offsets, you get 360°.
And how does the power generator create three seperate phases like that? I see how the generator is depicted as generating AC but it is only showing one line. Are there 3 coils? Three generators? Three sets of magnets? What gives?
This should help explain things:
http://en.wikipedia.org/wiki/Three-phase_electric_power
Look here, too:
http://en.wikipedia.org/wiki/Induction_motor
Generators:
http://en.wikipedia.org/wiki/Electrical_generator
Alternators:
http://en.wikipedia.org/wiki/Alternator
 
Last edited:

t_n_k

Joined Mar 6, 2009
5,455
Each of the three phases is offset with respect to the other two by 120 degrees (leading in one case and lagging in the other) - not 90 degrees.

The AC generators have three similar windings which are mechanically offset in such a way as to generate the correct sinusoidal voltages with the required phase relationships.

There will be any number of web links to this subject - try Google.
 
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