What is the principle behind measuring power in 3 phase systems using coils?

[canicon25]

Can anyone point me to a good site that explains current induction, specifically when a coil is placed around an energized, current carrying conductor? I would like to understand this principle to understand how power can measured in 3 phase power systems by using coils as a measuring element.

 

[K^2]

Try this: Induction Law[/url].

Power is then just V*I, like for any other circuit.