I can't understand the whole process of using the field current in the generator to control the reactive power supplied by the generator to the system. In my reference, it says:

"The first constraint on the generator is that the power must remain constant when IF is changed."

But I don't understand how that is possible since the power into a generator (ignoring losses) is given by the equation:

P = Tind * Ï

And the torque is give by this:

Tind = k(Br x Bnet)

Being a cross product.
k = constant
Br = magnetic flux density of rotor
Bnet = net magnetic flux density.

Since we are increasing the field current, thus increasing the torque induced. Aren't we increasing the power?

 

Frank,

Can you tell us what reference you are citing?

Are you familiar with the power triangle? Excitation (field current) controls the length of the VAr component, and the torque provided by the prime mover driving the generator controls the length of the Watt component.

Are you certain your reference is for a synchronous generator, and not for an induction generator?