Torque angle and power factor of generator

[Idea04]

I need someone to clarify for me how an increase in torque angle in an ac generator increases the power factor. Does the torque from the rotor force the current in phase with the voltage on the stator.

 

[subtech]

This is best shown with a diagram, but I try to do this with a simple description.
Picture the stator windings around the inner circumference of the machine housing, each phase winding has a "reference" mark midway along its distribution. The rotating magnetic field emanating from the rotor windings also has such a reference mark at the center of its "North pole". (the peak point of its influence) When the machine is operated at unity power factor, these two reference marks are aligned, and torque angle is zero degrees. Adjusting the excitation causes the torque angle to change. If excitation is increased, we say that the torque angle is influenced positively, meaning that the rotor reference mark advances proportionally in the direction of rotation and machine outputs reactive component into the system.(the machine is inductive) Conversely, if excitation is decreased from unity value then the torque angle is influenced negatively, meaning the rotor reference mark moves proportionally in the direction opposite of rotation and the machine will absorb reactive component from the system. (the machine is capacitive)
I hope this helps.