During hunting of synchronous motor

In Figure. The characteristic that corresponds to the variation of synchronous reactance of synchronous motor with field current is

A synchronous motor on load draws a current at a leading power factor angle $$\phi$$. If the internal power factor angle – which is the phase angle between the excitation e.m.f. and the current in the time phasor diagram is $$\psi$$, then the air gap excitation m.m.f lags the armature m.m.f by

The torque angle of a synchronous machine operating from a constant voltage bus, is usually defined as the space angle between