A synchronous motor is drawing 90 amps from 240V, 3 phase line at 0.8 pf leading with field current adjusted to 1.2 amps. The synchronous machine Xd is 1.3 ohms. Find
a). The power angle delta
b). The machine constant (m) (similar to k')
c). Assuming no change in the mechanical load, approximately what value of field current will result in a unity pf?