6. A 3-phase, star-connected turbo-alternator with a synchronous reactance of 8 ohms per phase delivers 200 A at unity power-factor when connected to 11 kV constant frequency busbars. If the throttle is held constant while the excitation e.m.f. is increased by 30% determine the new current and power-factor. The excitation e.m.f. is now held constant at the new value and the steam supply is gradually increased. Find the value of output power at which the machine will break from synchronism and the operating power-factor under these conditions. Neglect armature resistance. (Answer: 324A; 0-622 lag; 19-8 MW; 0-6 lead)