Question

A 3-phase 480V, 4-pole, 60Hz, Delta- connected synchronous generator with the OCC shown here has an armature resistance of RA-0015Ω and 400 synchronous reactance ofX, 0.1.2. At full load, the machine supplies 1200A at 0.8PF lagging. Under full-load conditions, the friction and windage losses are 40kW, and the core losses are 30kW. Ignore field 300 200 circuit losses. a) If the generator is operated at full load, how much field current is required to keep the terminal 100 voltage constant at 480V. What 1 70 10 40 500 1090 is the machine's overall Field currenl, A efficiency in this case? B) Draw the phasor diagram for full load condition. C) If the generator's load were suddenly disconnected from the line, what would be the value of the terminal voltage?

Answer 1

(C)

3. Et L& 480 Lo。 「2 outpott losse 792 4 79 13 40+30 Phoor Doe

In case of open circuit i.e. load is disconnected then generator terminal voltage i.e. excitation emf will appear across the load because there is no current in the circuit.