Question

Generator is rated 18KVA at 0.7 pf lagging. Terminal voltage is fixed at 600 volts. Synchronous reactance is Xd is 15 ohms. Initial current Ia is 20 amps at 30 degrees lagging.

Here is part of what was assumed that you would know.

Vt is not changing.

Ei = Vt + j Ia Xd

The control knob for the field current, If controls directly the magnitude of Ei. If the knob is moved from 1.00 to 1.45, then the magnitude of Ei would increase from where it was to a magnitude of 1.45 x that value.

The Power Turbine knob Pt, controls directly the output Power P.   If it goes from 1.00 to 1.25, the P is increased to 1.25 x what it was.

You have 5 cases. You are expected to provide 6 items of information for each case:

setting of Ia control knob.     setting of Pt control knob.    Magnitude of Ei Power angle little delta    The Real Power output P The reactive power output Q

Case A knobs at 1.00 and 1.00   Info provided at the top. Find the other 4 items E, delta, P, Q

Case B If knob increased to 1.10    Pt knob still at 1.00 Find the other 4 items

Case C   If knob at 1.00   Pt knob increased to 1.20.   Find the other 4 items

Case D   Only one of the two knobs is changed. Which one is it to make Q go to zero? Find the missing 4 other values.

Case E    You want to get the generator to provide its Rated values given at the top. Determine all 6 parameters.

Answer 1