Question

A 480 V, 50 Hz, Y-connected six-pole synchronous generator has a per-phase synchronous reactance of 1.0
Ω. Its full-load armature current is 60 A at 0.8 PF lagging. Its friction and windage losses are 1.5 kW and
core losses are 1.0 kW at 60 Hz at full load. Assume that the armature resistance (and, therefore, the I2R
losses) can be ignored. The field current has been adjusted such that the no-load terminal voltage is 480 V.
a. What is the speed of rotation of this generator?
b. What is the terminal voltage of the generator if :

i. ii. iii.

it is loaded with the rated current at 0.8 PF lagging; it is loaded with the rated current at 1.0 PF; it is loaded with the rated current at 0.8 PF leading.

c. What is the efficiency of this generator (ignoring the unknown electrical losses) when it is operating
at the rated current and 0.8 PF lagging?
d. How much shaft torque must be applied by the prime mover at the full load? how large is the induced
counter-torque?
e. What is the voltage regulation of this generator at
i. 0.8 PF lagging ii. at Unity PF iii. at 0.8 PF leading?
a. The figure below is a set of Synchronous Generator and Synchronous Motor. The ratings of the
machines are as follows:
Synchronous Generator: . 3ph, 1.0 MVA, 2.3kV, 50Hz, 0.85 lagging power factor, Xs =0.9 pu
Synchronous Motor: 3ph, 0.5 MVA, 2.3kV, 50Hz, 0.85 leading power factor, Xs =0.8 pu
The generator is equipped with a voltage regulator which maintains the terminal voltage at the rated value.
The motor delivers 500 hp and it field current is adjusted to make it operate at unity power factor.

i. ii. iii.

Determine the synchronous reactance in ohms. Determine the excitation voltage of each machine. Draw the phasor diagrams

a. The figure below is a set of Synchronous Generator and Synchronous Motor. The ratings of the
machines are as follows:
Synchronous Generator: . 3ph, 1.0 MVA, 2.3kV, 50Hz, 0.85 lagging power factor, Xs =0.9 pu
Synchronous Motor: 3ph, 0.5 MVA, 2.3kV, 50Hz, 0.85 leading power factor, Xs =0.8 pu
The generator is equipped with a voltage regulator which maintains the terminal voltage at the rated value.
The motor delivers 500 hp and it field current is adjusted to make it operate at unity power factor.

The following test results are obtained for a 3ph, 25 kV, 750 MVA, 50 Hz, 3600rpm, star-connected
synchronous machines at rated speed.

i.	Determine the unsaturated and saturated values of the synchronous reactance in ohms and pu. If a short-circuit test is performed at constant field current 1500 A but at different speeds; 1000, 2000, 3000 and 3600 rpm. Determine the short-circuit current at these speeds above. Determine the field current if the synchronous machine delivers rated MVA to an infinite bus at 0.9 lagging power factor
ii. iii.

If=1500A VLL(Open circuit)=25KV, IA(open circuit test)=10000A,VLL(air gap line)=30KV

g. Calculate the capacitance of a square parallel plate capacitor having two
dielectrics εr1=2.5 and εr2=3.5 each comprising one half of the area between
the plates. The area of a plate is 4.0 x 104 cm2 and the two plates separated by
a distance of 20mm.
h. If a 24V volts electric potential is applied across the terminals of this
capacitor described above, find the electric potential energy stored in the
capacitor.

please answer these for me

Answer 1