A 480 V, 50 Hz, Y-connected six-pole synchronous generator has aper-phase synchronous reactance of 1.0
Ω. Its full-load armature current is 60 A at 0.8 PF lagging. Itsfriction and windage losses are 1.5 kW and
core losses are 1.0 kW at 60 Hz at full load. Assume that thearmature resistance (and, therefore, the I2R
losses) can be ignored. The field current has been adjusted suchthat 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 theunknown 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 thefull 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 andSynchronous Motor. The ratings of the
machines are as follows:
Synchronous Generator: . 3ph, 1.0 MVA, 2.3kV, 50Hz, 0.85 laggingpower factor, Xs =0.9 pu
Synchronous Motor: 3ph, 0.5 MVA, 2.3kV, 50Hz, 0.85 leading powerfactor, Xs =0.8 pu
The generator is equipped with a voltage regulator which maintainsthe terminal voltage at the rated value.
The motor delivers 500 hp and it field current is adjusted to makeit 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 andSynchronous Motor. The ratings of the
machines are as follows:
Synchronous Generator: . 3ph, 1.0 MVA, 2.3kV, 50Hz, 0.85 laggingpower factor, Xs =0.9 pu
Synchronous Motor: 3ph, 0.5 MVA, 2.3kV, 50Hz, 0.85 leading powerfactor, Xs =0.8 pu
The generator is equipped with a voltage regulator which maintainsthe terminal voltage at the rated value.
The motor delivers 500 hp and it field current is adjusted to makeit operate at unity power factor.
The following test results are obtained for a 3ph, 25 kV, 750MVA, 50 Hz, 3600rpm, star-connected
synchronous machines at rated speed.
| i. | Determine the unsaturated and saturated values of thesynchronous reactance in ohms and pu.
If a short-circuit test is performed at constant field current 1500A 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 deliversrated MVA to an infinite bus at 0.9 lagging
power factor |
ii.
iii. |
If=1500A VLL(Open circuit)=25KV, IA(open circuittest)=10000A,VLL(air gap line)=30KV
g. Calculate the capacitance of a square parallel plate capacitorhaving two
dielectrics εr1=2.5 and εr2=3.5 each comprising one half of thearea between
the plates. The area of a plate is 4.0 x 104 cm2 and the two platesseparated by
a distance of 20mm.
h. If a 24V volts electric potential is applied across theterminals of this
capacitor described above, find the electric potential energystored in the
capacitor.
please answer these for me
