1
GATE EE 2001
Subjective
+5
-0
Two identical synchronous generators, each of $$100$$ $$MVA,$$ are working in parallel supplying $$100$$ $$MVA$$ at $$0.8$$ lagging $$p.f.$$ at rated voltage. Initially the machines are sharing load equally. If the field current of first generator is reduced by $$5\% $$ and of the second generator increased by $$5\% ,$$ find the sharing of load ($$MW$$ and $$MVAR$$) between the generators.
Assume$${X_d} = {X_q} = 0.8\,\,p.u.$$ no field saturation and rated voltage across load. Reasonable approximations may be made.
Assume$${X_d} = {X_q} = 0.8\,\,p.u.$$ no field saturation and rated voltage across load. Reasonable approximations may be made.
2
GATE EE 2000
Subjective
+5
-0
A $$2300$$ $$V,$$ $$3$$-phase synchronous motor driving a pump is provided with a line ammeter and a field rheostat. When the rheostat is adjusted such that the $$ac$$ line current is minimum. The ammeter reads $$8.8$$ $$A.$$ What is the power being delivered to the pump, neglecting losses? How should the rheostat be adjusted so that the motor operates at $$0.8$$ leading power factor? How many $$kVARs$$ is the motor supplying to the system at this new power factor?
3
GATE EE 1997
Subjective
+5
-0
A $$5MVA$$, $$11kV$$, $$3$$-phase star connected alternator is synchronized to the bus bars and is operating with an induced $$EMF$$ of $$125\% $$ of the rated voltage. If the load current is $$500$$ $$A,$$ what is the power factor of operation? The machine has a synchronous reactance of $$5\,\,\Omega $$ and negligible resistance per phase.
4
GATE EE 1996
Subjective
+5
-0
The per unit voltage of two synchronous machines connected through a lossless line are $$0.95\,\,\angle \,{10^0}\,\,$$ and $$1.0\,\,\angle \,{0^0}\,\,$$. Match the two sides in the following
$$(a)$$ Real power of Machine $$1$$
$$(b)$$ Reactive power of machine $$1$$
$$(c)$$ Power factor of Machine $$1$$
$$(a)$$ Real power of Machine $$1$$
$$(b)$$ Reactive power of machine $$1$$
$$(c)$$ Power factor of Machine $$1$$
$$(P)$$ Positive real power
$$(Q)$$ Positive reactive power
$$(R)$$ Negative real power
$$(S)$$ Negative reactive power
$$(T)$$ Leading power factor
$$(U)$$ Lagging power factor
Questions Asked from Synchronous Machines (Marks 5)
Number in Brackets after Paper Indicates No. of Questions
GATE EE Subjects
Electric Circuits
Electromagnetic Fields
Signals and Systems
Electrical Machines
Engineering Mathematics
General Aptitude
Power System Analysis
Electrical and Electronics Measurement
Analog Electronics
Control Systems
Power Electronics