Synchronous Machines · Electrical Machines · GATE EE

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Marks 1

GATE EE 2022
A star-connected 3-phase, 400 V, 50 kVA, 50 Hz synchronous motor has a synchronous reactance of 1 ohm per phase with negligible armature resistance. T...
GATE EE 2018
In a salient pole synchronous motor, the developed reluctance torque attains the maximum value when the load angle in electrical degrees is
GATE EE 2017 Set 1
A three-phase, 50Hz, star-connected cylindrical-rotor synchronous machine is running as a motor. The machine is operated from a 6.6 kV grid and draws ...
GATE EE 2017 Set 2
If a synchronous motor is running at a leading power factor, its excitation induced voltage (Er) is
GATE EE 2014 Set 1
A star connected 400 V, 50 Hz, 4 pole synchronous machine gave the following open circuit and short circuit test results: Open circuit test: VOC = 40...
GATE EE 2014 Set 3
In a synchronous machine, hunting is predominantly damped by
GATE EE 2011
A three-phase, salient pole synchronous motor is connected to an infinite bus. It is operated at no load a normal excitation. The field excitation of ...
GATE EE 2008
Distributed winding and short chording employed in AC machines will result in
GATE EE 2008
In a stepper motor, the detent torque means
GATE EE 2007
A three phase synchronous motor connected to ac mains is running at full load and unity power factor. If its shaft load is reduced by half, with field...
GATE EE 2006
A synchronous generator is feeding a zero power factor (lagging) load at rated current the armature reaction is
GATE EE 2005
In relation to the synchronous machines, which one of the following statements is false?
GATE EE 2004
For a given stepper motor, the following torque has the highest numerical value.
GATE EE 2004
The following motor definitely has a permanent magnet rotor
GATE EE 2003
Curves X and Y in Figure denote open circuit and full-load zero power factor (zpf) characteristics of asynchronous generator. Q is a point on the zpf ...
GATE EE 2003
A stand-alone engine driven Synchronous generator is feeding a partly inductive load. A capacitor is now connected across the load to completely nulli...
GATE EE 2001
It is desirable to eliminate 5th harmonic voltage from the phase voltage of an alternator. The coils should be short-pitched by an electrical angle of...
GATE EE 2001
Figure shows the magnetization curves of an alternator at rated armature current, unity power factor and also at no load. The magnetization curve for ...
GATE EE 2001
Xd, Xd' and Xd" are steady stated-axis synchronous reactance, transient d-axis reactance and sub-transient d-axis reactance of a synchronous machine r...
GATE EE 2000
The phase sequence of a three-phase alternator will reverse if
GATE EE 1999
Higher synchronous reactance is preferred in the present day alternators, because one can have
GATE EE 1998
A synchronous generator connected to an infinite bus is overexcited. Considering only the reactive power, from the point of view of the system, the ma...
GATE EE 1996
During hunting of synchronous motor
GATE EE 1996
In Figure. The characteristic that corresponds to the variation of synchronous reactance of synchronous motor with field current is ...
GATE EE 1995
A synchronous motor on load draws a current at a leading power factor angle $$\phi$$. If the internal power factor angle – which is the phase angle be...
GATE EE 1992
The torque angle of a synchronous machine operating from a constant voltage bus, is usually defined as the space angle between
GATE EE 1992
The developed electromagnetic force and or torque in electro $$-$mechanical energy conversion systems act in a direction that tends

Marks 2

GATE EE 2017 Set 1
Two parallel connected, three-phase, $$50Hz,$$ $$11kV,$$ star-connected synchronous machines $$A$$ and $$B,$$ are operating as synchronous condensers....
GATE EE 2017 Set 2
A $$3$$-phase, $$2$$-pole, $$50$$ $$Hz,$$ synchronous generator has a rating of $$250$$ $$MVA,$$ $$0.8$$ $$pf$$ lagging. The kinetic energy of the mac...
GATE EE 2017 Set 2
Two generating units rated $$300$$ $$MW$$ and $$400$$ $$MW$$ have governor speed regulation of $$6\% $$ and $$4\% $$ respectively from no load to full...
GATE EE 2017 Set 2
A $$25$$ $$kVA,$$ $$400$$ $$V,$$ $$\Delta $$ - connected, $$3$$-phase, cylindrical rotor synchronous generator requires a field current of $$5$$ $$A$$...
GATE EE 2016 Set 1
A three-phase, $$50$$ $$Hz$$ salient-pole synchronous motor has a per-phase direct-axis reactance $$\left( {{X_d}} \right)$$ of $$0.8$$ $$pu$$ and a p...
GATE EE 2015 Set 2
A three-phase, $$11$$ $$kV,$$ $$50$$ $$Hz,$$ $$2$$ pole, star connected, cylindrical rotor synchronous motor is connected to an $$11$$ $$kV,$$ $$50$$ ...
GATE EE 2014 Set 1
A three phase synchronous generator is to be connected to the infinite bus. The lamps are connected as shown in the figure for the synchronization. Th...
GATE EE 2014 Set 3
A non-salient pole synchronous generator having synchronous reactance of $$0.8$$ $$pu$$ is supplying $$1$$ $$pu$$ power to a unity power factor load a...
GATE EE 2014 Set 2
There are two generators in a power system. No-load frequencies of the generators are $$51.5$$ $$Hz$$ and $$51$$ $$Hz,$$ respectively, and both are ha...
GATE EE 2014 Set 2
A $$20$$-pole alternator is having $$180$$ identical stator slots with $$6$$ conductors in each slot. All the coils of a phase are in series. If the c...
GATE EE 2014 Set 2
A synchronous generator is connected to an infinite bus with excitation voltage $${E_f} = 1.3\,pu.$$ The generator has a synchronous reactance of $$1....
GATE EE 2011
The direct axis and quadrature axis reactances of a salient pole alternator are $$1.2$$ $$p.u$$ and $$1.0$$ $$p.u$$ respectively. The armature resista...
GATE EE 2010
A $$50$$ $$Hz$$ synchronous generator is initially connected to a long lossless transmission line which is open circuited at the receiving end. With t...
GATE EE 2010
A separately excited $$dc$$ machine is coupled to a $$50Hz,$$ three-phase, 4-pole induction machine as shown in the figure. The dc machine is energize...
GATE EE 2009
A field excitation of $$20A$$ in a certain alternator results in a armature current of $$400$$ $$A$$ in short circuit and a terminal voltage of $$2000...
GATE EE 2008
A synchronous motor is connected to an infinite bus at $$1.0$$ $$p.u$$ voltage and draws $$0.6$$ $$pu$$ at unity power factor. Its synchronous reacta...
GATE EE 2008
A synchronous motor is connected to an infinite bus at $$1.0p.u$$ voltage and draws $$0.6$$ $$pu$$ at unity power factor. Its synchronous reactance ...
GATE EE 2007
A $$100$$ $$kVA$$, $$415V,$$ star connected synchronous machine generates rated open circuit voltage $$415V$$ at a field current of $$15A.$$ The shor...
GATE EE 2007
A $$3$$ phase, $$3$$ stack, variable reluctance stepper motor has $$20$$ poles on each rotor and stator stack. The step angle of this stepper motor is...
GATE EE 2006
A $$3$$-phase $$4000$$ $$V,$$ $$5$$ $$kW,$$ star connected synchronous motor having an internal reactance of $$10$$ $$ohms$$ is operating at $$50\% $$...
GATE EE 2006
A $$4$$ pole, $$50$$ $$Hz,$$ synchronous generator has $$48$$ slots in which a double layer winding is house. Each coil has $$10$$ turns and is short...
GATE EE 2006
A $$4$$ pole, $$50$$ $$Hz,$$ synchronous generator has $$48$$ slots in which a double layer winding is house. Each coil has $$10$$ turns and is short...
GATE EE 2005
A $$1000$$ $$kVA,$$ $$6.6$$ $$kV,$$ $$3$$-phase star connected cylindrical pole synchronous generator has a synchronous reactance of $$20\Omega .$$ Ne...
GATE EE 2005
A $$1000$$ $$kVA,$$ $$6.6$$ $$kV,$$ $$3$$-phase star connected cylindrical pole synchronous generator has a synchronous reactance of $$20\Omega .$$ Ne...
GATE EE 2004
The synchronous speed for the seventh space harmonic $$mmf$$ wave of a $$3$$-phase, $$8$$ pole, $$50$$ $$Hz$$ induction machine is
GATE EE 2004
Two $$3$$-phase, $$Y$$-connected alternators are to be paralleled to a set of common bus bars. The armature has a per phase synchronous reactance of $...
GATE EE 2004
A $$400$$ $$V,$$ $$50$$ $$kVA,$$ $$0.8$$ $$pf$$ leading delta connected, $$50$$ $$Hz$$ synchronous machine has a synchronous reactance of $$2$$ $$ohm$...
GATE EE 2004
For a $$1.8$$ degree, $$2$$-phase bipolar stepper motor, the stepping rate is $$100$$ steps/second. The rotational speed of the motor in $$rpm$$ is
GATE EE 2004
A $$500$$ $$MW$$ $$3$$-phase $$Y$$-connected synchronous generator has a rated voltage of $$21.5kV$$ at $$0.85$$ $$pf.$$ The line current when operati...
GATE EE 2004
A hydraulic turbine having rated speed of $$250$$ $$rpm$$ is connected to a synchronous generator. In order to produce power at $$50$$ $$Hz,$$ the num...
GATE EE 2003
A $$4$$-pole, $$3$$-phase, double layer winding is housed in a $$36$$-slot stator for an $$ac$$ machine with $$60$$ degree phase spread. Coil span is ...
GATE EE 2002
The flux per pole in a synchronous motor with the field circuit ON and the stator disconnected from the supply is found to be $$25$$ $$mWb.$$ When the...
GATE EE 2001
A star-connected 440 V, 50 Hz alternators has per phase synchronous reactance of 10 Ω. It supplies a balanced capacitive load current of 20 A, as show...
GATE EE 2000
A single-phase, 2000 V alternator has armature resistance and reactance of 0.8 ohms and 4.94 ohms respectively. The voltage regulation of the alternat...
GATE EE 1999
A three phase alternator is wound with a 60 degree phase-spread armature windings and develops 300 kVA. If the armature is reconnected utilizing all t...
GATE EE 1998
The armature of a single phase alternator is completely wound with T single turn coils distributed uniformly. The induced voltage in each turn is 2 Vo...
GATE EE 1997
A single-phase alternator has a synchronous reactance of $$2$$ $$ohms$$ and negligible resistance. If it supplies $$10$$ $$A$$ to a purely capacitive ...
GATE EE 1993
A three phase alternator has negligible stator resistance. A short circuit test is conducted on this alternator. At a particular speed a field current...
GATE EE 1993
Two $$550$$ $$kVA$$ alternators operate in parallel to supply the following loads $$(i)$$ $$250$$ $$kW$$ at $$0.95$$ power factor lag $$(ii)$$ $$100$...
GATE EE 1993
A synchronous motor operates at $$0.8$$ $$p.f.$$ lagging. If the field current of the motor is continuously increased $$(1)$$ the power factor decrea...

Marks 5

GATE EE 2002
A $$415$$ $$V,$$ $$2$$ pole, $$3$$ phase, $$50$$ $$Hz,$$ star connected, non-salient pole synchronous motor has synchronous reactance of $$2\,\Omega $...
GATE EE 2001
A $$50$$ $$kW$$ synchronous motor is tested by driving it by another motor. When the excitation is not switched on, the driving motor takes $$800$$ $$...
GATE EE 2001
Two identical synchronous generators, each of $$100$$ $$MVA,$$ are working in parallel supplying $$100$$ $$MVA$$ at $$0.8$$ lagging $$p.f.$$ at rated ...
GATE EE 2000
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 suc...
GATE EE 1997
A $$5MVA$$, $$11kV$$, $$3$$-phase star connected alternator is synchronized to the bus bars and is operating with an induced $$EMF$$ of $$125\% $$ of ...
GATE EE 1996
The per unit voltage of two synchronous machines connected through a lossless line are $$0.95\,\,\angle \,{10^0}\,\,$$ and $$1.0\,\,\angle \,{0^0}\,\,...
GATE EE 1995
The distribution factor for a $$36$$ slot stator with three-phase, $$8$$-pole winding, having $${120^ \circ }$$ phase Spread, is _________
GATE EE 1992
Figure depicts the load characteristics of an constant speed. Match the following sets of operating conditions with the given characteristics. Disrega...
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