What is the phase current in phase Y and in phase B out of R-Y-B when sudden short circuit to all three phases occurs at no load? It is given that after fault current in phase R is equal (Vm Sin ωt)

Y = Vm Sin(ωt +240°) & B = Vm Sin(ωt +120°)

Y = Vm Sin(ωt +60°) & B = VmSin(ωt +120°)

Y = Vm Sin(ωt +120°) & B = VmSin(ωt+240°)

Y = Vm Sin(ωt +240°) & B = Vm Sin(ωt +120°)

Y = Vm Sin(ωt +90°) & B = Vm Sin(ωt -90°)

What is the phase current in phase Y and in phase B out of R-Y-B when sudden short circuit to all three phases occurs at no load? It is given that after fault current in phase R is equal (Vm Sin ‚âà√¨‚àö¬¢t)$

Y = Vm Sin(‚âà√¨‚àö¬¢t +240¬¨¬®‚Äö√†√ª) & B = Vm Sin(‚âà√¨‚àö¬¢t +120¬¨¬®‚Äö√†√ª)

Y = Vm Sin(‚âà√¨‚àö¬¢t +60¬¨¬®‚Äö√†√ª) & B = VmSin(‚âà√¨‚àö¬¢t +120¬¨¬®‚Äö√†√ª)

Y = Vm Sin(‚âà√¨‚àö¬¢t +120¬¨¬®‚Äö√†√ª) & B = VmSin(‚âà√¨‚àö¬¢t+240¬¨¬®‚Äö√†√ª)

Y = Vm Sin(‚âà√¨‚àö¬¢t +240¬¨¬®‚Äö√†√ª) & B = Vm Sin(‚âà√¨‚àö¬¢t +120¬¨¬®‚Äö√†√ª)

Y = Vm Sin(‚âà√¨‚àö¬¢t +90¬¨¬®‚Äö√†√ª) & B = Vm Sin(‚âà√¨‚àö¬¢t -90¬¨¬®‚Äö√†√ª)

When all three phases of a synchronous generator on no load are suddenly short circuited then symmetry of the short circuit current depends on which of the following?

Instantaneous Voltage at which fault occurs

14 + Mcqs in Short Circuit Synchronous Machine No Load in Power Systems Page 1 McqOptions

1.	Steady state direct axis reactance is greater than subtransient direct axis reactance and transient direct axis reactance.
A.	True
B.	False
Answer» B. False

Discussion

2.	Which of the following reactance is eliminated first in synchronous generator just after the symmetrical fault?
A.	Leakage reactance
B.	Damper winding reactance
C.	Armature winding reactance
D.	Field winding reactance
Answer» C. Armature winding reactance

Discussion

3.	If Xl is leakage reactance, Xf is reactance due to field winding, Xdw is reactance due to damper winding and Xa is armature winding reactance then reactance of synchronous generator in subtransient state is due to which of the following?
A.	Xl ,Xdw and Xa
B.	Xl and Xa
C.	Xl , Xf ,Xdw and Xa
D.	Xl and Xdw
Answer» D. Xl and Xdw

Discussion

4.	What is the phase current in phase Y and in phase B out of R-Y-B when sudden short circuit to all three phases occurs at no load? It is given that after fault current in phase R is equal (Vm Sin ωt)
A.	Y = Vm Sin(ωt +60°) & B = VmSin(ωt +120°)
B.	Y = Vm Sin(ωt +120°) & B = VmSin(ωt+240°)
C.	Y = Vm Sin(ωt +240°) & B = Vm Sin(ωt +120°)
D.	Y = Vm Sin(ωt +90°) & B = Vm Sin(ωt -90°)
Answer» C. Y = Vm Sin(ωt +240°) & B = Vm Sin(ωt +120°)

Discussion

5.	In a synchronous generator for how much time transient period of symmetrical short circuit current lasts?
A.	For 200 Cycles
B.	For 500 Cycles
C.	For 30 Cycles
D.	For 2 Cycles
Answer» D. For 2 Cycles

Discussion

6.	WHICH_OF_THE_FOLLOWING_REACTANCE_IS_ELIMINATED_FIRST_IN_SYNCHRONOUS_GENERATOR_JUST_AFTER_THE_SYMMETRICAL_FAULT??$
A.	Leakage reactance
B.	Damper winding reactance
C.	Armature winding reactance
D.	Field winding reactance
Answer» C. Armature winding reactance

Discussion

7.	Steady_state_direct_axis_reactance_is_greater_than_subtransient_direct_axis_reactance_and_transient_direct_axis_reactance.$
A.	True
B.	False
Answer» B. False

Discussion

8.	If X_l is leakage reactance, X_f is reactance due to field winding, X_dw is reactance due to damper winding and X_a is armature winding reactance then reactance of synchronous generator in subtransient state is due to which of the following?
A.	X<sub>l</sub> ,X<sub>dw</sub> and X<sub>a</sub>
B.	X<sub>l</sub> and X<sub>a</sub>
C.	X<sub>l</sub> , X<sub>f</sub> ,X<sub>dw</sub> and X<sub>a</sub>
D.	X<sub>l</sub> and X<sub>dw</sub>
Answer» D. X<sub>l</sub> and X<sub>dw</sub>

Discussion

9.	In case of synchronous generator the reactants is constant.
A.	True
B.	False
Answer» C.

Discussion

10.	What is the phase current in phase Y and in phase B out of R-Y-B when sudden short circuit to all three phases occurs at no load? It is given that after fault current in phase R is equal (Vm Sin ‚âà√¨‚àö¬¢t)$
A.	Y = V<sub>m</sub> Sin(‚âà√¨‚àö¬¢t +60¬¨¬®‚Äö√†√ª) & B = V<sub>m</sub>Sin(‚âà√¨‚àö¬¢t +120¬¨¬®‚Äö√†√ª)
B.	Y = V<sub>m</sub> Sin(‚âà√¨‚àö¬¢t +120¬¨¬®‚Äö√†√ª) & B = V<sub>m</sub>Sin(‚âà√¨‚àö¬¢t+240¬¨¬®‚Äö√†√ª)
C.	Y = V<sub>m</sub> Sin(‚âà√¨‚àö¬¢t +240¬¨¬®‚Äö√†√ª) & B = V<sub>m</sub> Sin(‚âà√¨‚àö¬¢t +120¬¨¬®‚Äö√†√ª)
D.	Y = V<sub>m</sub> Sin(‚âà√¨‚àö¬¢t +90¬¨¬®‚Äö√†√ª) & B = V<sub>m</sub> Sin(‚âà√¨‚àö¬¢t -90¬¨¬®‚Äö√†√ª)
Answer» C. Y = V<sub>m</sub> Sin(‚âà√¨‚àö¬¢t +240¬¨¬®‚Äö√†√ª) & B = V<sub>m</sub> Sin(‚âà√¨‚àö¬¢t +120¬¨¬®‚Äö√†√ª)

Discussion

11.	After how many cycles in a synchronous generator symmetrical short circuit current reaches to its steady state value?
A.	After 200 Cycles
B.	After 500 Cycles
C.	After 30 Cycles
D.	After 2 Cycles
Answer» D. After 2 Cycles

Discussion

12.	In a synchronous generator for how much time subtransient period of symmetrical short circuit current lasts?
A.	For 200 Cycles
B.	For 500 Cycles
C.	For 30 Cycles
D.	For 2 Cycles
Answer» E.

Discussion

13.	When all three phases of a synchronous generator on no load are suddenly short circuited then symmetry of the short circuit current depends on which of the following?
A.	Position of fault
B.	Symmetry of fault
C.	Instantaneous Voltage at which fault occurs
D.	Resistance of armature winding
Answer» D. Resistance of armature winding

Discussion

14.	Transient in synchronous generator is similar to which of the following circuit?
A.	Parallel RLC circuit
B.	Series RLC circuit
C.	Series RL circuit
D.	Parallel RL circuit
Answer» D. Parallel RL circuit

Discussion

Explore topic-wise MCQs in Power Systems.

Steady state direct axis reactance is greater than subtransient direct axis reactance and transient direct axis reactance.

Which of the following reactance is eliminated first in synchronous generator just after the symmetrical fault?

If Xl is leakage reactance, Xf is reactance due to field winding, Xdw is reactance due to damper winding and Xa is armature winding reactance then reactance of synchronous generator in subtransient state is due to which of the following?

What is the phase current in phase Y and in phase B out of R-Y-B when sudden short circuit to all three phases occurs at no load? It is given that after fault current in phase R is equal (Vm Sin ωt)

In a synchronous generator for how much time transient period of symmetrical short circuit current lasts?

WHICH_OF_THE_FOLLOWING_REACTANCE_IS_ELIMINATED_FIRST_IN_SYNCHRONOUS_GENERATOR_JUST_AFTER_THE_SYMMETRICAL_FAULT??$

Steady_state_direct_axis_reactance_is_greater_than_subtransient_direct_axis_reactance_and_transient_direct_axis_reactance.$

If Xl is leakage reactance, Xf is reactance due to field winding, Xdw is reactance due to damper winding and Xa is armature winding reactance then reactance of synchronous generator in subtransient state is due to which of the following?

In case of synchronous generator the reactants is constant.

What is the phase current in phase Y and in phase B out of R-Y-B when sudden short circuit to all three phases occurs at no load? It is given that after fault current in phase R is equal (Vm Sin ‚âà√¨‚àö¬¢t)$

After how many cycles in a synchronous generator symmetrical short circuit current reaches to its steady state value?

In a synchronous generator for how much time subtransient period of symmetrical short circuit current lasts?

When all three phases of a synchronous generator on no load are suddenly short circuited then symmetry of the short circuit current depends on which of the following?

Transient in synchronous generator is similar to which of the following circuit?

If X_l is leakage reactance, X_f is reactance due to field winding, X_dw is reactance due to damper winding and X_a is armature winding reactance then reactance of synchronous generator in subtransient state is due to which of the following?