DO - DOT - Self Learning Assessment

1. In a balanced 3-phase system,
A) Only negative sequence current is zero
B) Only zero sequence current is zero
C) Both negative and zero sequence current are zero
D) none of the above
2. On the occurrence of an unsymmetrical fault, the sequence component which is always greater than the negative sequence component is
A) zero sequence component
B) positive sequence component
C) both [a) + b)]
D) none of the above
3. The fault on a power system that gives symmetrical fault current is
A) line to line fault
B) three-phase short-circuit fault
C) single line to ground fault
D) none of the above
4. The positive sequence impedance of a feeder is 3 Ώ. It’s negative sequence impedance will be:
A) 3 Ώ
B) 9 Ώ
C) 6 Ώ
D) 1 Ώ
5. In a 3-phase, 4 wire unbalanced system, the current in the neutral wire is 12 A. The zero sequence current in each phase is
A) 12 A
B) 6 A
C) 24 A
D) 4 A
6. In a 3-phase, 4 wire balanced system, the phase sequence is RYB. If the voltage of R phase is. 230 < 0° V, then for Y phase
A) 230 < 0 V
B) 230 < 60° V
C) 230 < 90°V
D) 230 < 120° V
7. If the height of transmission towers is increased, which of the following parameters is likely to change?
A) Resistance
B) Inductance
C) Capacitance
D) None of the above
8. A module in a solar panel refers to
A) Series arrangement of solar cells
B) Parallel arrangement of solar cells
C) Series and parallel arrangement of solar cells
D) None of the above
9. The rotor current in a three phase induction motor is …………….. slip.
A) inversely proportional to
B) directly proportional to
C) independent of
D) none of the above
10. The starting torque of a 3 phase induction motor is ………… supply voltage.
A) independent of
B) directly proportional to
C) directly proportional to square of
D) none of the above
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