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GATE’22 EE: Daily Practices Quiz
GATE’22 EE: Daily Practices Quiz 20-Sep-2021
Each question carries 2 marks
Negative marking: 2/3 mark
Total Questions: 05
Total marks: 10
Time: 12 min.
Q1. An overhead transmission lines the effect of capacitance can be neglected when the length of line is less than
(a) 200 km
(b) 160 km
(c) 100 km
(d) 80 km
Q2. A 3- ϕtransmission line uses 1.24 cm diameter conductor and these are placed at corners as shown below of 2 m. The inductance/phase is
(a) 12×10^(-7) H
(b) 8.4 × 10^(-7) H
(c) 7.6 × 10^(-6) H
(d) 12.5 × 10^(-6) H
Q3. The rotor bar current in a three-phase squirrel cage induction motor is 100 Amp. The rotor resistance is 0.05 Ohm/phase. At a slip of 5% the air gap power is
(a) 5 kW
(b) 10 kW
(c) 30 kW
(d) 60 kW
SOLUTIONS
S1. Ans.(d)
Sol.
Type of Transmission | If f = 50 Hz then, length is | Effect of capacitance |
Short line | L < 80 km | Neglected |
Medium line | 80 km < L < 240 km | The capacitor is lumped and constant |
Long line | L > 240 km | Capacitance is uniformly distributed |
S3. Ans.(c)
Sol. Given, Rotor current (I_2 ) = 100 A
Rotor resistance (R_2 ) = 0.05 Ω\/Phase
Slip = 5 % = 0.05 pu
Air gap power (Pg.) =?
Copper Loss (P_cu ) = 3 (I_2 )^2 R_2
= 3 × (100) ² × 0.05
= 3 × 10^4 × 0.05
= 1500 W
Air gap power of 3 – ϕ squirrel cage induction motor is given by-
P_g=P_cu/S=1500/0.05
= 3 × 10^4
= 30 kW