141. Energy is stored in Flywheel in the form of __________
A. Kinetic energy
B. Electrical energy
C. Solar energy
D. Wind energy
Answer: A
Energy is stored in Flywheel in the form of kinetic energy. It stores rotational kinetic energy.
142. Calculate the coefficient of fluctuation of speed using the data: Vmax(Fluctuation) = 25 m/sec, Vmean = 12 m/sec.
A. 2.08
B. 2.16
C. 2.34
D. 2.74
Answer: A
The coefficient of fluctuation of speed is the ratio of the maximum fluctuation speed and mean speed.
C.F = Vmax(Fluctuation) ÷ Vmean = 25÷12 = 2.08.
143. Calculate the maximum fluctuation of speed using the data: Vmax = 23 m/sec, Vmin = 13 m/sec.
A. 12
B. 10
C. 14
D. 15
Answer: B
The maximum fluctuation of speed is the difference between the maximum speed and minimum speed. Maximum fluctuation of speed
= Vmax – Vmin = 23 – 13 = 10.
144. Calculate the Kinetic energy of the object of mass = 7 Kg moving in a straight line with a velocity of 12 m/s.
A. 504 J
B. 502 J
C. 503 J
D. 509 J
Answer: A
The Kinetic energy of the object of mass = 7 Kg moving in a straight line with a velocity of 12 m/s is
.5×m×v2 = .5×7×12×12 = 504 J.
145. Calculate the rotational kinetic energy of the object using the data: I = 5 Kg-m2, ω = 25 rad/sec.
A. 1.46 KJ
B. 1.56 KJ
C. 2.58 KJ
D. 3.15 KJ
Answer: B
The Kinetic energy of the object having a moment of inertia = 5 kg-m2 rotating with an angular velocity equal to 25 rad/sec is
.5×I×ω2 = .5×5×25×25 = 1.56 KJ.
146. Calculate the line voltage for 3-∅ 120° VSI if the value of DC supply is 96 V.
A. 68.25 V
B. 67.87 V
C. 66.25 V
D. 62.14 V
Answer: B
The line voltage for 3-∅ 120° VSI is
(VDC÷√2) = .707×96 = 67.87 V.
In 3-phase 120° VSI each phase conducts for 120° and only three switches from different phases conduct simultaneously.
147. Calculate the phase voltage for 3-∅ 120° VSI if the value of DC supply is 78 V.
A. 30.45 V
B. 15.18 V
C. 31.84 V
D. 48.15 V
Answer: C
The line voltage for 3-∅ 120° VSI is (VDC÷√6) = 31.84 V.
In 3-phase 120° VSI each phase conducts for 120° and only three switches from different phases conduct simultaneously.
148. Calculate the r.m.s value of thyristor current in 3-Φ Full-wave converter for the load current = 2 A and α = 59°.
A. 1.15 A
B. 2.55 A
C. 2.07 A
D. 2.89 A
Answer: A
The r.m.s value of thyristor current in a 3-Φ Full-wave converter is Io√1÷3. It is the r.m.s value of the thyristor current.
I(r.m.s) = Io√1÷3 = 1.15 A.
149. Calculate the average value of thyristor current is n 3-Φ Full-wave converter for the load current = 729 A and α = 3°.
A. 254 A
B. 285 A
C. 247 A
D. 243 A
Answer: D
The average value of thyristor current in a 3-Φ Full-wave converter is Io÷3. It is the average value of the thyristor current.
I(r.m.s) = Io÷3 = 243 A.
150. 1600 V rated 8 SCRs are connected in series. The operation voltage of the string is 4400. Calculate the string efficiency.
A. 34.37 %
B. 30.15 %
C. 38.48 %
D. 35.84 %
Answer: A
The string efficiency can be calculated using the formula
operation voltage ÷ (Number of SCRs×Rated voltage) = 4400÷(1600×8) = 34.37 %.
151. The use of the inductor in CSI is to make the source current constant.
A. True
B. False
Answer: A
The inductor in CSI is used to make the source current constant. The input current of CSI should be constant.
152. The output voltage of CSI depends upon the load.
A. True
B. False
Answer: A
The output voltage of CSI depends upon the load. The output current of CSI is fixed as the input source current is fixed.
153. Which one of the elements is used to make R load commutating?
A. Inductor
B. Capacitor
C. Resistor
D. Coil
Answer: B
The capacitor is used to make the R load commutating. It is used in parallel with the resistive load.
154. Calculate the minimum period for ASCI using the data: R = 12 kΩ, C = 45 μF.
A. 2.58 sec
B. 2.16 sec
C. 2.23 sec
D. 2.48 sec
Answer: B
The minimum time period for ASCI is a
4×R×C
= 4×12×45×.001 = 2.16 sec.
The total time is the sum of charging and discharging time.
155. Full form of ASCI is ___________
A. Auto sequential commutated inverter
B. Auto starter commutated inverter
C. Auto sequential current inverter
D. Auto sequential current inserter
Answer: A
ASCI stands for Auto sequential commutated inverter. No external forced commutation is required for ASCI. The capacitor itself works as a load-commutated inverter.
156. Calculate the maximum frequency for ASCI using the data: R = 15 kΩ, C = 5 μF.
A. 3.51 Hz
B. 3.69 Hz
C. 3.33 Hz
D. 3.98 Hz
Answer: C
The maximum frequency for ASCI is
1÷(4×R×C) = 1÷(4×15×5×.001) = 3.33 Hz.
The total frequency is the sum of charging and discharging frequency.
157. The output current waveform for R load in CSI is ___________
A. Square
B. Triangular
C. Constant
D. Vertical
Answer: A
The output current of CSI for R load is square in nature. The amplitude of the output current varies from I to -I.
158. T.H.D value for CSI is ________
A. 48.43 %
B. 41.15 %
C. 39.15 %
D. 46.48 %
Answer: A
T.H.D value for VSI is 48.43 %. Triple harmonics are present in CSI due to which harmonic content increases.
159. What is the distortion factor value in CSI?
A. .85
B. .90
C. .95
D. .88
Answer: B
The distortion value in CSI is .90. The r.m.s value of the fundamental current is 2√2I÷π and the r.m.s value of the output current is I. The distortion factor is (2√2I÷π)÷I = .90.
160. Number of switches turned on in CSI at a single time is __________
A. 2
B. 4
C. 5
D. 3
Answer: A
In CSI two switches conduct at a single time. The common switch used in CSI is thyristor. Thyristors are unidirectional, and bipolar in nature.
