QUESTIONS CARRY TWO MARKS EACH.
The 6 V Zener diode shown in the figure below has zero Zener resistance and a knee current of 5mA. The minimum value of R so that voltage across it does not fall below 6 V is ______
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Solution
QUESTIONS CARRY TWO MARKS EACH.
A 3-phase IM is driving a constant torque load of 1 pu at 5% slip. It has a maximum torque of 2 pu at 10% slip. Torque-speed variation in stable zone is assumed to be linear. For the stable operation of the motor, the minimum p.u. supply voltage is approximately _______ .
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Solution
QUESTIONS CARRY TWO MARKS EACH.
A 3-phase alternator delivers power to a balanced 3-phase load of power factor 0.707 lagging. It is observed that the open-circuit emf phaser by 15°. Neglecting the effect of harmonics, the angle between the axis of the main-field mmf and the axis of armature mmf will be _______°.
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Solution
The angle between the axis of main field mmf and the axis of armature mmf will be =ψ=90°
where ψ = δ + φ = 15° + cos-1.707 = 60°
∴ Total angle = 60° + 90° = 150°
QUESTIONS CARRY TWO MARKS EACH.
A variable w is related to three other variables x, y and z as w= xy/z. The variables are measured with meters of accuracy± 0.5% reading, ± 1% of full scale value and ± 1.5% reading.The actual readings of the three meters are 80, 20 and 50 with 100 being the full scale value for all three. The maximum uncertainty in the measurement of w will be
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Solution
QUESTIONS CARRY TWO MARKS EACH.
A three-phase transformer having zero-sequence impedance of Z0 has the zero-sequence network as shown in the below figure. The connections of its windings are
QUESTIONS CARRY TWO MARKS EACH.
The principal information obtained from load flow studies in a power system are 1.magnitude and phase angle of the voltage at each bus 2.reactive and real power flows in each of the lines 3.total power loss in the network 4.transient stability limit of the system Select the correct answer using the codes given below:
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Solution
Slack bus is made to take the additional real and reactive power to supply transmission losses.
QUESTIONS CARRY TWO MARKS EACH.
The parameters of the transistor in the circuit shown below are β= 100 and VA= 100 V.
The small-signal voltage gain Av= v0/vs is
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Solution
QUESTIONS CARRY TWO MARKS EACH.
The reactance of a generator designated X” is given as 0.25pu based on the generator’s name plate rating of 18kV, 500 MVA. If base for calculations is changed to 20 kV,100 MVA, then generator reactance X” on new base will be ______
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Solution
QUESTIONS CARRY TWO MARKS EACH.
For the circuit shown in the figure below, the switch ‘K’was closed for a long time till steady state conditions reached. If at time t = 0, the switch ‘K’ is opened, then current through inductor will be
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Solution
QUESTIONS CARRY TWO MARKS EACH.
Initial contents of the 4-bit serial-in-parallel-out, right-shift-, shift-Register shown in the figure below is 0110.After three clock pulses are applied, contents of the Shift Register will be ______
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Solution
4 bit SIPO
Pulse 1 XOR (1, 0) = 1 1011
2 XOR (1, 1) = 0 0101
3 XOR (0, 1) = 1 1010
Contents will be 1010