Q. The output voltage of a single-phase full bridge voltage source inverter is controlled by unipolar PWM with one pulse per half cycle. For the fundamental rms component of output voltage to be 75% of DC voltage, the required pulse width in degrees (round off up to one decimal place) is Solution: The output voltage […]
Q. The total impedance of the secondary winding, leads, and burden of a 5 A CT is 0.01 Ω. If the fault current is 20 times the rated primary current of the CT, the VA output of the CT is Solution: Given that, impedance of secondary winding = 0.01 Ω Rated current = 5 A
Q. Five alternators each rated 5 MVA, 13.2 kV with 25% of reactance on its own base are connected in parallel to a busbar. The short-circuit level in MVA at the busbar is . Ans: 100 Solution: Reactance of each alternator = 0.25 As all the five alternators are connected in parallel, the equivalent reactance
Q. If 𝑓 = 2𝑥3 + 3𝑦2 + 4𝑧, the value of line integral ∫𝐶 grad𝑓 ∙ 𝑑𝐫 evaluated over contour C formed by the segments (-3, -3, 2)→(2, -3, 2) →(2, 6, 2) →(2, 6, -1) is Ans:
Q. A current controlled current source (CCCS) has an input impedance of 10 Ω and output impedance of 100 kΩ. When this CCCS is used in a negative feedback closed loop with a loop gain of 9, the closed loop output impedance is (A) 10 Ω (B) 100 Ω (C) 100 kΩ (D) 1000 kΩ
Q. Given, 𝑉𝑔𝑠 is the gate-source voltage, 𝑉𝑑𝑠 is the drain source voltage, and 𝑉𝑡ℎ is the threshold voltage of an enhancement type NMOS transistor, the conditions for transistor to be biased in saturation are (A) 𝑉𝑔𝑠 < 𝑉𝑡ℎ ; 𝑉𝑑𝑠 ≥ 𝑉𝑔𝑠 − 𝑉𝑡ℎ (B) 𝑉𝑔𝑠 > 𝑉𝑡ℎ ; 𝑉𝑑𝑠 ≥ 𝑉𝑔𝑠 − 𝑉𝑡ℎ
Q. The characteristic equation of a linear time-invariant (LTI) system is given by ∆(𝑠) = 𝑠4 + 3𝑠3 + 3𝑠2 + 𝑠 + 𝑘 = 0. The system is BIBO stable if Ans: Option (C) Solution:
The characteristic equation of a linear time-invariant (LTI) system is given by Read More »
Q. A three-phase synchronous motor draws 200 A from the line at unity power factor at rated load. Considering the same line voltage and load, the line current at a power factor of 0.5 leading is (A) 100 A (B) 200 A (C) 300 A (D) 400 A Ans: 400 A
Q. The parameter of an equivalent circuit of a three-phase induction motor affected by reducing the rms value of the supply voltage at the rated frequency is (A) rotor resistance (B) rotor leakage reactance (C) magnetizing reactance (D) stator resistance Ans: magnetizing reactance Solution: Magnetic reactance (Xm) is depends on airgap flux and the flux
Q. A six-pulse thyristor bridge rectifier is connected to a balanced three-phase, 50 Hz AC source. Assuming that the DC output current of the rectifier is constant, the lowest harmonic component in the AC input current is (A) 100 Hz (B) 150 Hz (C) 250 Hz (D) 300 Hz Ans: 250 Hz Solution: In a
