A ramp type A/D converter is shown in the figure given below. The clock generator has a frequency of 1 MHz and the ramp generator produce a ramp voltage that increases from 0 V to 1.25 V in 125 ms. If the input Vi= 0.9 V, then number of clock pulses counted into the resister will be
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Solution
As shown in the figure, when Vr becomes equal TO Vi the comparator output switches to low level or zero which stopes further clock pulses from toggling the counting circuit. Let t1 is the time when comparator is high or the time of counting
A 32 km long, 33 kV, 3-phase overhead sub-transmission line has its conductor ACSR 15 mm diameter speaced at the corner of an equilateral triangle of 1.5 m side. The inductance per phase of the system is __________.
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Solution
Equation x cos x+ 3 = 0 is required to be solved using Newton’s method with an initial guess x0= 3.Then, after one step of Newton- Rephs on method, estimate x1 of the solution will be given by
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Solution
A three-phase motor is drawing 20 kVA at 0.707 power-factor lagging from a 220 V source. A capacitor bank is added with the motor to raise the power factor to 0.90 lagging. What should be the kVAR rating of the capacitor bank ?
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Solution
For both the condition (before and after the capacitor bank is added), power triangle is shown below
Power angle after the bank is added
θ2= cos–10.9 =25.84°
Reactive power before the capacitor is added
Q1= 20 ´ sin 45° = 14.14 kVAR
Reactive power after the capacitor is added
Q2 = 14.14 tan 25.84° = 6.85 kVAR
Required rating of capacitor bank
QC= Q1– Q2= 14.14– 6.85 = 7.29 kVAR
A 115 V, 60 Hz, 4-pole, single-phase induction motor is rotating in the clockwise direction at a speed of 1710 rpm. If the rotor resistance at standstill is 12.5 Ω, then the effective rotor resistance in forward branch will be
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Solution
The Laplace transform of x(t) is X(s) = \(e^{-2s}\frac{6s^{2}+s}{s^{2}+2s-2}\) The initial value of x(t) is__________.
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Solution
In the following circuit the RL will absorb maximum power if RL is equal to
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Solution
The equivalent inductance Leq is
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Solution
A dc circuit can be represented by an internal voltage source of 50 V with an output resistance of 100 kΩ. In order to achieve accuracy better than 99% for voltage measurement across its terminals, the voltage measuring device should have a resistance of atleast _____ MΩ.
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Solution
10 MΩ
In the measurement of power on balanced load by two Wattmeter method in a 3-phase circuit, the readings of the Wattmeters are 3 kW and 1 kW respectively, the latter being obtained after reversing the connections to the current coil. The power factor of the load is _____.
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Solution