Engineering Answers

A voltage e=250sinωt+50sin(3ωt+pi/3)+20 sin(5ωt+(5pi/6)) is applied to a series Circuit of resistance 20Ω and an inductance of 0.05H. Take ω=314rad/s

3.1 Derive an expression for the current. (5)

Calculate the following:

3.2 The rms value of the current and voltage. (2)

3.3 The total power supplied. (2)

3.4 The power factor. (1)

It is well kmown that the voltage drop across a resistor follows Ohm's Law:

V = RI

where I'R is the voltage drop in V. R is the resistance in a and /is the current in A. Employ the experimental data given in Table-1 below:

I in A = 4.3, 6.5

VR in V= 18, 30.5

Table-1: Resistor Voltage Drop with Current

Estimate the current for a voltage of v Volt, where v=(i+7)-th prime number and i=2 and hence find the value of R. (i) Use lincar interpolation method (ii) Use quadratic interpolation method (iii) Use Divided difference interpolation method. Hence compare the results obtained these methods.

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A 1100 V ,50 Hz, delta connected induction motor has a star connected slip ring rotor with a phase transformation ratio of 3.8. The rotor resistance and standstill leakage reactance are 0.012 Ω/phase and 0.25 Ω/phase respectively. Neglecting the stator impedance and magnetising current determine the rotor current at 4 % slip with slip rings shorted

A 150 KW ,3000 v, 50 Hz, 6-pole-star-connected induction motor has a start connected slip-ring with a transformation ratio of 3.6 (stator/rotor). The rotor resistance is 0.2 Ω/phase and its per phase/leakage reactance is 14.7 Ω/phase. The stator impedance may be neglected. Find the starting current and starting torque at rated voltage with short circuited slip–ring.