Jawaharlal Nehru Technological University Hyderabad B.Tech II ELECTRICAL SYSTEMS Previous Question Paper (November/December - 2017 - R13)

State Kirchhoff’s Laws.

State Maximum Power Transfer theorem.

Define reactive and apparent power.

What is series resonance and explain?

Define EMF and Reluctance.

List the differences between core type shell type transformers.

Draw the load characteristics of series and compound generators.

Explain about methods of compensating Armature reaction.

Explain the draw backs of low power factor.

What is the necessity of a starter for starting DC motor?

Write the nodal equations and find the voltage across the 2Ω resistor for the network shown in figure 1.

Find the total resistance of the network shown in figure 2.

State and explain Reciprocity theorem with an example.

For the network of Figure 3 shown, find the value of R for maximum power and determine the maximum power delivered to R?

A coil consists of a resistance of 100 Ω and an inductance of 200 mH. If an alternating voltage, v, given by v=200 sin 500t volts is applied across the coil, calculate (i) the circuit impedance, (ii) the current flowing, (iii) the p.d. across the resistance, (iv) the p.d. across the inductance and (v) the phase angle between voltage and current.

A coil of inductance 0.20 H and resistance 60 Ω is connected in parallel with a 20 μF capacitor across a 20 V, variable frequency supply. Calculate the resonant frequency.

A circuit consisting of a resistor in series with a capacitor takes 100 watts at a power factor of 0.5 from a 100V, 60 Hz supply. Find (i) the current flowing, (ii) the phase angle, (iii) the resistance, (iv) the impedance, and (v) the capacitance.

What is parallel resonance? Derive a formula for resonant frequency fr in terms of L and C?

Derive the EMF equation of the single phase transformer.

A transformer takes a current of 0.8A when its primary is connected to a 240 volt, 50 Hz supply, the secondary being on open circuit. If the power absorbed is 72 watts, determine (i) the iron loss current, (ii) the power factor on no-load, and (iii) the magnetising current.

List the differences between core type and shell type transformer.

A 500 kVA transformer has a full load copper loss of 4kW and an iron loss of 2.5kW. Determine (i) the output kVA at which the efficiency of the transformer is a maximum, and (ii) the maximum efficiency, assuming the power factor of the load is 0.75.

Explain about demagnetizing Ampere turn per pole and Cross magnetizing Ampere Turn per pole.

Explain the classification of dc generators based on their excitation.

Derive the torque equation of DC Motor.

A 500V shunt motor takes a total current of 100A and runs at 1200 rev/min. If the shunt field resistance is 50 Ω, the armature resistance is 0.25 Ω and the iron, friction and windage losses amount to 2kW, determine the overall efficiency of the motor.

Explain the principle of double field revolving theory concept and hence draw the equivalent circuit of the single phase induction motor.

Define power factor? What are the causes for low power factor? List the disadvantages of low power factor.

Explain the working principle of three phase induction motor.

Draw and Explain the equivalent circuit of single phase induction motor.