Basic Electrical and Electronics Engineering by S. K. Bhattacharya | 9789332501126 | 9332501122

Basic Electrical

Basic Electrical and Electronics Engineering

69 SOLVED PROBLEMS

204 SOLVED PROBLEMS

Question: 4.16

A 400 V, 50 Hz, three-phase induction motor is rotating at 960 rpm on full load. Calculate the following for the motor: Number of poles; full-load slip; frequency of rotor-induced EMF; speed of the rotor magnetic field with respect to the rotor. Also show that both the stator field and the rotor ...

Verified Answer:

f = 50 Hz P = 2, 4, 6, etc.

N_{s} = \frac{...

Question: 4.8

A four-pole dc generator has 1000 conductors. The flux per pole is 25 mWb. Calculate the EMF induced when the armature is lap connected and run at 1500 rpm. At what speed the generator must be driven to produce the same EMF with the armature winding wave connected? ...

Verified Answer:

Case I P = 4, Z = 1000,

Φ = 25 × 10^{−3} W...

Question: 3.25

A 10 kVA 440/220 V, 50 Hz single-phase transformer gave the following test results when both the following tests were conducted on the high-voltage side: Open circuit test : 440 V, 1.0 A, 100 W Short circuit test : 20 V, 22.7 A, 130 W. Using the test data, calculate the efficiency and voltage ...

Verified Answer:

Full-load current on the high-voltage side = [late...

Question: 4.7

A four-pole 220 V dc series motor has 240 slots in the armature and each slot has six conductors. The armature winding is wave connected. The flux per pole is 1.75 × 10^−2 Wb when the motor takes 80 A. The field resistance is 0.05 Ω and the armature resistance is 0.1 Ω. The iron and friction losses ...

Verified Answer:

In a series motor the armature winding and the fie...

Question: 4.2

A four-pole dc generator having wave wound armature winding has 51 slots, each slot containing 20 conductors. Calculate the voltage generated in the armature when driven at 1500 rpm. Assume flux per pole to be 0.5 mWb. ...

Verified Answer:

P = 4, A = 2 (because the armature winding is wa...

Question: 3.26

A 440/220 V single-phase transformer has percentage resistance drop and reactance drop of 1.2 per cent and 6 per cent, respectively. Calculate the voltage regulation of the transformer at 0.8 power factor lagging. ...

Verified Answer:

Percentage voltage regulation

=\frac{(I...

Question: 4.8

A three-phase, four-pole, 50 Hz induction motor rotates at a full-load speed of 1470 rpm. The EMF measured between the slip-ring terminals when the rotor is not rotating is 200 V. The rotor windings are star connected and has resistance and stand-still reactance per phase of 0.1 Ω and 1.0 Ω, ...

Verified Answer:

N_{r} = 1470

rpm

N_{s} = \fr...

Question: 4.2

A four-pole, three-phase induction motor is supplied with 400 V, 50 Hz supply. The rotor-circuit resistance is 2 Ω and standstill rotor-circuit reactance is 8 Ω. Calculate the speed at which maximum torque will be developed. ...

Verified Answer:

Given, f = 50 Hz, P = 4.

R_{2} = 2 Ω, X_{...

Question: 2.47

A delta-connected three-phase motor load is supplied from a 400 V, thee-phase, 50 Hz supply system. The line current drawn is 21 A. The input power is 11 kW. What will be the line current and power factor when the motor windings are delta connected? ...

Verified Answer:

Line voltage,

V_{L} = 400 V, V_{Ph} = V_{...

Question: 2.37

An inductor having a resistance of 4 Ω and an inductance of 20 mH are connected across a 230 V, 50 Hz supply. What value of capacitance should be connected in parallel to the inductor to produce a resonance condition? What will be the value of the resonant current? ...

Verified Answer:

Z_{L} = R + j ωL, ω = 2πf = 2 × 3.14 × 50...

Question: 3.10

In Fig. 3.35 is shown a parallel circuit, an inductance L and a parallel R connected across 200 V, 50 Hz ac supply. Calculate: (a) the current drawn from the supply; (b) apparent power; (c) real power; (d) reactive power. ...

Verified Answer:

Resistance of resistive branch, R = 40 Ω Inductive...

Question: 16.14

Draw the logic circuit for the Boolean expression expressed in two forms. Also write the truth table Y = A^¯ C^¯ + B C^¯ (i) and Y = C^¯ (A^¯ + B) (ii) ...

Verified Answer:

for form (i) for form (ii) The truth table for [la...

Question: 16.13

The truth table for three variable inputs and single output logic circuit is shown below. Note that for three inputs the combinations are 2³ = 8. Construct the logic circuit using AND and OR gates. A B C X 0 0 0 1 0 0 1 0 0 1 0 1 0 1 1 0 1 0 0 0 1 0 1 1 1 1 0 0 1 1 1 0 ...

Verified Answer:

From observing the truth table we find that output...

Question: 16.12

1For the logic circuit shown in Fig. 16.10, write the Boolean expression and construct the truth table. ...

Verified Answer:

The Boolean expression is developed from Fig. 16.1...

Question: 16.11

Write the Boolean expression and truth table for the logic gate circuit shown in Fig. 16.8. ...

Verified Answer:

The Boolean expression is developed as shown below...

Question: 16.10

Convert 0.65 into its binary fraction. ...

Verified Answer:

\begin{array}{llll} & & \text { Fra...

Question: 16.9

Convert decimal 0.8125 into its equivalent binary number. ...

Verified Answer:

\begin{array}{llll} & & \text { Fra...

Question: 16.8

Determine the binary equivalent of decimal number 10. ...

Verified Answer:

\begin{array}{llrr}&&&Reminder\...

Question: 16.7

Determine the binary equivalent of decimal number 17. ...

Verified Answer:

\begin{array}{llrr}&&&Reminder\...

Question: 16.6

Convert decimal 23 into its binary equivalent number. ...

Verified Answer:

\begin{array}{llrr}&&&Reminder\...