Basic Electrical and Electronics Engineering by S. K. Bhattacharya, R. S. Choubey, Anubhuti Khare | 9789332509429 | 9332509425

Electronics and Electrical

Basic Electrical and Electronics Engineering

201 SOLVED PROBLEMS

4 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: 4.2

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: 4.1

A 220 V, 50 kW dc shunt generator was run as a motor on no load at rated speed. The current drawn from the line was 8 A and the shunt field current was 2 A. The armature resistance of the machine is 0.1 Ω. Calculate the efficiency of the generator at full load. ...

Verified Answer:

Input power at no load = VI = 220 × 8 = 1760 W Iro...

Question: 3.27

Calculate the all-day efficiency of a 25 kVA distribution transformer whose loading pattern is as follows: 15 kW at 0.8 power factor for 6 hours 12 kW at 0.7 power factor for 6 hours 10 kW at 0.9 power factor for 8 hours Negligible load for 4 hours. The core loss is 500 W and full-load copper loss ...

Verified Answer:

Output of the transformer in 24 hours is calculate...

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: III.8

(a) Perform the following conversions. 1. 38F 16 to octal 2. 153 8 to binary 3. 456 10 to hexadecimal 4. 1001 0111 2 in to decimal (b) Draw the logic circuit for the following Boolean expression expressed in two forms. Also write the truth table. Y = AC + BC (i) Y = C(A + B) (ii) ...

Verified Answer:

(a) 1. Writing the binary equivalent of each hexdi...

Question: III.7

(a) Convert 573 8 to decimal and 368 10 to binary form. (b) Explain the working of a RS flip-flop. ...

Verified Answer:

(a)

573_{8}=5 \times 8^{2}+7 \times 8^{1}+3...

Question: III.6

(a) How does a dc motor work? Explain the functions of brushes and commutators by providing the constructional details of a dc motor. (b) A six pole, three-phase synchronous generator driven at 1000 rpm supplies power to an induction motor running at 1440 rpm on full load. Calculate the percentage ...

Verified Answer:

(a) Refer to Sections 7.1-7.2.2 on Pages 7.1-7.8. ...

Question: 16.2

Binary number is 11010. Convert this number into its decimal equivalent. ...

Verified Answer:

\begin{array}{llllll} 1 & 1 & 0 &am...

Question: 5.2

A circular iron ring of mean diameter 25 cm and cross-sectional area 9 cm² is wound with a coil of 100 turns and carries a current of 1.5 A. The relative permeability of iron is 2000. Calculate the amount of flux produced in the ring. ...

Verified Answer:

Mean length of flux path,

\ell=\pi \mathrm{...

Question: 2.30

Apply Norton’s theorem to determine the current flowing through the resistance of 6 Ω connected across the terminals. A and B. Also calculate the potential of point A. What will be the current through the 6 Ω resistor across AK. Solve this problem using Thevenin’s theorem also. ...

Verified Answer:

After removing the 6 Ω resistor across terminals A...

Question: 2.16

Applying KCL, determine current IS in the electric circuit to make V0 = 16 V in the network shown in Fig. 2.40. ...

Verified Answer:

Now applying Kirchhoff’s current law to nodes A an...