Basic Electrical Engineering by S. K. Sahdev | 9789332578739 | 9332578737

Basic Electrical

Basic Electrical Engineering

154 SOLVED PROBLEMS

Question: 10.4

The design requirements of an 11000/415 V, 50 Hz single-phase core type transformer are approximate emf/turn 15 V, maximum flux density 1.5 T. Find suitable number of primary and secondary turns and net cross-sectional area of core. ...

Verified Answer:

Here,

\quad\quad\quad E_{1} = 11000 V ; ...

Question: 10.5

A single phase 50 Hz core-type transformer has rectangular cores 30 × 20 cm and the maximum allowable density is 1.05 Wb/sq. m. Find the number of turns per limb on the high- and low-voltage sides for a voltage ratio of 3300/200 V. Take iron factor as 0.93. ...

Verified Answer:

Gross cross-sectional area = 30 × 20 = 600 cm² [la...

Question: 10.3

A 25 kVA transformer has 500 turns on the primary and 40 turns on the secondary winding. The primary is connected to 3000 V, 50 Hz mains, calculate (i) primary and secondary currents at full load, (ii) the secondary emf, and (iii) the maximum flux in the core. Neglect magnetic leakage, resistance ...

Verified Answer:

(i) At full load,

\quad\quad\quad I_{1} = ...

Question: 10.2

A power transformer has 1000 primary turns and 100 secondary turns. The cross-sectional area of the core is 6 sq cm and the maximum flux density while in operation is 10,000 Gauss. Calculate turns per volt for the primary and secondary windings. ...

Verified Answer:

Here,

N_{1} = 1000 ; N_{2} = 100 ; A_...

Question: 10.1

The emf per turn for a single-phase 2310/220 V, 50 Hz transformer is approximately 13 volt. Calculate the number of primary and secondary turns. ...

Verified Answer:

Here ,

\frac{E_{1}}{N_{1}} = \frac{E_{2}}...

Question: 9.10

A 6-pole, lap-wound DC motor takes 340 A when the speed is 400 rpm. The flux per pole is 0.05 Wb and the armature has 864 turns. Neglecting mechanical losses, calculate the BHP of the motor. ...

Verified Answer:

Here, P = 6; A = P = 6 (lap wound);

I_{L}[...

Question: 9.9

A 4-pole DC motor has a wave-wound armature with 594 conductors. The armature current is 40 A and flux per pole is 7.5 mWb. Calculate H.P. of the motor when running at 1,440 rpm. ...

Verified Answer:

Torque developed,

T = \frac{P Z \varphi I_...

Question: 9.8

The induced emf in a DC machine is 200 V at a speed of 1,200 rpm. Calculate the electromagnetic torque developed at an armature current of 15 A. ...

Verified Answer:

Here,

E_{b}

= 200 V; N = 1,200 rp...

Question: 9.7

A 50 H.P., 400 V, 4-pole, 1,000 rpm, DC motor has flux per pole equal to 0.027 Wb. The armature having 1,600 conductors is wave connected. Calculate the gross torque when the motor takes 70 A. ...

Verified Answer:

Torque developed,

T = \frac{P \phi Z I_{a...

Question: 9.6

A wave-wound armature of an 8-pole generator has 51 slots. Each slot contains 16 conductors. The voltage required to be generated is 300 V. What would be the speed of coupled prime mover if flux per pole is 0.05 Wb? If the armature is rewound as lap-wound machine and run by same prime mover, what ...

Verified Answer:

Here, P = 8; Φ = 0.05 Wb; number of slots = 51; co...