LIVE Course for free

Rated by 1 million+ students
Get app now
0 votes
95 views
in General by (59.9k points)
closed by
A DC motor takes an armature current of 100 A at 440 V. The armature circuit resistance is 0.3 Ω. The machine has 6 poles and armature is lap-connected with 822 conductors, the flux per pole is 0.05 wb. Calculate the speed.
1. 598.5 rpm
2. 610 rpm
3. 698 rpm
4. 710 rpm

1 Answer

0 votes
by (110k points)
selected by
 
Best answer
Correct Answer - Option 1 : 598.5 rpm

Concept:

The EMF equation of a DC Machine is

\({E_b} = \frac{{NPϕ Z}}{{60A}}\)

In a dc motor, back emf is

Eb = V – IaRa

Where,

N is the speed in rpm

ϕ is the flux per pole

P is the number of poles

Z is the number of conductors

V is the terminal voltage

Ia is the armature current

Ra is the armature resistance

Calculation:

Given V = 440 V

Ia = 100 A

Ra = 0.3 Ω

P = 6

A = P = 6 (LAP winding)

Z = 822

ϕ = 0.05 wb 

Eb = V – IaRa

Eb = 440 - 100 × 0.3 = 410 V

\({E_b} = \frac{{NPϕ Z}}{{60A}}\Rightarrow N =\frac{E_b\times 60\times A}{Pϕ Z}\)

\(N = \frac{410 \times 60 \times6 }{6\times 0.05\times 822}=598.54\;rpm\)

∴ The speed is 598.5 rpm

Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ experts/mentors/students.

Categories

...