# Dr. A.P.J. Abdul Kalam University BE IV SEM (EX) Electrical Machine-I [EX-225T] June 2021 Question Paper

Dr. A.P.J. Abdul Kalam University

Bachelor of Engineering

Fourth Semester Main Examination, June-2021

Electrical Machine-I [EX-225T]

Branch- EX

Time: 3:00 Hrs Max Marks 70

Note : Attempt any five questions. All question carry equal marks.

Q.1 (a) Define efficiency and derive the condition for max. Efficiency.

(b) Explain different type of losses in transformer. How can they be

minimized?

Q.2 (a) Why is the power factor of a single-phase induction motor low? Write the

applications of 1-phase induction motor.

(b) Explain the working principle of Single phase transformer & derive e.m.f.

equations.

Q.3 (a) Draw the equivalent circuit and phasor diagram for lagging and

(b)Draw and explain Scott connection of 3-phase transformer. Write Application

of Scott connection.

Q.4 (a) Explain the parallel operation of transformer. Describe conservator and

breather.

(b) Explain different types of connection used in 3 phase transformer?

Q.5 (a) How to make single phase induction motor self starting.

(b) Describe the construction, working principle of 3-phase induction motor with

the help of neat diagram.

Q.6 (a) Draw the torque-speed characteristics of three phase induction motor(with

effect of increasing resistance).

(b) What is Slip? Comparison of slip ring and squirrel cage motors.

Q.7 (a) How an Induction Motor is started? Why the Starter is used?

(b)Write a short note on Crawling and Cogging or Magnetic locking on

induction machine.

Q.8 Write a short note on :– a) Polarity test b) Load test (sumpner’s or back to

back test)

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