EE2251 Electrical Machines - I - Part B Important Questions (Unit I & II)

UNIT-I

1. Explain the methods of analyzing the magnetic circuits

2. Explain the two types of magnetic circuits with neat diagram

3. Explain in detail about electromagnetic induction

4. Draw the typical B-H curve and hysteresis loop and explain its concepts

5. Explain the meaning of self induced emf, mutually induced emf, statically induced emf, dynamically induced emf and give practical examples

6. Distuingusih between statically induced emf and dynamically induced emf

7. Prove that M=k√L1L2

8. Explain about magnetization curve for Ferro magnetic material

9. Explain in detail about hysteresis loss and eddy current loss in detail

10. Explain various types’ core loss on detail

UNIT-II

1. Explain the construction of a transformer.

2. a. Derive the emf equation of a transformer.(8)

b. Develop an approximate equivalent circuit for a two winding transformer. (8)

3. A 100 KVA 1100/200v single phase transformer has the following parameters.R1 = 1Ω, X1= 3Ω , R2=0.04Ω, X2=0.012Ω . Find the equivalent resistance and leakage reactance as referred to High Voltage winding.

4. a. Discuss about the working principle of a transformer. (8)

b. Draw the phasor diagram & explain the operation of a practical transformer on load. (8)

5. Draw the equivalent circuit of a single phase 1100/220 V transformer on which the Following results were obtained.

i . 1100V, 0.5A, 55W on primary, secondary being open circuited. (8)

ii. 10v, 80A, 400W on low voltage side, high voltage being short circuited. (8)

Calculate the voltage regulation and efficiency of the above transformer when secondary supply is 100A at 0.8 pf lagging.