University of Mumbai 2008-8th Sem B.E Electrical and Electronics Engineering Principals of Electrical Design Old - Question Paper
Principals of Electrical Design Old Course Sem VIII May 2008
I r I i> >ti Of-
Con. 3068-08. (OLD COURSE) CO-3679
( 3 Hours) [Total Marks : 100
N. B. : (1) Attempt five questions, Q. No. 1 is compulsory. t . *}
(2) Figures to the right indicate full marks.
(3) Group the answers for each question.
(4) Assume suitable data wherever required. n
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1. Attempt any four: 20
(a) What is the role of consevator and breather in case of a transformer ?
(b) Explain duty cycle for an electrical motor. How motor rating depends on duty cycle.
(c) What are the types of leakage reactances in 3 phase Induction motor ?
(d) What is harmonic torquo ? Stato two methods to redues harmonic torques ?
(e) Explain the significance of B. in estimating the magnetizing current in a 34
induction motor.
2. (a) Discuss different accessories and their functions used for transformer. 10 (b) Discuss in detail the different methods of cooling of a transformer. 10
3. (a) Explain the method of calculating the magnetising Ampere turns for a tapered tooth. 10
Discuss, how to find out the Ampere turns of all the teeth under one pole.
(b) Derive an expression for reluctance offered by a parallel sided slot with single conductor 10 in a induction motor stator.
4. (a) Explain current distribution in the bars and end rings of a squirral cage induction 10
motor using neat diagram.
(b) What is overload capacity of an Induction motor ? Comment on the choice of various 10 design parameters on its overload capacity.
5. (a) Write in detial in different types of winding used in a transformer. 10
(b) A transformer is connected to 230 V/50 Hz input to deliver 50 V/3A output. If turns 10
per volts is 4, flux density is 1 -2 Wb/m2 for square cross section and current density is 2*2 A/mm?, find number of primary and cocondary turns, window space required and the window dimensions for a single phase transformer.
6. (a) Discuss in detail the mechanical forces developed in case of a transformer. 10
(b) Derive aid discuss the dispersion coefficient of a 3 phase induction motor in terms 10
of length air gap, number of poles and stator bore diameter.
7. Write short notes on any three 20
(a) Different types of insulation used in transformer
(b) Construction of core of a transformer using CRGO steel
(c) Different types of coils used and their applications in a transformer
(d) Prove the exponential low between time and temperature rise at a constant load for electrical equipment
(e) Find the expression for maximum power factor in terms of dispersion coefficient for a 3 phase induction motor.
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