Dr.A.P.J.Abdul Kalam University Old Question Papers

Bachelor of Engineering

Eighth Semester Main Examination, Aug-Sep 2020

Computer Aided Electrical Machine Design [EX-801]

Branch- EX

Time: 3:00 Hrs Max Marks 70

Note : 1. Attempt any five questions.

2. All question carry equal marks.

3. Answer should be precise & to be point only.

4. Assume suitable data if necessary & state them clearly.

Q.1 (a) Why computer aided design of rotating machines are complicated? Draw the flow chart for

the computer aided design of rotating machines.

(b) What are the various approaches in computer aided design? Explain with flow chart.

Q.2 (a) Explain specific electrical loading and specific magnetic loading.

(b) Write advantage and disadvantage of choosing high value of specific electrical loading and specific magnetic loading.

Q.3 (a) Derive the output equation of DC machine in terms of design constants.

(b) How the armature winding of DC machine is design?

Q.4 (a) Determine suitable values fori) External diameter of armature

ii) Core length

iii) Number of poles, for a 1000 KW, 500 Volts and 350 r.p.m D.C. generators.

Assume suitable values for electric and magnetic loading. Justify the values of diameter and

length of armature from the limiting value of peripheral speed and voltage between the adjacent

commuter segments respectively.

(b) Derive the output equation of a 3 phase transformer in terms of design constants.

Q.5 (a) Explain why power transformer is design to have maximum efficiency at or near full load

(b) Deduce an expression between volts per turn and K.V.A rating of a transformer.

Q.6 (a) Calculate the core and window area required for a 1000 KVA, 6600/400 volts 50 HZ, 3 phase

core type power transformer. Assume a flux density in the core of 1.38 tesla. A current density

of 2.35 A/mm2 and window space factor of 0.32.

(b) Derive the output equation of a 3 phase induction motor is terms of design constants.

Q.7 (a) Explain the factor affecting the 3 phase transformer is terms of design constants .

(b) Explain crawling and cogging phenomena.

Q.8 (a) Calculate the main dimensions for a 250 KVA, 6600/400 volts 50 HZ 3 phase delta/ star core

type oil immersed self cooled outdoor type power transformer. Assume suitable values for

various design constants and specific magnetic loading.

(b) Derive the output equation of a 3 phase synchronous machine in terms of design constants.

(c) Calculate the following design information’s for a 30 KW , 440 KW, 3-phase, 6 pole, 50 Hz

delta connected ,sq. cage induction motor,

a) i) Main dimensions of stator frame

ii) Number of turns per phase in stator winding

iii) Number of stator slots

iv) Number of conductors per slot

b) Assume suitable values for the missing data

(d) Calculate the stator core dimensions for a 10 MVA, 11 KV, 50 Hz,

3 phase, 2 pole turbo alternator , based on the following information:

i. Specific magnetic loading Bav=0.63 Tesla

ii. Specific electric loading, q=48000 amp.cond/m

iii. Limiting peripheral speed v=120 m/sec.

iv. Length of air gap lg=2.0 cm, Stator winding factor kw=0.955

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