Andhra University BE/B.Tech Elements of Eletrical Engineering Previous Paper 2010
First question is compulsory.
Answer any FOUR from the remaining questions.
All questions carry equal marks.
1.(A) what happens to the flux in a magnetic circuit if the reluctance is increasing for a given MMF?give the reasonns for your answer.
(b) A coil of 1000 turns is linked by a flux of 20 mwb. if the flux is reversed in a time of 2m.sec; what is the avg e.m.f induced in the coil?
(c) Can Swinburne’s test be done on a D.C series motors ? if so how? if not, why?
(d) Differentiate between form factor and power factor in A.C circuits.
(e)Draw the approximate equivalence circuit of a single-phase transformer when secondary is reffered to primary.
(f)give the various power stages in a 3-phases induction motor.
(g) Define the term Regulation of an alternator can it be -ve? if not why?
2. (a) Bring out the analogy between electric and magnetic circuits.
(b)an iron ring of cross-sectional area of 10 cm2 is wound with a wire of 1500 turns has a saw cut of 2mm gap. calculate the magnetising current required to produce of flux of 20 mwb if maen length of the magnetic path 40 cm and relative permeability of400 neglect leakage flux.
3. (a)Explain self inductance and mutual inductance derive the expression for coefficient of coupling btn 2 coils interms of self inductances of the coils and the mutual inductances btn them.
(b)A straight conductor of length 40 cm moves perpendicular to its axis at a velocity of 50 meters per second in a uniform magnetic field of flux density 1.2 tesla. Evaluate the e.m.f induced in the conductor if yhe direction of the motion is (i)normal to the field (ii) parallel to the field
4. derive the e.m.f equation in a D.c generator with usual notation
5. (a)Derive the voltage and current relation ships of line and phase in a 3 phase star connected system.
(b) an R-L series circuit supplied with 100 volts 40 hz, is found to take 10amps and when supplied with 100 volts 200 hz it takes 2 amps determine the valyes of r and l of the circuit assuming sinsodial current.
6. Explain how do you determine d parameters of d equivalent circuit of a single phase transformer from S.C and O.C test results.
7. explain why is slip essential for 3 phase inductor operation what happens if the slip is zero? explain.
8.(a)show that there is no starting torque available with a synchronous motor. name the various methods of starting it.
(b) a 3 phase 10 pole alternator has a star connected winding with 90 slots and 10 conductors per slot. the flux per pole is 30 mwb sinusoidally distributed and the speed is 600 r.p.m find the phase and line e.m.f induced under open circuit conditionshttp://www.stepinau.com/2013/09/26/andhra-university-beb-tech-elements-of-eletrical-engineering-previous-paper-2010/IT 2.1 Previous PapersCSE,CSE Previous Papers,Elements of Eletrical Engineering Previous Papers,IT,IT Previous Papers