Cochin University of Science and Techology (CUST) 2007 B.Tech Electronics and Communications Engineering Electrical Engineering - Question Paper
Electrical Engineering
BIS -II - (S) - 07 - 066
B, Tech Degree II Semester (Supplementary) Examination January 2007
rr/CS/EC 204 ELECTRICAL ENGINEERING H (OldScheme - 1995 Admissions)
Time r 3 Hours Maximum Marks : (OO
(AU questions cany KOUAh rnarks)
I, (a) Derive the EMF equation of a DC generator.
(b) Why is the starting current very high m DC motors? How does the 8Outer control it to a lAfe value?
OR
(I. (a) With ocat diagram explain Svrinburn's test on a DC routor.
(b) A 200 V DC shunt motor takes 4 A at ruled vofinge on no load. Armature and field resistances are 0.5 Q ind250fi respectively. Calculate the efficiency of the motor for a load of 40 A.
III. (a) Give the relation between' speed and frequency of an alternator. Find the omnberof
poles of an alternator running at 1500 rpm when ibe frequency Is 50 c/s.
(b) Explain the wurXicg ofasyftchrouous notor.
OR
IV. (a) Describe tho EMFmethodoffinding regulatkuiin altenwors.
(b) A3 - phase tar connected 1600 KVA, 13.5 KV, 50 Hz alternator h*A an effective armature resistance of 1.5 Ohm and synchronous reactance of 20 Ohms per phase. Estimate the percentage full load voltage regulation of the alternator at power Actors
0.B lag and 0.8 lead.
V. (a) Explsiothetanjue-slip characteristics c>f a 3 - phase kductionmoior. (b) A6-poleS0H7. * - phase induction nwtornins at 940 rpm when the shaft lorque is 200 N -in and the fHctiona] torque is 3 N - m and the aator losses is 1500 W. Calculate - (i) % slip (ii) rotor copper losses and (iit) efficiency.
OR
VI. (a) Explain the working of single phae induction motor using double field revolving theory, (b) Explain the shaded pole principle in mdnction motor.
VII. Explain in detail, the construction and operating principle of a permanent magnet moving coil ammeter.
OR
VTII. (a) Explain the working principle of eiecffodynamoraeter type wattmeter. (b) Explain various methods far extension of range of moving coil ammeters.
IX. (a) State and explain the laws of illumination.
fb) Explain with a aeat sketch the working of a circuit breaker
OR
X. Write short notes on: (I) Sodium Vapour Lamp (ii) Use of choke and starter in Fluorescent lamps
(iii) Under ground cable systems.
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| Earning: Approval pending. |
