8/14/2019 Nr210303 Electrical Engineering Set1

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8/14/2019 Nr210303 Electrical Engineering Set1

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Code No: NR210303 NR

i. Peak value of flux density in the core.

ii. Voltage induced in the secondary winding.

iii. Transformation ratio.

iv. EMF induced per turn in both the windings. [8]

6. (a) What is meant by slip in an induction motor? Develop an expression for thefrequency of rotor currents in it. [6]

(b) A 6-pole, 50 Hz, 3 -phase induction motor running on full-load with slip de-velops a torque of 160 N-M at its pulley rim. The friction and wind age lossesare 210 w and the stator copper and iron losses equal 1640 w calculate

i. Rotor output

ii. Rotor copper loss, and

iii. Efficiency at Full load. [10]

7. (a) Define % regulation and how do you find regulation of an alternator experi-

mentally. [8]

(b) A 3-phase, 4 pole star connected turbo alternator has a cylindrical rotor.Thereactance and resistance per phase of winding is 2.5 Ohms and 0.15 Ohms.The alternator has terminal potential difference of 6600V When delivering acurrent of 250 Amps. Calculate

i. The generated EMF at 0.6 PF lagging.

ii. The regulation at 0.6 PF lagging. [8]

8. (a) Sketch and describe the construction of a moving coil ammeter and give theprinciple of operation. [8]

(b) A moving coil instrument gives full scale deflection with 15mA and has aresistance of 5. Calculate the resistance of the necessary components inorder that the instrument may be used as

i. a 2A - Ammeter

ii. a 100V voltmeter. [8]

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