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F2108 Pages:

Roy

A coil consists of 750 turns and a current of 10 A in the coil produces a magnetic
flux of 1.2 mwb. Calculate the inductance of the coil. If the current in the coil is
reversed in 0.01 seconds,find the average emf induced in the coil.
Derive the expressions for self-inductance and mutual-inductance.
Derive the expressions for RMS value, Average value and Form factor of a
sinusoidal waveform.
Draw the phasor diagram for a series RL circuit and give the expression for
Impedance.
A balanced Y connected load of 8+j6 Q per phase is connected to a 3 phase, 400
V supply. Find the line current, Power factor, Active Power, Apparent power and
Reactive Power.
How power is measured in a 3-phase system using 2 wattmeters? Give the
Connection diagram, Phasor diagram and necessary expressions.
With the help of a neat schematic diagram explain the working of a Hydroelectric
Power Plant.

MODULE 5

Answer any one full question
A 4 pole,250 V DC series motor has a wave connected armature with 1254
conductors. The flux per pole is 22 mwb when the motor is taking 50 A.
Armature resistance is 0.2 ohms and series field resistance 0.2 ohms. Calculate
the speed.
Give the classification of DC generators with necessary diagrams
OR
In a 25 KVA, 3300/230V single phase transformer, the iron and full load Copper
losses are 350 and 400 watts respectively. Calculate the efficiency at half full
load,0.8 pf.
MODULE 6
Answer any one full question
Why a single-phase induction motor is not self-starting? Give a detailed
description of any two methods for starting asingle-phase induction motor.
OR
Describe briefly the principle of operation of a 3-phase induction motor.
Define Synchronous speed and slip with respect to an Induction motor
A 3-phase Induction motor has 6 poles. It is connected to 3 phase, 400Volts, 50

Hz supply. The motor is operating at 5% slip. What is the speed of the motor.
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