Course file

1. ELECTRICAL ENGINEERING
DEPARTMENT OF ELECTRICAL & ELECTRONICS
ENGINEERING
COURSE MATERIAL
FOR
FOR II/IV B.Tech I Semester
[Common to Mech.Engg – Mechatronics and Mech.Engg – Production]
Dr. NARASIMHAM R.L.
VIGNAN INSTITUTE OF TECHNOLOGY & SCIENCE
VIGNAN HILLS, DESHMUKHI VILLAGE,
POCHAMPALLY (MANDAL)
NALGONDA (Dt.) – 508 284

2. ELECTRICAL ENGINEERING
II year B.Tech I Semester ME 2123
UNIT – I
Syllabus: SI Unit’s law, series and parallel circuits, Kirchhoff’s laws, Star-delta
transformation – magnetic circuits – force on a current carrying conductor –
electromagnetic induction, Faraday’s law, Lenz’s law – effects of hystersis & eddy
currents – self and mutual inductances.
This unit mainly focuses on SI UNITS, Fundamental aspects of Electrical
Engineering circuit theory and stresses on the following Objectives:
- The series and parallel circuits with the circuit elements i.e. Resistances,
inductors and Capacitors.
- Study of Kirchhoff’s laws & Star-delta transformation
- Basic concept of Magnetic circuits
- Study of force on a current carrying conductor
- Faraday’s laws of Electromagnetic Induction
- Effect of Hystersis & Eddy currents
- Self & Mutual Inductances
Lecture Plan
UNIT - I
 SI Unit’s law, series and parallel circuits
 Kirchhoff’s laws
 Star-delta transformation
 Magnetic circuits – force on a current carrying conductor 14 Periods
 Electromagnetic induction, Faraday’s law, Lenz’s law
 Effects of hystersis & eddy currents
 Self and mutual inductances.

3. UNIT – II
Syllabus: Generation of an alternating emf – average and r m s values of alternating
quantity – representation of alternating quantities by phasors – single phase circuits –
resonance – three phase balanced systems single and three phase power calculations.
This unit deals with Alternating current quantities relating to single phase circuits
including resonance and 3 phase Balanced circuits:
- Generation of Alternating currents; Average & Peak values of different wave forms;
Their relationships.
- Study of Phasor representations and single phase circuits
- Series and parallel resonance.
- Three phase Balanced systems
- Study of single –Phase and three-phase power calculations.
Lecture Plan:
 Generation of an alternating emf average and r m s
values of alternating quantity
 Representation of alternating quantities by
phasors single phase circuits
 Resonance – three phase balanced systems
 Single and three phase power calculations.
UNIT – III
Syllabus: Principle of operation of DC machines – emf equation – types of generators –
Magnetization and load characteristics of DC generators – types and characteristics of
DC motors – torque equation –DC motor starters (three point) – Efficiency calculation
and swimburne’s test – speed control.
This unit focuses on D.C. Motors and D.C. Generators including three point
starters.
- Principle of D.C.Machines and EMF equations.
- Types of generators, their magnetizations and load characteristics
- Types of D.C. Motors and their characteristics.
- Torque Equation of D.C. Motors
- Three-point starters
- Efficiency calculations
- Speed control of D.C. Machines and Swimburne’s Test
12 Periods

4. Lecture Plan:
 Principle of operation of DC machines
 emf equation – types of generators
 Magnetization and load characteristics of DC generators
 Types and characteristics of DC generators
 Types and characteristics of DC motors torque equation
 DC motor starters (three point) – Efficiency calculation
and swimburne’s test – speed control
UNIT – IV
Syllabus: Construction and principle of operation of single phase transformer – emf
equation O.C. & S.C. tests – efficiency and regulation - 3 Transformers, Transmission
and Distribution – principle and operation of three phase induction motors –types – slip
torque characteristics – Principle and operation of alternators – O.C. & S.C. tests –
regulations by synchronous impedance method.
This unit reflects the various aspects of A.C. Machines and their important
characteristics, regulation and efficiency.
- Construction & principle of single phase Transformer O.C. & S.C. Tests Calculations
of Efficiency & Regulation
- Three-Phase Transformers and its applications (Transmissions and Distribution)
- Three – Phase Induction Motor Principle, Slip – Torque characteristics
- Alternators – Principle, Study of O.C. & S.C. Tests Regulations by synchronous
Impedance method
-
Lecture Plan:
 Construction and principle of operation of single phase transformer
 emf equation O.C. & S.C. tests – efficiency and regulation
 3 Transformers, Transmission and Distribution
 Principle and operation of three phase induction motors –types 16 Periods
 Slip torque characteristics
 Principle and operation of alternators
 O.C. & S.C. tests – regulations by synchronous impedance method.
12 Periods

5. UNIT – V
Basic Principles of indicating Instruments – Moving coil and moving iron
instruments – Dynamometer type wattmeters – Induction types energy meter
Measurement of single and three phase power.
This unit mainly focuses on Electrical Measuring Instruments commonly used for
measurement applications and calibrations point of view.
- Types of Measuring Instruments
- M.C. & M.I. instruments
- Dynamometer Type W.M.
- Induction Type Energy Meter
- Measurement of single-Phase and Three-phase power calculations
Lecture Plan:
 Basic Principles of indicating Instruments
 Moving coil and moving iron instruments
 Dynamometer type wattmeters 10 Periods
 Induction types energy meter
 Measurement of single and three phase power.
Total No. of Teaching Periods - 64
TEXT BOOKS:
1. Electrical Engineering Fundamentals/DelToro.2nd
edition/Prentice Hall Publishers
2. Fundamental of Electrical Engineering/Ashfaq Husain. 2nd
edition/Dhanpat Raj & Co.
3. Theory and Problems of Basic Electrical Engineering/D.P.Kothari & I.J.Nagrath,
PHI Publishers, 1998.
4. Basic Electrical Engineering/ V.N.Mittle / TMH 1998
5. Electrical Technology/H.Cotton.7th
edition

6. UNIT – I QUIZ – I
1) The Basic electric quantities are
a) Charge & voltage b) Energy & Current
c) Charge & Energy d) Voltage & Current [ ]
2) Current is defined as
a) Rate of change of charge b) Product of charge & time
c) Rate of charge of flux d) Rate f charge of voltage [ ]
3) The difference of Potential between two points in a circuits
a) Voltage b) Current
c) Resistance d) Zero [ ]
4) A circuit element draws a constant current of 5A at a constant voltage of 10v. The
energy absorbed by it in one hour
a) 50 kwh b) 15kwh c) 0.5kwh d) 0.05kwh [ ]
5) The circuit element absorbs 500 watts of power with a current of 10A, its voltage is
a) 500v b) 450v c) 50v d) 510v [ ]
6) The voltage and current across a resistor are 5v, 2A respectively, The value of the
resistance and the power absorbed are
a) 2.5 & 10Watts b) 5 & 5W
c) 0.5 & 10W d) 2.5 & 5W [ ]
7) The resistance of wire is directly proportional to
a) The area of cross section b) 1(1 = length of wire)
c) Both a & b d) The current passing through it [ ]
8) A cell emf 1.45 volts and internal resistance 4 is connected to a resistance of 1,
what current will flow
a) 2.9A b) .29A c) 29A d) 0.029A [ ]
9) The total power in a series circuit is 10 watts. There are five equal value resistors in
the circuit. How much power does each resistance dissipate
a) 10 w b) 5 w c) 2 w d) 1 w [ ]
10) An electric iron takes 2.5A at 250v, what is its hot resistance
a) 100 b) 9.2 c) 29 d) 92 [ ]
11) The basic unit of charge is the charge of an _________ But this charge is very small.
12) The energy spent at unit charge in transporting it from one terminal to the other is
called the _____________________

7. 13) The time rate of transfer of energy is called ______________________
14) Any network consists of one or more passive elements (i.e. resistances, Inductances
and capacitors) under ideal conditions resistors, inductance and capacitors are______
15) Faraday found that when the magnetic field produced by one circuit is altered,
voltage is induced in the ______________________ circuit.
16) In any network, the algebric sum of the currents in all branches meeting at a point is
_________________
17) Magnitude of emf of self inductance depends upon the rate of change of current and
_________________
18) The generation of electric energy is the conversion of various forms of energy into
______________
19) For equal value resistors are connected in parallel. Five volts are applied in parallel
circuit and 2.5mA are measured from the source. What is the value of the resistor
___________
20) Battery is an ideal voltage source (T / F)
21) In any closed path, the algebraic sum of the branch voltages around the loop is zero
of any instant (T / F)

8. UNIT – II QUIZ – II
1) For a constant currents an inductor acts as
a) Open circuit b) short circuit
c) a current source d) a finite resistance [ ]
2) For a constant voltage, a capacitor acts as
a) Open circuit b) a short circuit
c) a current source d) a finite resistance [ ]
3) What is the source in energy of hydro-electric stations
a) Steam b) coal c) oil d) water [ ]
4) The current though an inductor
a) can change suddenly b) can not change suddenly
c) is zero d) is infinite [ ]
5) The voltage across an inductor
a) can change suddenly b) can not change suddenly
c) is zero d) is infinite [ ]
6) The energy stored in an inductor is
a) ½ LI2
t b) ½ LI2
c) ½ L2
I d) LI2
[ ]
7) The energy stored in capacitor is
a) Zero b) ½ CV2
c) ½ CI2
d) CV2
[ ]
8) A capacitor is defined by
a) Q = CV b) I = cvdt c) V = L (di/dt) d) Q = CI [ ]
9) An inductor is defined by
a) I = L(dv/dt) b) I = L vdt c) V = L(di/dt) d) V = Li dt [ ]
10) The internal resistance of an ideal voltage source
a) finite b) infinite c) unknown d) Zero [ ]
11) The internal resistance of an ideal current source
a) finite b) infinite c) unknown d) Zero [ ]
12) Which of the following is correct
a) q = di/dt b) I = dq/dt c) I = q dt d) none [ ]

9. 13) Which of the following is correct
a) Energy = (Power)dt b) Power = Energy/time
c) power d/dt (Energy) d) all the above [ ]
14) The total inductance of the coils 1 & 2 connected in series as their fluxes is additive
a) L1 + L2 – M b) L1 + L2 – 2M
c) L1 + L2 + M d) L1 + L2 + 2M [ ]
15) Which of the following is correct for a coil
a) L = N d/dt b) L = N d/dI
c) L = N dI/dt d) all the above [ ]
16) There are two sine wave V1 = Vm Sin(wt) and V2 = Vm Sin(wt + /4) then
a) V1 leads V2 by 45 b) V2 leads V1 by 45
c) V1 & V2 are in phase d) V2 lags behind V1 by 45 [ ]
17) The peak value of the sine wave I = 100 Sint is
a) 100 b) 100/2 c) 50 d) –100 [ ]
18) The magnitude of the impulse function d(t) is
a) infinity b) unity c) indetermine d) Zero [ ]
19) What is the phase angle between the induction current and the applied voltage in a
Parallel RL circuit is
a) 0 b) 45 c) 90 d) 180 [ ]
20) What is the phase angle between the capacitor current and applied voltage
a) 0 b) 45 c) 90 d) 180 [ ]
21) In a certain parallel RL circuit R = 50 & XL = 75 what is the admittance
a) 0.024s b) 75s c) 50s d) 1.5s [ ]
22) A series R – L circuit has a resistance of 50 k. What its impedance and phase angle
a) 56.58, 59.9 b) 59.9k
c) 59.9,56.58 d) 5.99, 56.58 [ ]
23) In a given RLC circuit R = 0, Xc is 150 and XL is 80 what is its total impedance?
What is the type of reactance
a) 70, inductive b) 70, capacitive
c) 70, resistive d) 150, capacitive [ ]

10. 24) Apparent power is expressed in
a) Volt – amperes b) apparent power
c) watts d) VAR [ ]
25) A power factor of 1 indicates
a) purely resistive circuit b) Purely reactive circuit
c) combination of both a & b d) none [ ]
26) For a certain load, the true power is 100w and the reactive power is 100VAR. what is
the apparent power
a) 200 VA b) 100 VA c) 141.4 VA d) 120 VA [ ]
27) If the phase angle is 45, what is the power factor
a) Cos 45 b) Sin 45 c) tan 45 d) none [ ]
28) What is the phase angle at resonance in a series RLC circuit
a) 0 b) 90 c) 45 d) 30 [ ]
29) What is the total impedance of a series RLC circuit at resonance
a) equal to XL b) equal to XC c) equal to R d) Zero [ ]
30) What is the impedance of an ideal parallel resonant circuit without resistance in
either branch
a) zero b) Inductive c) capacitive d) infinitive [ ]
31) In a series RLC circuit operating below the resonant frequency, the current
a) I leads Vs b) I lags behind Vs
c) Irs in phase with Vs d) Vs lags by I [ ]
32) The peak value of a sine wave Y = 400 Sin t is
a) 400 b) 400 / 2 c) 200 d) – 400 [ ]
33) The rms value of a Sine wave Y = 400 Sint is
a) 400 b) 400 / 2 c) 200 d) – 400 [ ]
34) The Q- factor of a circuit can be increased by
a) increasing BW b) decreasing BW
c) increasing R d) none [ ]

11. 35) At certain frequency, IL becomes equal to IC and then IT becomes zero. This
condition is known as
a) series resonance b) parallel resonance
c) Both a & b d) none [ ]
36) In series circuit of L = 15MH, C=0.015F and R = 80 what is the impedance at the
resonant frequency
a) (15mH)w b) (0.015F)w c) 80 d) 0.015 / w [ ]
37) What is the impedance of an ideal parallel resonant circuit without resistive in either
branch
a) zero b) inductive c) infinitive d) capacitive [ ]
38) The lowest cut – off frequency is 2400Hz and the upper cut – off frequency is 2800 Hz
what is the Band width
a) 2800Hz b) 2400Hz c) 400Hz d) 5200Hz [ ]
39) The rms voltage measured across on admittance (u + jB) is V. the reactive power for
the element is
a) V2
B b) – V2
B c) V2
(u2
+ b2
)1/2
d) V2
(A + jB) [ ]
40) The power factor of the circuit is equal to the
a) Cosine of the phase angle b) Tangent of the phase angle
c) Sine of the phase angle d) Unity for reactive circuit [ ]
41) The average value of a sine wave is
a) 1 b) (Peak value) / 2 c) (Peak value) X 2 d) zero [ ]
42) The peak factor is defined as
a) VPeak / V rms b) VPeak / Vavg
c) VPeak / Time period d) none [ ]
43) Form factor is the relation between
a) Instantaneous & average values of a signal
b) RMS & average values of signal
c) Apparent value & average of a signal
d) DC value of signal [ ]
44) What is the other name of RMS value
a) form factor b) effective value
c) Maximum value d) Average value [ ]

12. 45) The ratio of true power to apparent power is
a) Energy b) Power factor c) error d) Peak factor [ ]
46) In a purely resistive load, the true power is 5 watts and its apparent power is_______
47) If 1/ 2 is the power factor then phase angle is ____________________
48) EMF equation may be written e = Em Sint where e is _________________
49) The product of VI called ___________________ and is measured in__________
50) The ratio of active power to apparent power is _____________________

13. UNIT – III QUIZ – III
PART – A
1. In a poly phase system the emfs, currents and phase angles are equal for each
phase is known as _________________
Ans: Balanced system
2. ______________________ is defined as the ratio of Resonant frequency f0 to the
3-dB Band width.
Ans: Selectivity of Resonant
3. In unbalanced 3-phase network the three line currents are ___________ and the
phase difference between them is ________________.
Ans: Unequal, equal
4. The expression 3 VL IL Cos gives the power in a 3-phase balanced system,
regardless of the connection __________________________ .
Ans: Configuration
5. If the lower cut-off frequency is 2400 Hz and the upper cut-off frequency is 2800
Hz the Band width is ______________ .
Ans: 400 Hz
6. The Q of a circuit can be increased by decreasing __________________ .
Ans: Band width (BW)
7. The voltages of a balanced ABC sequence is phasor domain are ______________
Ans: Vp 00, Vp-1200 and Vp1200
8. A 3-phase system supply 25 KW at 0.8 p.f, the line pressure being 250 Volts.
Calculate the line current and the phase current when the load is star connected
_____________________ .
Ans: 72.16 Amp
9. A 3-phase system supplies 25 KW at 0.8 p.f, the line pressure being 250 Volts.
When the load is mesh connected, the phase current is ________________.
Ans: 125/3 or 41.67 Amp
10. The moving Iron instruments are __________ types and their names are
__________________________________.
Ans: two, Attraction type and repulsion type
11. The two types of moving cost instruments are ____________________________
Ans: Permanent Magnet type and Dynamometer type
12. The magnetic effect is used in measuring instruments for the measurement of
voltage, current and power for __________________ supply.
Ans: a.c and d.c
13. The essential Features of the indicating in instruments are __________________
Ans: Deflecting torque, controlling torque and Damping Device

14. 14. Controlling Devices are ________ types and write their names _______________
Ans: Two, Spring Control and gravity control
15. The spring control material should have ____________________________ .
Ans: Specific resistance
16. The three method of damping are provided in measuring instruments and their
names are _______________________________________________________.
Ans: Pnewmatic Damping, Electromagnetic Damping and fluid friction
damping
17. The expression for damping torque is _______________________ .
Ans: x B2 l2 v / R m.nw.
18. On the Basis of British standards these are ____________________ grades of the
instruments about the accuracy of instruments.
Ans: Three (sub standard, first grad, second grade)
19. The ammeter and voltmeter will work on the same principle. One Ammeter is
________________ resistance.
Ans: Core
20. The voltmeter when connected in parallel to the circuit for measuring voltages, it
does not take ________________________________.
Ans: Appreciable current

15. UNIT – III QUIZ – III
PART – B
1. Name the main parts of a D.C. machine.
2. What is the necessity of a commutator in a D.C. machine?
3. Write the emf equation of a D.C. generator if it is a) lap wound b) wave wound.
4. Name the various loss in a D.C.machine.
5. What are stray losses is a D.C. machine?
6. Write an expression for the efficiency of a D.C. generator
7. What is the condition for maximum efficiency of a generator?
8. What is the effect of armature reaction in a D.C. generator?
9. What conditions should be satisfied if two generators are to be paralleled?
10. Name the types of D.C.generators.
11.Draw the saturation characteristics (or open circuit characteristic) of a D.C.shunt
generator
12. What are the conditions for the voltage build up of D.C.shunt generator?
13. Draw the external characteristic of D.C. shunt generator.
14. Draw the internal characteristic of D.C. shunt generator.
15. Draw the external characteristic of D.C. compound generator.
16. Draw the external characteristic of D.C. series generator.
17. Write the equation for the force developed in D.C.motor.
18. What is back emf in D.C. motors?
19. Write an expression for back emf in D.C.motors.
20. Write the condition for maximum power in D.C. motors.
21. Write an expression for the torque developed in a D.C. motor.
22. Define speed regulation of D.C.motor.
23. Draw the output current versus speed characteristics of D.C a) series motor
b) shunt motor c) compound motor
24. What is the difference between cumulative –compound motor and differential-
compound motor?
25. Draw the efficiency characteristic of a D.C. motor.
26. Name the various losses in a D.C. motors.
27. What are the methods of controlling the speed of D.C.motors?
28. What is the necessity of starter for a D.C. motor?
29. Write the disadvantages of swinburne test?
30. How do you change the direction of rotation of d.c.shunt motor?

16. UNIT – IV QUIZ – IV
PART – A
1. D.C. Motor ________________ electric engineering into mechanical energy.
Ans: Converts
2. ___________________ produces electrical power.
Ans: DC Generator
3. When D.C Machine is rotated by external device and produces ___________.
Ans: Electrical Energy
4. When D.C Machine is connected to D.C Supply and produces ___________.
Ans: Mechanical Energy
5. In a D.C. Machine the direction of rotation depends on the direction of
armature current and pole flux. The direction of rotation depends by the
application of ________________.
Ans: Fleming’s Left Hand Rule
6. In D.C. Motor the induced e.m.f is called the ________________.
Ans: Back emf (Eb)
7. D.C Motor is classified ___________ types depending upon the principles of
fields coils.
Ans: Three
8. In D.C Shunt motor the equation Eb Ia is used to produce mechanical power.
Ans: Eb Ia
9. The torque equation in a D.C. Motor is ____________________.
Ans: ( )
81
.
9
2
1

QZ Ia
A
P
Kg – m
10. The speed equation in a D.C. Motor is ____________________.
Ans: N 
f
a
a
I
R
I
V 
 )
2
1
(
A
P
QZI
I
E
a
f
b

Nw - m
11. In a D.C. Machine, there are ___________ types torques.
Ans: three
12. At the time starting, the D.C Motor takes heavy current due to absence of
_________________________.
Ans: Back emf
13. A variable resistance is connected in series with the armature winding known
as _______________________________.
Ans: Starter
14. Speed Control of D.C Motors by the following three methods ___________
Ans: (a) by changing applied voltage (b) by changing armature resistance
(c) by change filed current

17. 15. The field current of shunt motor is varied by connecting variable resistance
‘R’ in series with field winding and the resistance is also called ___________.
Ans: Regulator
16. By which D.C. Motor, the speed remain almost constant from no load to full
load ___________________________.
Ans: D.C Shunt Motor
17. Define separate excitation of D.C. Generator _______________________.
Ans: Field magnets are exited from an entirely separate D.C Source.
18. How many types of D.C Generators on the principle of self excitation and
name them _______________________________________.
Ans: Three types – Shunt, Series & Compound.
19. D.C Series generators are scarcely used as ________________________ .
Ans: Boosters
20. In a gives D.C. Compound generator, how the field magnets are excited?
Ans: Partly by shunt costs and partly be series costs

18. UNIT – IV QUIZ – IV
PART – B
1. Is the transformer in the laboratory shell type or core type?
2. Define the transformation ratio.
3. Find the transformation ratio if the primary of the transformer has 600 turns and the
secondary has 60 turns.
4. write the emf equation of a transformer.
5. Draw the vector diagram of a transformer on no-load.
6. Name the two components of no-load current of transformer.
7. Write an expression for finding the no-load power-factor of transformer.
8. Is the no-load power represents iron loss or copper loss? Why?
9. What is percentage of no-load current compared to full-load current?
10. Draw the equivalent circuit of a transformer.
11. Draw the vector diagram of a transformer on full-load and lagging power-factor.
12. Why is transformer rating giving in KVA?
13. What parameters of the transformer do you get if you conduct short-circuited test.
14. The wattmeter connected in the short-circuited test gives iron loss. True or false?
Why?
15. Define regulation of a transformer.
16. Which test will give you the necessary data to find the regulation of a transformer?
17. Define the efficiency of a transformer.
18. What is the condition for getting maximum efficiency of a transformer?
19. Write an expression to find load KVA corresponding to the maximum efficiency.
20. Define all-day efficiency.
21. What meters do you use to conduct experiments on transformers?
22. Why do you use an autotransformer?
23. How many windings will there be in an autotransformer?
24. What power supplies are you using for conducting tests on transformer?
25. Define primary and secondary of a transformer.
26. Name the two types of three-phase induction motors.
27. Why is three-phase squirrel cage induction motor preferred to slip-ring induction
motor?
28. Is a three-phase induction motor self-starting?
29. Write an expression for the rotor-induced emf in terms of stator supply voltage for
induction motor.

19. 30. Write an expression for the maximum torque at any slip for a three-phase induction
motor.
31. Write the condition for maximum torque at any slip for a three-phase induction
motor.
32. Draw a characteristic to show the relation between torque and slip for a three-phase
induction motor. Note the starting torque and maximum torque. Mark the normal
operating region.
33. Find the ratio of starting torque to maximum torque in three-phase induction motor.
34. Relate the rotor output to stator input and various losses of an induction motor.
35. How do you change the direction of rotation of three-phase induction motor?
36. What are the tests needed to predetermine characteristics of three-phase induction
motor?
37. How many tests do you do to draw the circle diagram? What are they?
38. What will the y-axis represent in the circle diagram? What will the x-axis represent?
39. What quantities do you measure in no-load test of a three-phase induction motor?
40. What quantities do you measure in rotor-block test of a three-phase induction motor?
41. Where is the field situated in an altenator?
42. Give the relation between speed, frequency and number of poles is an alternator.
43. Write an expression for the emf induced in the alternator?
44. Define form-factor. How much is form-factor for sinusoidal waveforms?
45. Define voltage regulation of an alternator.
46. What tests do you perform to predetermine the regulation of an alternator by
synchronous impedance method?
47. Draw the vector diagram of an alternator under load at a) unity power factor b)
lagging power factor c) leading power factor.
48. Explain why synchronous motor is not self-starting.
49. Draw the V curves of synchronous motor.
50. Draw the inverted V curves of synchronous motor.

20. UNIT – V QUIZ – V
1. What are the main classifications of measuring Instruments and write their names.
2. How many types of Instruments generally used in electrical engineering and what
they are?
3. How many essential features of indicating instruments are there and write their
names.
4. Write the Damping torque expression in the case of indicating instruments.
5. What are the important errors occur in Ammeters and Voltmeters.
6. How many types of Moving iron instruments and what they are?
7. State one of the advantage of moving Iron instruments
8. Write the names of two types of Moving coil instruments.
9. What is the permanent magnet type of moving coil instruments?
10. Write any one limitation of moving coil instruments.
11. Write the most important application of moving coil systems in measuring
Instruments.
12. On what supply the induction type of instruments used either an ammeter or a
voltmeter or a wattmeter.
13. What are the type of adjustments of the energy meter a write their names.
14. How many types of energy meters are there and write their names.
15. Draw a current diagram for measurement of two wattmeter method for
measurement of three phase balanced load systems.
16. Draw the connection diagram of energy meter for three phase balanced load
systems.
17. What are the types of adjustments of the energy meter and write their names.
18. The single phase meter consists of two…………….. coils and two……….. coils.
19. The increase of temperature affects the reading in moving Iron Instruments due to
……………………. the resistance of the coil.
20. In practice it is very difficult to design a shunt for a range of moving Iron meters,
so the shunts are …………………… used with moving iron instruments.

21. MODEL PAPER – I
1. a) State and explain Kirchoffs Laws.
b) Find the equivalent Resistance between A and B.
2. a) Briefly explain how alternating voltages are generated.
b) A square coil of 10cm side and 100 turns is rotated at a uniform speed of 1000
revolutions per minute, about an axis at right angles to a uniform magnetic
field of 0.5wb/m2
. Calculate the instantaneous value at induced electromotive
force, when the plane of the coil in i) at right angles to the field ii) in the plane
of the field
3. a) What do you understand by power factor? How can it be improved?
b) In a series parallel circuit the parallel branches A and B are in series with C.
The impedances are ZA = (4+j3); ZB = (4-j16/3); ZC = (2+j8) ohms. If the
current IC = (25+j0), draw the complete phasor diagram determining the
branch currents and voltages and the total voltage. Calculate the complex
power for each branch and the whole circuit.
4. a) Give a brief note on lap and wave windings.
b) A lap connected d.c. generator has 8 poles and 120 shots with 8 conductors in
each slot . If the flux/pole is 0.035Wb(I) find the emf generated when the speed
is 600 rpm. ii) What should be the speed of rotation if the induced emf is to be
500V?
5. a) Why is the speed of a shunt motor practically constant?
b) Draw the characteristics of shunt and series motors.
6. a) On what factors the induced emf in the transformer windings depends. Justify
the answer with appropriate derivation.
b) A double wound 1-phase transformer is required to step down from 1900V to
240V, 50Hz. It is to have 1.5V per turn. Calculate the required number of turns
on the primary and secondary windings respectively. The peak value of flux
density is require to be not more than 1.5 wb/m2
. Calculate th required cross
sectional area of the steel core. If the output is 10KVA, calculate the secondary
current.

22. 7. a) Draw the slip torque characteristics of an induction motor and mark the
operating region.
b) A 3-Phase, 6 pole, 50Hz induction motor has a slip of 1% at no load and 3% at
full load. Find
i) Synchronous speed ii) No load speed iii) Full load speed
iv) Frequency of rotor current at stand still
v) Frequency of rotor current at full load.
8. a) Sketch and describe the construction of a moving coil ammeter and give the
principle of operation.
b) A moving coil instrument gives full scale deflection with 15mA and has a
resistance of 5. Calculate the resistance of the necessary components in order
that the instrument may be used as i) a 2A – Ammeter ii) a 100V voltmeter.

23. MODEL PAPER – II
1 a) Derive the formulas used for star-delta Transformation.
b) Find the equivalent resistance between A and B using Star-delta transformations.
2. a) Define cycle, frequency, Phase of a periodic quantity.
b) A sinusoidal alternating current of frequency 60Hz has a maximum value of 120A.
Write down the equation for its instantaneous value. Reckoning time from the
instant the current zero and id becoming positive find i) the instantaneous value
after 1/360 second and ii) the time taken to reach 96A for the first time.
3. a) Give the expression for admittance when R,L,C are connected in parallel across a
voltage source of V volts.
b) two circuits, the impedance of which are given by Z1 = (15 + j12)  and Z2 =
(8-j5) are connected in parallel. If the potential difference across one of the
impedances is (250+jo0)V, calculate I) total current and branch currents ii) total
power and power consumed in each branch and iii) overall power factor and power
factor of each branch.
4. a) What purpose is served by the pole shoe in a d.c. machine?
b) What are the advantages and disadvantages of carbon brushes?
c) Why do we use slotted armature in a d.c machine?
d) Why is armature winding placed on the rotor of a d.c. machine?
5.a) Give two applications each of DC shunt, series and compound motors.
b) Can a dc series motor be started on no load? Give the reason?
c) Give the characteristics of cumulative and differential compound motors.
6. a) Derive the EMF equation of a transformer.
b) In no load test on a 1-phase transformer the following test data were obtained.
i) Primary voltage 220V ii) Secondary voltage 110V iii) primary current
0.5A iv) Power input 30Watts iv) power input 30watts v) Resistance of
primary winding = 0.6
Calculate a) turns ratio b) magnetizing component of n load current. c) working
component of no load current. d) iron loss.

24. 7. a) Derive the torque equation of an induction motor.
b) A 3 PHASE 50 Hz, induction motor is wound for 8 poles. If the full load slip is
2.5%, calculate
i) Synchronous speed ii) slip speed iii) Rotor speed iv) Rotor frequency.
8. a) Describe with the aid of sketches, the effect on a current carrying conductor lying in
and at right angles to a magnetic field?
b) The coil of a moving coil instrument is wound with 401/2
turns. The mean width of
coil is in 4cm and the axial length of the magnetic field is 5cm. If the flux density in
the gap is 0.1 T. Calculate the torque in Newton meter when the coil is carrying a
current of 10mA.

25. MODEL PAPER – III
1. a) define the following terms:
i) Magnetomotive force ii) Ampere-turns iii) Reluctance
iv) Permenance v) Reluctivity
b) Bring out analogy between Electrical and Magnetic circuits.
2. a) What is the significance of the r.m.s. and average values of a wave?
b) Calculate the RMS value of the function, if it is given that for 0<t<0.1,
y=10(1-e-100t
) and for 0.1<t<0.2, y=10e-50(t-0.1)
.
3. a) Define admittance, susceptance and conductance.
b) The currents in each branch of a two-branched parallel circuit are given by the
expressions Ia = 7.07 Sin(314t-/4) and Ib = 21.2 Sin(314t+/3). The supply
voltage is given by the expression V = 354 Sin314t. Derive a similar expression
for the supply current and calculate the ohmic value of the components, assuming
two pure components in each branch. State whether reactive components are
inductive or capacitive.
4. a) What are the advantages and disadvantages of using large number of poles in a d.c.
machine?
b) An 8 pole lap wound d.c. generator has 120 slots having 4 conductors/slot. If each
conductor can carry 250A and if flux/pole is 0.05Wb, calculate the speed of the
generator for giving 240V on open circuit. If the voltage drops to 220V on full
load, find the rated output of the machine.
5. a) In a brake-test on a small shunt motor, the speed was 1500rpm, the load on one side
of brake band was 15.2cm. If the input current was 2A at 250V, calculate i) the
torque ii) the efficiency.
b) Explain swinburne’s method for determining efficiency.
6. a) How do you classify the transformers based on constructions and why the
transformer core is laminated.
b) A 250/500V transformer gave the following test results.
Short circuit test: 20V; 12A, 100Watts on HV side
Open circuit test: 250V, 1A, 80Watts on LV side
Calculate the efficiency when the output is 10A, 500V and 0.8 power factor
lagging.
7. a)What is an alternator and what is its principle of operation?
b) A 600V, 60KVA, 1-phase alternator has an effective resistance of 0.2 Ohms. A
field current of 10 Amps produces an armature current of 210 Amps on short circuit
and an EMF of 480V on open circuit. Calculate
i) synchronous impedance ii) Synchronous reactance iii) Full load regulation
at 0.8P.F lagging.

26. 8. a) Explain with the aid of a circuit diagram, how a DC voltmeter may be calibrated by
means of a potentiometer method.
b) A moving coil instrument, used as a voltmeter, has a coil of 150 turns with a width
of 3cm and an active length of 3cm. The gap flux density is 0.15T. If the full-scale
reading is 150V and the total resistance of the instrument is 100000 find the
torque exerted by the control springs at full scale.

27. MODEL PAPER – IV
1 a) Derive the formula for Force an a current carrying conductors.
b) Find magnetic intensity at point ‘P’, is 2m away from a conductor carrying a current
of 5 amperes.
2. a) Define Root mean square value, Average value of an alternating quantity
b) For the sinusoidal wave form calculate R.M.S. and Average values.
3. a) Define Quality factor, Selectivity of a resonant circuit.
b) A circuit of a resistance 12, a capacitance of 320F and an inductance of 0.08H,
all in series. A supply of 240V, 50Hz is applied to the ends of the circuit. Calculate
i) the current in the coil ii) the potential difference across each element of the circuit
and iii) the frequency at which the current would have unity power factor.
4.a) A four pole d.c generator runs at 750rpm and generates an emf of 240V. The
armature is wave wound and has 792 conductors. If the total flux per pole is
0.0145wb, what is the leakage coefficient?
b) A 1500KW, 550V, 10 pole generator runs at 150rpm. There are 2500 lap connected
conductors and the full load copper losses are 25KW. The air gap flux density has a
uniform value of 0.9wb/m2
. Calculate i) The no load terminal voltage ii) The area
of pole shoe.
5. a) with a neat sketch, explain the operation of three point starter.
b) If the load is removed from a dc series motor in operation, what will happen?
6. a) Explain the principle of operation of a 1 – phase transformer.
b) A single phase transformer has 400 primary and 1000 secondary turns. The net
constructional area of the core is 60 cm2
. If the primary winding is connected to a
50Hz supply at 520V, Calculate
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 the windings.
7. a) Define % voltage regulation and how do you find voltage regulation of an alternator
experimentally.
b) A 3-phase, 4 pole star connected turbo alternator has a cylindrical rotor. The
reactance and resistance per phase of winding is 2.5 Ohms and 0.15 Ohms. The
alternator has terminal potential difference 0f 6600V. when delivering a current of
250Amps. Calculate i) The generated EMF at 0.6 PF lagging ii) The regulation at
0.6 PF lagging.
8. a) Give a summary of four different types of voltmeters commonly used in practice.
State whether they can be used for AC or DC circuits. In anyone case, give a sketch
showing the construction, showing the method of control and damping employed.
b) A DC voltmeter has a resistance of 28600. When connected in series with an
external resistor across a 480V DC supply the instrument reads 220V. What is the
value of the external resistance?

28. DISCRIPTIVE QUESTIONS
UNIT – I
1. (a) State and Explain Faraday’s Law of electromagnetic induction with examples.
(b) The combined inductance of the two coils connected in series is 0.75 H and 0.25 H
depending on the relative directions of currents in the coils. If one of the coils,
when isolated, has a self inductance of 0.15 H, then calculate (i) coefficient of
coupling.
2. (a) State and explain Lenz’s law with examples.
(b) A circular soft iron ring and a cross bar of silicon steel is fitted into the former as
shown below with relavent data. The cross-sectional area of ring is 12cm2
and that
of the cross-bar is 2 cm2
. Estimate the required ampere-turns to be applied to one-
half of the ring to produce a flux density of 1.25 wb/m2
in the other half.
3. (a) Derive the relation between reluctance, m.m.f. and flux of a magnetic circuit.
(b) A cast steel ring has a circular cross-section 3 cm in diameter and a mean
cirucumference of 80 cm. The ring is wound with a coil of 600 turns:
(i) Estimate the current required to produce a flux of 0.5m Wb in the ring.
(ii) If a saw cut 2 mm wide is made in the ring, find approximately the flux
produced by the current found in (i). Find the current value which produces the
same as in (i).
Neglect fringing and leakage effects. The magnetization curve of cast steel is :
B(T) H (A/m)
0.1 170
0.2 300
0.3 380
0.4 460
0.5 540
0.6 630
0.7 740
0.8 900
4. a) State and Explain Kirchhoff’s laws.
b) For the d.c. circuit shown below, calculate the power delivered to the 10 ohm
resistance and also the voltage across the 6 ohm resistance.

29. 5. Determine the current required in a magnetizing winding having 300 terms wound
on a magnetic care shown in figure.
Mean dia of the ring = 20 cms. Relation permeability of the material is 500.
Magnetic flux to be established in air gap is 0.5 wb.
6. a) Derive the star-delta transformation for a resistance network.
b) State and explain Faraday’s law of electromagnetic induction. Distinguish between
self and mutual inducd emfs.
7. a) Define self- inductance mutual inductance and coefficient of coupling. Derive the
relation ship between them.
b) Two identical coils when connected in series gave a total inductance of 40mH.
When one of the coils is reserved the total inductance is 10mH. Determine the self
and mutual inductance and co-efficient of coupling.
8. a) Derive the expression for force on a current carrying conductor placed in a magnetic
field.
b) Define self and mutual inductance. What is coefficient coupling .Derive the relation
between them.
9. Find the voltage drop across 2 ohms (Shown in Fig. 1.)

30. UNIT – II
1. a) Find the rms and average values of waveform in the following figure.
b) Draw the phasor representing the following electrical quantities taking the X-axis as
reference vector: v = 100|0, i1 = 10 |-30 , i2 = 20 with a power factor of 0.8 leading
with respect to voltage ‘v’ and hence find the resultant of i1 and i2 geometrically.
2. A series circuit having R=100; L = 0.12 H and C = 28.27 F is fed from a 100V,
50 Hz supply. Find the current, active power, impedance, r.m.s. values of voltages
across the resistance, inductance and capacitance. Draw a phasor diagram showing
all the voltages and current taking the applied voltage as reference.
3. Find the R.M.S. Value, average value and form factor for the wave form shown in
Fig.
4. a) In a 3-phase balanced system obtain the relations between the phase and line values
for voltages and currents when the system is (i) in star and (ii) in delta.
b) Three resistances each of 100 ohms are connected in star across a 3-phase supply. If
the line current is 1A, Calculate the total power absorbed.
5. a) Show that average power in a purely inductive circuit is zero.
b) A 60 Hz voltage at 230V effective value is impressed on an inductance of 0.265H.
i) write the time equation for the voltages and the resulting current, Let the zero axis
of the voltage wave at = 0. ii) Show the voltage and current on a phasor diagrams
and iii) find the maximum energy stored in the inductance.
6. a) What is meant by Active power, reactive power and apparent power.
b) A coil of R = 4, XL = 3 connected in series with a condenser of R=8, XC = 8,
this combination is connected to 4 resistor. Across this series circuit a voltage
1000 is applied. Calculate I) current ii) voltage drops across coil, condenser and
resistor and iii) power absorbed by the circuit. Take voltage vector along the
reference axis.

31. 7. a) Show that average power in a pure capacitor is zero.
b) A 50 Hz voltage of 230 V effective value is impressed on a capacitance of 26.5F.
i) Write the time equation for the voltage and the resulting current. Let the zero axis
of the voltage wave be at t = 0. ii) Show the voltage and current on a time diagram.
iii)Show the voltage and current on a phasor diagram iv) find the maximum energy
stord in the capacitance. Find the relative heating effects of two current waveforms
of equal forms of equal peak value, the one sinusoidal and the other rectangular
wave form.
8. a) A 230 V, 50 Hz single phase supply is feeding following loads which are connected
across it
i) a motor load of 4KW, 0.8 lagging p.f.
ii) A rectifier of 3KW at 0.6 leading p.f.
iii) A lighter load of 10KVA unity p.f.
iv) A pure capacitive load of 8KVA
Determine total KW, total KVAR.
b) A coil of resistance 15  and inductance of 0.05H is connected in parallel with a
non-inductor resistance of 20.Find (i) the current in each branch (ii) the total
current (iii) the phase angle of whole arrangement for a applied voltage of 200V at
50 Hz.
9. a) A voltage of V = Vm Sint is impressed across R-L-C series circuit. Find the
expression for current and power.
b) A resistance of 20, an inductance of 0.2H and a capacitance of 100F are
connected in series across 220V, 50 Hz mains. Determine the following i)
impedance ii) current iii) voltage across R,L and C iv) power in watts and VA and
v) p.f. and angle of lag.
10. a) Why the inter connection is needed in a 3 system? Explain about phase sequence.
b) Three similar coils, each having a resistance of 20 and an inductance of 0.05H all
connected in (i) star (ii) mesh to a 3-phase, 50 Hz supply with 400Vbetween lines.
Calculate the total power absorbed and the line current in each case. Draw the
vector diagram of current and voltages in each case.
11. a) A voltage of V = Vm Sint is impressed across R-L-C series circuit. Find the
expression for current and power.
b) A tungsten filament bulb rated at 500 W, 100 V is to be connected to series with a
capacitance across 200V, 50Hz supply. Calculate (i) the value of capacitor such
that the voltage and power consumed by the bulb are according to the rating of the
bulb (ii) the power factor of the current drawn from the supply and (iii) draw the
phasor diagram of circuit.
12. a) Deduce the relation between line voltage, line current and phase voltages, phase
currents in a delta connected network.
b) A three phase 400V, 50 Hz a.c. supply is feeding a three phase delta connected
load with each phase having a resistance of 25 an inductance of 0.15H and a
capacitance of 120F in series. Determine the line current, volt-amp, active power
and reactive volt-amp.

32. UNIT – III
1. a) Derive torque equation for a d.c. motor.
b) A 500 V shunt motor takes 4 A on no load. The armature resistance is 0.2, and
field current is1 A. Estimate the efficiency, when the input current is 100 A.
2. a) Using the standard notations, obtain the e.m.f. equation for a d.c. machine.
b) A d.c. shunt generator has an induced voltage on open circuit of 127 V. When the
machine is on-load, the terminal voltage is 120 V. Find the load current if the field
resistance is 150  and armature circuit resistance 0.02.
3. a) A 500 V shunt motor takes 4 A on no-load. The armature circuit resistance is 0.02 
and the field current is 14. Find the output and the efficiency when the input current
is 80A.
b) What are the different types of D.C. motors ? Draw their characteristics and
explain.
4. a) Explain the conditions required for the build up of emf of a self excited D.C.shunt
generator.
b) What is critical field resistance and how it is determined experimentally?
c) A 4 pole d.c. shunt generator is delivering 20A to a load of 10 ohms. The armature
resistance is 0.5 ohms and shunt field resistance is 50 ohms. Calculate the induced
emf and the efficiency of the machine.
5. a) Deduce the speed-torque characteristics of d.c.shunt and series motor and discuss
the applications of these motors.
b) 250 V, d.c. shunt motor has a full load armature current of 40A and a speed of 1000
rpm. The resistance of the armature is 0.2 ohms. What resistance must be added in
series with armature to reduce the speed by 25% for the same load torque?
6. a) Briefly explain the principle of operation of dc generator.
b) Calculate the flux in a 6-pole dc generator with 780 armature conductors, generating
500v, when running at 1000if the armature is (i) lap wound (ii) wave wound.
c) Calculate the emf generated by a 6-pole wave wound armature having 45 slots with
18 conductors. The flux per pole is 0.025wb. The armature is driven at 1000 rpm.
7. a) Explain DC motor principle and its working.
b) A 250 V shunt motor on no-load runs t 1000 rpm and takes 5A. The total armature
and shunt field of resistances are 0.2 and 250 respectively. Calculate the speed
when loaded and taking current of 50A if armature reaction weakers the field by 3%.

33. 8. a) Derive an expression for the emf induced in a d.c. generator.
b) Calculate the value of emf generated in an 8-pole lap wound generator if it is rotated
at 250 rpm. The flux perpole is 0.05 wb and the number of armature conductors is
960.
c) A 6-pole wave connected armature has 250 conductors and runs at 1200 revolutions
per minute. The electromotive force generated is 600v. Find the useful flux per pole.
9.a) Explain the significance of back emf in a dc motor and explain how it controls the
values of armature current in a dc motor.
b) A 250v shunt motor takes a total current of 20A. The shunt field an armature
resistances are 200 and 0.3 respectively. Determine (i) value of of back emf (ii)
gross mechanical power in in the armature.
c) A 230V motor has as armature circuit resistance of 0.6. If the full load armature
current is 30A nd no-load armature current is 4A,find the change in back emf from no
load to full load.
10.a) With neat skethches, explain the construction and functions of the various parts of a
d.c. machine.
b) Calculate the emf. Generated by a 6 pole lap wound armature with 65 slots and 12
conductors per slot, When driven at 1000 rpm. The flux/pole is 0.02 wb
11.a) Give the voltage equation and power equation of a dc motor.
b) A 20 KW, 250 V dc shunt generator has armature and field resistances of 0.1 and
125 respectively. Calculate the total armature power developed when running (i)
as a generator delivering 20 KW output (ii) as a motor taking 20KW input.
12.a) What are the advantages and disadvantages of using large number of poles in a d.c.
machine?
b) An 8-pole lap wound d.c.generator has 120 slots having 4 conductors per slot. If the
generator for giving 240V on open circuit. If the voltage drops to 220v on full load,
find the rated output of the machine.
13.a) Derive an expression for the torque developed N-M and in kg-m in a dc motor.
b) Determine the value of torque in kg-m developed by the armature of a 6-pole wave
wound motor having 492 conductors, 30 mwb per pole when the total armature
current is 40A.

34. UNIT – IV
1. a) Describe the construction of the single-phase transformer.
b) A 230/115 V, 1- transformer takes an input of 350 VA to no load and at rated
voltage. The core loss is 110 W. Find:
(i) The iron loss component of no load current
(ii) Magnetising component of no load
(iii) No load P.f.
Assuming the rating of the transformer a 3kVA and full load copper loss as 400W,
also calculate its maximum efficiency at unity p.f.
2. a) Explain the principle of operation of an alternator.
b) A 3-phase, 2,500 kVA, 6600 V, star connected alternator has an armature reistance
of 0.073  per phase and a synchronous reactance of 10.7  per pahse. Calculate
the voltage regulation at full load (i) 0.8 p.f. lagging (ii) 0.8 p.f. leading (iii) unity
p.f.
3. a) Explain the construction and principle of operation of a 1  transformer.
b) The following data were obtained on a 50 kVA 2400/120 volt transformer.
OC test : 120 V, 9.56 A and 396 watts on LV side,
SC test : 92 V, I = 20.8 A and 810 watts on HV side.
Find the efficiency when rated kVA is delivered to a load at 0.8 P.f. lag and
corresponding voltage regulation.
4. a) A 3 , 600 MVA alternator has a rated terminal voltage of 22kV (line to line). The
stator winding is star connected and has a resistance of 0.014 ohm per phase. The
synchronous impedance was found to be 0.16 ohm per phase. Calculate the voltage
regulation for a load having a power factor of 0.8 lagging.
b) What do you understand by synchronous impedance from OC and SC tests on an
alternator?
5. a) What are the losses in a transformer? How do they vary with load?
b) A 100KVA, two winding transformer has an iron loss of 1kW and a copper loss at
normal output current is 1.5 kW, calculate the KVA loading at which the efficiency
is maximum. Find also the efficiency at this loading at 0.8 power factor lagging.
6. a) Derive the EMF equation of an alternator clearly explaining the various factors
affecting the emf.
b) A three-phase star connected alternator has a poles and runs at 750 r.p.m. It has 24
slots per phase and 10 conductors per slot, the flux being 0.055 wb/pole. Calculate
the line voltage. Assume winding factor to be 0.96.
7. a) Explain the construction , and working principle of single phase transformer.
b) The efficiency o a 500KVA,single phase transformer is 98%, when delivering full-
load at 0.8 p.f., leading and 99% at Half-full-load at unity power factor calculate
i) Iron losses ii) Full load copper losses
8. a) Give the principle of operation (or working principle) of 3-phase Induction motor.
b) A 4-pole, 3-phase Induction motor runs at a speed of 1.440 rpm. On 500V; 50Hz
mains. The mechanical losses are 2.23 HP calculate. a) The slip b) Rotor copper
Losses c) The efficiency.

35. 9. a) Draw, and explain the phase or Diagram of a practical single phase transformer
supplying logging load.
b) A 4 KVA, 200/400V, 50 Hz, single phase transformer gave the following test
results.
No-load Test: 200V, 0.7A, 60W. (L.V. Side)
S.C. test : 9V, 6A, 21.6W (H.V Side)
Find the efficiency, and voltage regulation of the Transformer on full load at 0.9
P.F. Lagging.
10.a) Draw, and Explain the Torque-slip characteristics of 3-phase Induction motor,
showing clearly the starting Torque, maximum Torque, and normal operating
region.
b) A 3-phase induction motor, having start-connected rotor, has an induced emf of
80V,when the slip-rings are stand-still on open circuit. The rotor has a resistance,
and reactance per phase of 1 ohm, and 4 ohms respectively. Calculate the current
per phase, and P.F when a) slip-rings are short circuited, and b) slip rings are
connected to a star-connected rheostat of 3 ohms per phase.
11.a) Derive the condition for maximum efficiency and state the different losses in a case
of a transformer.
b) 3,300 / 240V, Single-Phase transformer is supplied at 249V on no-load on L.V side.
It takes 2A, and input power is 60W. if the resistance on L.V winding is 0.8 ohm,
find (i) magnetizing current (ii) active current (iii) power factor (iv) copper loss in
primary (L.V side (v) core loss in transformer.
12.a) “An induction motor cannot run at synchronous speed”. Give reason
b) A 4-pole, 50Hz,3-phase induction motor runs at 1440 rpm with a load torque of 200
N-M. If the stator loses are 2,200 W, and the friction torque is 5 N-M. Calculate its
efficiency, and the rotor copper loss.
13.a) Explain in detail the O.C., and S.C., tests of single phase transformer and their use
to find regulation of a transformer.
b) Open circuit and short circuit tests on a 5 KVA, 200V/40V, 50 HZ 1-phase
Transformer gave the following Tests.
O.C. Test: 200V 1 A 100 W (L.V.Side)
S.C. Test: 15 V 10A 85 W (H.V. Side)
i) Draw the equivalent circuit referred to primary
ii) Calculate the approximate regulation of the Transformer of 0.8 P.F. lag and
leading.
14. a) Explain the construction of squirrel-cage, and phase-wound induction
motors. Mention their applications.
b) A 3-phase induction motor has 0.06 ohm rotor resistance, and 0.3 ohm stand still
resistance per phase. Find the additional resistance required in the rotor circuit to
make the starting torque equal to the maximum torque of the motor.

36. UNIT – V
1. Write short notes on any TWO of the following:
(a) Moving iron instruments
(b) Dynamometer type wattmeters.
(c) Induction type energy meter.
2. (a) Explain the construction and working of a moving coil instrument.
(b) The power consumed by a balanced 3 delta load having an impedance of 100
30per phase from 3, 440 volts line supply is measured by two wattmeter
method. What will be the two wattmeter readings?
3. (a) With the help of a neat labeled diagram, explain the principle of the permanent
magnet moving coil instrument.
(b) A moving coil instrument of resistance 0.2 ohms gives a full scale deflection with
a coil current of 1 ampere. How can this instrument be used to measure (i) Voltage
upto 200 V and (ii) Currents upto 20A.
4 . (a) Why is spring control to be preffered to gravity control in an electrical measuring
instrument?
(b) The coil a moving coil mete has resistance of 5 and given full scale deflection
when a current of 15mA passes through it. What modification must be made to
the instrument to convert it into? (i) An ammeter reading to 15A (ii) a voltmeter
reading to 15V?
5. a) Draw a diagram to show the essential parts of a modern moving coil instrument.
Label each part and state its function.
b) A moving coil millimeter has a coil of resistance 15 and full scale deflection is
given by a current of 5mA. This instrument is to be adapted to operate (i) as a
voltmeter with a full scale deflection of 100A (ii) as a ammeter with a full scale
deflection of 2A.Sketch the circuit in each case.
6. a) Describe with the diagram the construction of a repulsion type moving iron
instrument with particular reference to the means used for (i) Deflection (ii) control
(iii) damping.
b) A moving iron voltmeter in which full scale deflection is given by 100V, has a coil
of 10000turns and resistance 2000. Calculate the number of turns required on the
coil of the instrument is converted for use as an ammeter reading 20A full scale
deflection.
7. a) Explain the principle of operation of one type of moving iron instrument showing
how it is suitable for use on DC and AC systems.
b) The total resistance of moving iron voltmeter is 1000 and the coil has an
inductance of 0.765 H. the instrument is calibrated with a full scale deflection 50V
DC. Calculate the percentage error when the instrument is used on (i) 25 Hz supply
(ii) 250 Hz supply, the applied p.d being 50V in each case.