Induction Motor : 20 Marks
1. Mention three advantages of A.C. over D.C Supply.
2. Briefly explain the working principle of a three phase Induction Motor.
3. Define slip speed of a three phase induction Motor. Write the equation for determining slip.
4. What is the need of starter in 3 phase induction motor? What are the different types of starters?
5. A 3-φ 4 pole induction motor is supplied from 3φ 50Hz ac supply. Find
i. synchronous speed
ii.
calculate slip when rotor speed in 1440 rpm
iii. Rotor frequency
6. A three phase Induction Motor used in a laboratory has the following data:
Poles=6, frequency=50 c/s, voltage 440 volts rotor speed =980 rpm
Calculate synchronous speed and slip speed. Find slip value also.
7. A three phase, 7.5 H.P. Induction motor used in a Flour Mill is found to be having the following
data: Number of Poles : 4, Supply Voltage: 440 volts, Supply Frequency: 50 c/s Rotor Speed 1465
rpm. List the unknown quantities that could be computed from the above data. Compute all the
Unknown.
8. A 400 volts, 50 Hz, 4 pole 3 phase Induction Motor runs at a speed of 1400 rpm. Calculate the
synchronous speed and the slip.
9. An 8-pole alternator running at 750rpm supplies power to a 6-pole, 3-phase Induction
motor. The induction motor has a full load slip of 3%. Find the full load speed of the
induction motor and the frequency of its rotor emf.
10. A 3 phase, 4 pole, 440 V, 50 Hz induction motor runs with a slip of 4%. Find the rotor speed and
frequency of the rotor current.
11. The slip speed of a 3-phase IM is 30rpm. Its supply frequency is 50 Hz. The rotor speed is 1770 rpm. What is synchronous speed and number of poles.
12. Explain the principle of operation of a single-phase IM. Why is it not self-starting?
13. Explain the construction and principle of operation of single phase Induction Motor.
14. Give some applications of 3 phase induction motor.
15. Mention any 4 advantages of three phase Induction motor.
16. Mention any three types of Single Phase Induction motors and its application.
Alternator : 10 Marks
17. Explain the principle of operation of an Alternator.
18. Why in synchronous machine armature winding is placed on stator and field winding on rotor?
19. Distinguish between Cylindrical rotor and salient pole rotor of Alternator.
Or
Mention the types of alternator based on rotor construction and differentiate amongst them.
20. Write the Voltage equation (emf equation) of an Alternator , explain the terms and mention the
units of each of the variable used in the equation
21. A 2-Pole, 3-phase alternator running at 3000 rpm has 42 slots with 2 cod/slot.
Calculate the flux per pole required to generate a line voltage of 2300 V. Assume
Kd=0.952 & Kc=0.956
22. A single Phase Alternator used in a laboratory has the following data:
Speed: 600 rpm, Number of poles: 10, Voltage: 230 Volts.
Compute the frequency value.
23. A 6 pole, 3 phase, star connected alternator has an armature with 90 slots and 12 conductors per
slot. It revolves at 1000 rpm, the flux per pole being 0.5 wb. Calculate the emf generated, if the
winding factor is 0.97 and all the conductors in each phase are in series. The coil is full pitched.
24. An Alternator used to supply power to some place has the following data
Poles =6 Average flux per pole=0.009 Kc=0.98 Kd=0.94 T(per phase turns)=238 & E=440V
Calculate supply frequency and synchronous speed.
25. A 12 pole alternator used in a generating station runs at 500 rpm. It has the following data Flux is
0.095 wb, Kc is 0.9 and Kd is 0.95, number of turns is 800. Calculate emf value of alternator.
26. A 12 pole alternator used in a generating station runs at 600 rpm. It has the following data Flux is
0.095 wb, Kc is 0.9 and Kd is 0.95, number of turns is 900. Calculate emf value of alternator.
27. What are the different types of alternators? Explain them and mention the applications.
Introduction to Electrical Measuring Instrument : 25 Marks
28. Define the term Measuring Instruments? List out the various types of measuring instruments
29. Name any two type’s instruments classified based on methods of measurement.
30. Explain the classification of measuring instruments.
31. Mention any four important characteristic features of a measuring instruments.
32. Define the error and accuracy characteristics of measuring instrument.
33. In an experimental setup conducted in a research laboratory following data are found: Measured
value of the current: 12.45 amps. Calculated value of the current: 12.15 amps. Calculate error,
percentage error and adjustment to be made in instrument.
Identify the quantities related to error that could be found from the above data. Compute the
unknown.
34. An voltage appearing across a component of a circuit is 1.5 Volts as per the
calculations but the measured value is found to be 1.46 Volts. Calculate error, percentage error
and adjustment to be made in instrument.
35. A meter used to measure the voltage reads 127.5 Volts and the corresponding value obtained from
the computations is found to be 127.43 Volts. Calculate error, percentage error and adjustment to
be made in instrument.
36. Mention three different types of torques used in deflecting type Instruments
37. Draw the neat Diagram of a Moving Iron Instruments and name the parts. Write the Working
Principle and also the application?
38. Explain the working and construction of the instrument which can be used to measure only DC
values. Also, highlight why can’t it be used for AC systems?
39. With a neat sketch explain the construction and principle of operation of Permanent Magnet
Moving coil instrument
40. Explain the working of Energy meter with diagram.
Or
With a neat figure, explain the operation of an Induction Type meter.
41. Define Energy meter? What are the applications of Energy meter? What is the purpose of
recording system in Energy meter?
42. With a neat figure, explain the operation of a Meggar
43. What are the advantages of using Modern instruments over Traditional instruments?
44. Define virtual and digital meters with their block diagram. Also write about advantages of each
meters.
Earthing and Wiring : 25 Marks
45. Define the term electrical wiring? List out the various devices which are associated
with electrical wiring installations.
46. Write four basic components of House Wiring.
47. Draw the wiring diagram to control one lamp from two different places independently and
Write the operation table.
48. With a neat connection diagram and switching table explain the Two Point Control of a Lamp.
49. Write the circuit diagram for connecting one lamp, one fan point and one three pin Socket.
50. Draw the wiring diagram to control one lamp from two different places independently and Write
the operation table.
51. It is required to wire up a Small computer room with two lamps in Parallel. Draw the connection
diagram using two single pole switches.
52. Draw the lay out diagram and the connection diagram to carry out a wiring for a House With 2
rooms. Room -1 has 3 bulbs and 2 fan,
Room -2 has 1 bulb and 1 fan.
53. Draw the lay out and wiring Diagram for a part of the House with the following data:
Room No 1: 1 lamp Point, 1 fan Point, 1- 3 pin socket point
Room No 2: 2 Lamp Point, 1 fan Point, 1- 3 pin socket point
54. Write the circuit diagram for connecting two lamp, one fan point and one three pin Socket
55. Explain the operation of staircase wiring with neat circuit diagram
56. Explain any two wiring precaution systems to be installed in houses.
57. Draw and explain the neat diagram of a pipe earthing scheme used for domestic earthing and label
the parts.
58. What is earthing? What are different types of earthing?
59. What is the necessity of earthing?
60. What is a fuse? Why is it used in electric circuits?
61. Write a note on Safety aspects of Electrical Engineering?
62. List out the difference between the Fuse & MCB
Or
Explain about fuse and Miniature Circuit Breaker wiring protection used in house wiring.
63. Describe in brief the effects of an electric shock and the first aid requirement in such cases.
64. What precautions should be observed while installing different Electric Appliances in Houses?
Fill in the blanks of the following;
a. The slip of IM is estimated as S=______________.
b. AC generator works on the principle of __________________.
c. The ________ in alternator is decided by the frequency & speed of operation.
d. Integrating meters are used for measurement of _______________.
e. A fuse is device which is connected in ________with circuit to protect from the faults
State whether the following statements are true or false.
a. The rotor speed of an IM is always greater than synchronous speed.
b. The emf equation of alternator is 4.44*f*Ï•*Tph*Kw Volts.
c. Need of Measuring instruments is to carry out the design of various equipment and
systems.
d. Earthing means generally connected to the mass of the earth.
e. AC generators are converts electrical energy to mechanical energy,
Multi-objective questions: 10 mark
1. The basic operation of an induction motor is based on
(a) self induction.
(b) mutual induction.
(c) magnetic knocking.
(d) Lorentz Force.
2. When the supply frequency of a three phase induction motor is increased, then its
synchronous speed is
(a) decreases.
(b) increases.
(c) remain same.
(d) none of the above.
3. Induction Motor works on -----------------------
(a) Only on D.C. Source
(b) Only on A.C. Source
(c) Both on A.C.&D.C Sources
(d) Only on three Phase A.C. Source.
4. In three phase induction motor -------------------------- conductors are short circuited
(a) Stator
(b) Both Rotor and Stator
(c) Rotor
(d) Armature
5. An alternator is also called
(a) synchronous generator.
(b) turbo generator.
(c) asynchronous generator.
(d) generator.
6. Synchronous motors are
(a) not-self starting (b) self-starting.
(c) essentially self-starting.
(d) none of the above
7. Out of the list of parts mentioned below, ----------------- part is missing in Alternators
(a) Commutator
(b) Field Poles
(c) Armature Conductors
(d) Shaft
8. Synchronous Generator works on -----------------------
(a) Only on D.C. Source
(b) Only on A.C. Source
(c) Both on A.C.&D.C Sources
(d) Only on three Phase A.C. Source.
9. In Alternators field winding is kept on --------------------------
(a) Stator
(b) Both Rotor and Stator
(c) Rotor
(d) None of these
10. In a moving coil instrument, the damping torque is developed by
(a) fluid friction damping.
(b) air friction damping.
(c) eddy current damping.
(d) gravity friction damping.
11. Which of the following meter is an integrating type instrument
(a) Ammeter.
(b) Voltmeter.
(c) Wattmeter.
(d) Energy meter
12. An Alternator - I is designed to work at 5000 rpm and the Alternator-II is designed to at 500
rpm. --------------------- &-------------------- Type of rotors are to be used.
(a) Smooth Cylindrical & Salient Pole
(b) Smooth Cylindrical & Smooth Cylindrical
(c) Salient Pole & Salient Pole
(d) Salient Pole & Smooth Cylindrical
13. An Alternator - I is designed to work at Water input and the Alternator-II is designed to Work
at Steam input --------------------- &-------------------- Type of rotors are to be used.
(a) Smooth Cylindrical & Salient Pole
(b) Smooth Cylindrical & Smooth Cylindrical
(c) Salient Pole & Salient Pole
(d) Salient Pole & Smooth Cylindrical
14. Absolute Instruments are used only ------------------------
(a) In Standard Laboratories
(b) For A.C. measurements only
(c) For D.C .measurements Only.
(d) Power Measurements.
15. ---------------------------- Torque is useful in avoiding the Vibration of the pointer in Deflecting
type of instruments.
(a) Controlling
(b) Deflecting
(c) Gravity
(d) Damping
16. ---------------------------Torque is required to bring back the pointer to zero or initial position in
Deflecting type of instruments.
(a) Controlling
(b) Deflecting
(c) Gravity
(d) Damping
17. Digital Instruments have an option of storing the measured data in an appropriate memory
devices. This statement is ----------------
(a) False
(b) True
(c) Partially True
18. Virtual Instruments working as user defined Instruments need ------------------
(a) Software only
(b) Both Software and Hard ware
(c) Hardware only
(d) None of these
19. Digital Instruments has ---------------- reading error
(a) maximum
(b) least
(c) Very high
(d) None of these
20. Voltage Levels used for all the Domestic Installations are ----------------Volts
(a) 230 & 440
(b) 230 &11,000
(c) 440 &11,000
(d) 230 only
21. The Purpose of Using the Fuse Wire in Electrical Wiring is-------------------
(a) to reduce the Voltage
(b) to allow the current to flow to the earth
(c) to provide extra current during over loading condition
(d) to disconnect the circuit From the power supply during over load conditions.
22. Earthling path always must provide --------------------- to the flow of current
(a) High resistive path
(b) protection
(c) No path
(d) Very low resistive path
23. MCB is provided in the Circuit to-------------------during high currents
(a) to open the circuit
(b) to short the circuit
(c) to provide extra current
(d) to reduce the overloading
24. Earthling path always must provide to ensure
(a) Increase the magnitude of current
(b) decrease the magnitude of current
(c) Immediate and safe discharge of current
(d) quick storage of current in the circuit
25. Earth wire is connected to the
(a) ground
(b) appliance
(c) power house
(d) transformer
26. The objective of earthing or grounding is:
(a) to provide as low resistance possible to the ground
(b) to provide as high resistance possible to the ground
(c) to provide flow of positive, negative and zero sequence currents
(d) none of the above
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