UEE (UTILIZATION OF ELECTRICAL ENERGY ) TRACTION 4&5 th UNITS NOTES

Uee bits

MID-II UEE BITS

1. The advantage of electric traction over other methods is [ ]
(A) no pollution problems
(B) faster acceleration
(C) better braking action
(D) all of the above. Ans: d

2. Which locomotive has the highest operational availability [ ]
(A) Diesel
(B) Electric
(C) Steam
(D) All have same availability. Ans:b
3. Which motor is used in tramways [ ]
(A) AC single phase capacitor start motor
(B) AC three phase motor
(C) DC series motor
(D) DC shunt motor. Ans:c
3 Which braking system on the locomotives is costly [ ]
(A) Vacuum braking on steam locomotives
(B) Vacuum braking on diesel locomotives
(C) Regenerative breaking on electric locomotives
(D) All breaking systems are equally costly. Ans: c



4 The acceleration rate of trains on suburban services is [ ]
(A) 0.1 to 0.4 km phps
(B) 0.8 to 1 km phps
(C) 0.4 to 6.5 km phps
(D) 10 to 26 km phps.

Ans: c
5 The coasting retardation on trains is approximately
(A) 0.16 km phps [ ]
(B) 1.6 km phps
(C) 16 km phps
(D) 25 km phps.
Ans:a
6 The coefficient of adhesion is [ ]
(A) high on ac and dc traction systems
(B) high in case of dc traction and low in ac traction
(C) low in case of ac traction and high in dc traction.
(D) low on ac and dc traction systems Ans: c
7 The coefficient of adhesion is highest when [ ]
(A) the rails are dry
(B) the rails are oiled
(C) the rails ark wet with dew
(D) the rails are dusty. Ans: a



8. The unit of solid angle is [ ]
(A) solid angle
(B) radian
(C) steradian
(D) candela.
Ans: c
9.The unit of luminous flux is
(A) steradian [ ]
(B) candela
(C) lumen
(D) lux.


Ans:c
10 Light waves travel with a velocity of [ ]
(A) 3 x 1010cm/s
(B) 3 x 1012cm/s
(C) 3 x 1015 cm/s
(D) 3 x 1018 cm/s Ans:a
11 A train has a schedule speed of 36 km per hour on a level track. If the distance between the stations is 2 km and the stoppage is 30 seconds the actual time of run will be
(A) 260 seconds
(B) 230 seconds
(C) 200 seconds
(D) 170 seconds. Ans:d


12. B0  B0  locomotives have two bogies with [ ]
(A) four driving axles each with individual driving motors
(B) three driving axles with group drives
(C) two driving axles with group drives
(D) two driving axles with individuals drive motor. Ans :d

13. A composite system consists of [ ]
(A) a combination of diesel engine and dc series motor
(B) a combination of diesel engine and ac single phase motor
(C) single phase power received is converted into dc or three phase power ac system
(D) use of combination of dc and ac motors on the same locomotive. Ans:c
14. The speed time curve for a local train is shown in Figure. In this
AB represents [ ]





(A) Coasting
(B) Acceleration
(C) Braking
(D) Regeneration.

ANS:A


15. Area under the curve represents [ ]
(A) average speed
(B) average acceleration
(C) net acceleration
(D) distance traveled. ANS:D

16. The duration for braking is represented by the time [ ]
(A) 0-t1
(B) 0-t2 (C)t1  - t2 (D)t2- t1 Ans:d
17.Free running and coasting periods arc generally long in ease if
(A) urban service [ ]
(B) sub-urban service
(C) main-line service
(D) all of the above.
Ans:c

18. Which of the following factor affects specific energy consumption ?
(A) Distance between stops
[ ]
(B) Gradient
(C) retardation and acceleration values
(D) All of the above.
ANS:D

19. The color of light depends on [ ]
(A) wavelength
(B) frequency
(C) wavelength and frequency
(D) wavelength, frequency speed and intensity.


Ans:c


20. Sodium lamps are used for: [ ]
(A) reading rooms
(B) street lights
(C) auditoria
(D) libraries. Ans :d

21. High pressure mercury vapor lamps are generally used in [ ]
(A) factories
(B) railway yards
(C) shopping centers
(D) all of the above.
22. A train runs at an average speed of 45 kmph between stations 2.5 km apart. The train accelerates at 2 kmph and retards at 3 kmph speed-time curve may be assumed to be trapezoidal.
The maximum speed attained will be nearly [ ]
(A) 80 kmph
(B) 60 kmph (C)50 kmph
(D) 1.535 kmph.
Ans:c

23. An electric train is to have a braking retardation of 3.2 kmph. The ratio of maximum speed to average speed is 1.3, the time for stop is 26 seconds and acceleration is 0.8 kmph. The run is 1.5 km.
The schedule time is [ ]
(A) 154 kmph
(B) 180 kmph
(C) 210 seconds
(D) 240 seconds.
Ans:b
24. An electric train is to have a braking retardation of 3.2 kmph. The ratio of maximum speed to average speed is 1.3, the time for stop is 26 seconds and acceleration is 0.8 kmph. The run is 1.5 km.
The schedule speed is [ ]
(A) 25 kmph
(B) 30 kmph
(C) 45 kmph
(D) 60 kmph.
Ans:b
25. Energy consumption in propelling the train is required for [ ]
(A) acceleration
(B) work against gravity while moving up the gradient
(C) work against the resistance to motion
(D) all of the above.
Ans:d

1 Maintenance and repair cost of electric locomotives is as compared to that of steam locomotives.
Ans: less
2 The acceleration is during notching up. Ans: constant

3 During free run remains constant. Ans: speed
4 . During coasting the speed of the train . Ans: decreases
5 .Distance between stops / (Actual time of run + stop time ) is known as
  _ speed.
Ans: schedule speed
6 The maximum speed attained by the vehicle during the run is known as
  _ speed.
Ans: crest


7. in speed-time curve maximum sped (Vm)= –––––––––––––––––––-


8 Power output from the driving axles is tractive effort (Ft) X . ANS: Speed

9 The total weight of locomotive (or) train to be pulled by the locomotive is called
  _. Ans: dead weight

10 Accelerating weight( We)is _ than the dead weight( W) Ans:more

11 In main line service free running and coasting periods are whereas acceleration and braking periods are .
Ans:longer ,smaller


12 Regenerative braking is efficient and complicated in dc system as compared to that with ac system
Ans:more ,less

13 .Slipping will  take  place  when tractive effort is    between the wheel and the track
Ans:more

frictional force

14. Visible light has wavelength between A and .A . Ans: 4000 to 7500

15. Human eye is most sensitive for a wave length of A. Ans:5500
16 The color corresponding to wavelength 5500 A is . Ans :yellow and green
17 Sodium lamp is only suitable for . Ans: ac
18. Steradian is defined as the solid angle that subtends a surface on the sphere equivalent to the .
Ans: square of the radius
19. The light from a sodium lamp is nearly _ . Ans: monochromatic
20. Wavelength for color lies between that for yellow and blue. Ans:green
21:specific energy consumption=–––––––––––––––––––
22.coefficent of adhesion(µ)=–––––––––––––––– 23. 1 angstrom =––––––––––

24. Lamp efficiency is expressed in . Ans:lumens/whatt
25. Wavelength for color lies between that for yellow and blue. Ans: green

3-Phase INDUCTION MOTOR 

An electrical motor is such an electromechanical device which converts electrical energy into a mechanical energy. In case of three phase AC operation, most widely used motor is Three phase induction motor as this type of motor does not require any starting device or we can say they are self-starting induction motors. For better understanding, the principle of three phase induction motor, the essential constructional feature of this motor must be known to us. This Motor consists of two major parts:

Stator of Three Phase Induction Motor:

Stator of three phase induction motor is made up of numbers of slots to construct a 3 phase winding circuit which we connect with 3 phase AC source. We arrange the three-phase winding in such a manner in the slots that they produce one rotating magnetic field when we switch on the three-phase AC supply source.

Rotor of Three Phase Induction Motor:

Rotor of three phase induction motor consists of cylindrical laminated core with parallel slots that can carry conductors. The conductors are heavy copper or aluminium bars fitted in each slot and short-circuited by the end rings. The slots are not exactly made parallel to the axis of the shaft but are slotted a little skewed because this arrangement reduces magnetic humming noise and can avoid stalling of the motor..

Working of Three Phase Induction Motor (or)

Production of Rotating Magnetic Field:

The stator of the motor consists of overlapping winding offset by an electrical angle of 120^o. When we connect the primary winding, or the stator to a 3 phase AC source, it establishes rotating magnetic field which rotates at the synchronous speed.

Secrets Behind the Rotation: According to Faraday’s law an emf induced in any circuit is due to the rate of change of magnetic flux linkage through the circuit. As the rotor winding in an induction motor are either closed through an external resistance or directly shorted by end ring, and cut the stator rotating magnetic field, an emf is induced in the rotor copper bar and due to this emf a current flows through the rotor conductor.

Here the relative speed between the rotating flux and static rotor conductor is the cause of current generation; hence as per Lenz's law, the rotor will rotate in the same direction to reduce the cause, i.e. the relative velocity.

Thus from the working principle of three phase induction motor, it may be observed that the rotor speed should not reach the synchronous speed produced by the stator. If the speeds become equal, there would be no such relative speed, so no emf induced in the rotor, and no current would be flowing, and therefore no torque would be generated. Consequently, the rotor cannot reach the synchronous speed. The difference between the stator (synchronous speed) and rotor speeds is called the slip. The rotation of the magnetic field in an induction motor has the advantage that no electrical connections need to be made to the rotor.

Some important points of 3phase induction motor :

• Self-starting.
• Less armature reaction and brush sparking because of the absence of commutators and brushes that may cause sparks.
• Robust in construction.
• Economical.
• Easier to maintain.

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