1. Motor used for elevators is generally
Explain:- Induction motor is used for elevator AC slip ring or DC compound motors are prefers for lifts. The latest design use 3− φ induction motor with variable frequency drive electronic controls
2.The characteristics of drive for crane hoisting is
Explain:- Characteristics of drive for crane hoisting–
(a) Smooth movement.
(b) Precise control.
(d) Fast speed control.
3.Heavy duty cranes are used in
Explain:- Heavy duty cranes are used in–
(a) Heavy engineering workshops.
(b) Steel-plants
(c) Ore handling plant.
Cranes uses D.C. series motor
4.The most preferred motor used in traction is:
Explain:- The most preferred motor in the traction is dc series motor.
The following features of DC series motor used for traction–
1. DC series motor robust in construction and capable.
of withstand against continuous vibration.
2. DC series motor has high starting torque.
3. DC series motor has high rate of acceleration and retardation.
4. DC series motor has develops high torque at lowspeed, low torque at high speed.
5. When DC series motor are running in parallel the all motors share almost equal load.
5.A low frequency supply is given to the single phase AC system for track electrification because
Explain:- : A low frequency supply is given to the single phase AC system for track electrification because-
• It improves commutation
• Increases efficiency
• Improve power factor
6.Which of the following is preferred for automatic drives?
Explain:- Ward-Leonard controlled d.c. motors are preferred for automatic drives. This speed control system is mainly used in colliery winders, cranes, mine hoists, elevators, steel rolling mills, traction etc
7. An electric motor may give noise due to_________________
Explain:- : Noise in electric motor– The most likely mechanical cause of noise are → warm bearing
• Moving parts rubbing together or colliding
• A bend shaft
• A loose or missing screw
• Magnetic effect
• The noise may well indicate the problem and the relevant part of motor can be inspected and repaired if necessary.
8.The speed time curve for urban service has no
Explain:- The speed time curve for urban service has no free running period. Because in urban service the stops are too close so no free running period required.
9.A locomotive exerts a tractive effort of 35,300 N in hauling a train at 48 km/h on the level
track. If the motor is to haul the same train on a gradient of 1 in 50 and the tractive effort
required is 55,180N determine the power delivered by the locomotive if it is driven by
(i)
dc series motors
(ii) induction motors.
Explain:-
10.In the speed-time curve of a train, speed in__ and time in______ are plotted.
Explain:- In speed time curve speed is given in km/h while time is rated in sec.
11.In suburban services as compared with urban service:
Explain:- In Suburban service, the distance between two adjacent stops for electric train is 1-8 Km while in Urban service the distance between two adjacent stops is 1 Km only. Therefore costing period or deceleration period is longer in suburban services as compared to urban services.
12.Which motor has widest variety of methods for speed control?
Explain:- D.C. shunt motor has widest variety of methods for speed control.
DC shunt motor has the best speed regulation i.e. for the variation in load the speed change is minimum. Hence, we can have a wide range of speed in the shunt motor applications.
The speed of D.C. shunt motor can be changed by-
1. Flux control method.
2. Armature control method
3. Voltage control method
13.A pole–changing squirrel cage induction motor employed in derricks has four, eight and twenty four pole. The lowest speed is used in :
Explain:- A pole changing squirrel cage induction motor employed in derricks has four, eight and twenty four pole. The lowest speed is used in landing the load.
14.. Match the items in List I with those of List II
and select your answers using the codes given in
the lists:
Explain:- Continuous duty – Machine tools
Short time duty – Conveyors
Continuous duty with intermittent periodic loading – Blowers
Continuous duty with starting and braking – Sirens
15.The electric drive posses the following drawback:
Explain:- The application of the drive is limited because it cannot use in a place where the power supply is not available, as it requires continuous power supply. The initial cost of the system is high.
16.Which type of load is offered by cranes and hoists?
Explain:- Reversing and heavy start loads are offered by cranes and hoists. The crane is used in transporting of heavy loads in industry. Hoist is used to lift or reduce the load with the help of lift wheel or Drum.
17.Low frequency supply is obtained by
Explain:- Motor - generator set (MG set) is a device which connects one form of energy into another form of energy. Motor-generator set is used in changing frequency voltage or phase.
Frequency changer is a electronic or electromechanical device that changes the frequency. The above two devices can be used to obtain low frequency supply.
18.In an electric traction the specific energy consumption is measured in……….
Explain:- : In an electric circuit traction the specific energy consumption is measured in watt hour ton km. Specific energy = Et/WD
Et= total energy consumption
W= Dead weight of the drain
D= Distance for which force due to resistance exists.
19.The scheduled speed of a train is…………..?
Explain:- : The scheduled speed of a train is always less than average speed. The ratio of distance covered b/w two stop and actual time of run is known as schedule speed from above is obvious that schedule speed is always smaller than the average speed.
20.During the……………period the power supply to the motor is cut-off and the train is allowed to run due to its own momentum?
Explain:- Supply on motor is cut off at the end of free running period and train is allowed to run due to its own inertia.
21.In which of the following industries, are all the motors totally enclosed and moisture proof?
Explain:- In paper industry, All motors are totally enclosed and are moisture proof. In these type of industry squirrel cage induction motor is used.
22.The crest speed in electric train is:
Explain:- The maximum speed attained by the train during the run is known as crest speed. It is denoted with 'Vm'. As the ratio of the distance covered by the train between two stops to the total time of run is the average speed.
23.In electric motor cooling; TEFC means
SSC JE 29.01.2018 Shift-IIExplain:- A totally enclosed, fan-cooled (TEFC) electric motor is a type of industrial motor with an enclosure that does not permit outside air freely circulate through the interior of motor. An external fan blows outside air over the frame of the motor to cool it.
24.Which of the following application needs frequent starting and stopping of electric motor?
Explain:- Lift and Hoist mechanism needs frequent starting and stopping of electric motor.
25.The weight of a locomotive is 120 tonnes. If the axle load is not to exceed 20 tonnes, the number of axles required is..............
Explain:- Weight of the locomotive = 120 tonns
Axle’s load = 20 tonns.
No. of axle = Weight/Load=120/ 6=20
26.Which of the following is true about coefficient of adhesion?
SSC JE 02.03.2017 Shift-IExplain:- Coefficient of adhesion is low in case of d.c. traction and high in a.c. traction.
Coefficient of adhesion=Tractiveeffort to slip the wheels/Adhesive weight
27.Which of the following indicates the usual specific energy consumption for suburban train service?
SSC JE 02.03.2017 Shift-IExplain:- 50 to 75 watt hours per tonne km indicates the usual specific energy consumption for suburban train service. Suburban train has high acceleration and also high deceleration because stations are nearer to each other in suburban-train service
28.For low and medium power drives, where speed control is not required, the motor that is recommended is.............
SSC JE 02.03.2017 Shift-IExplain:- For low and medium power drives, where speed control is not required, squirrel cage induction motor is used. It is simple in construction and it is made for upto 100 H.P.
29.Why is the energy consumption in propelling
the train required for?
i. Acceleration
ii. Work against gravity while moving up the
gradient
iii. Work against the resistance to motion
SSC JE 02.03.2017 Shift-I
Explain:- Energy consumption in propelling the train required for –
(i) Acceleration.
(ii) Work against gravity while moving-up the gradient.
(iii) Work against the resistance to motion.
30.Two locomotives having identical tractive effort-slip characteristic haul a heavy train. The locomotive with larger diameter shares......
SSC JE 02.03.2017 Shift-IExplain:-
31.Which of the following statements is true?
SSC JE 03.03.2017 Shift-IExplain:- In composite system-phase power received is converted into DC or three phase power AC system.
32.If the designation of Indian Railways locomotive is known as WAM1, then in this the letter W indicates which of the following?
Explain:- WAM-1
W = Broad gauge
A = AC electric traction
M = Mixed both goods and passenger
1 = Denotes that this locomotive is chronologically first
electric locomotive model used.
It the designation of Indian railways locomotive is known as WAMI, then in this the letter W indicates the locomotive is to run on broad gauge track.
33.An ideal traction system should have
SSC JE 03.03.2017 Shift-IIExplain:- An ideal traction system should have –
(a) High adhesion coefficient so that high tractive effort at starting.
(b) Equipment capable of with standing large temporary overloads.
(c) Easy speed control.
34.Usually wide and very sensitive speed control is require in case of...............
SSC JE 01.03.2017, Shift-IIExplain:- This system is used where usually wide and very sensitive speed control is required as for colliery winders, electric excavators, elevators and the main drives in steel mills and blooming and paper mill.
35.In case of traveling cranes, the motor preferred for boom hoist is...........
SSC JE 01.03.2017, Shift-IIExplain:- For crane travel, trolley travel and boom hoist of traveling crane requires high starting torque and constant speed in operation. Hence the slip ring induction motor is preferred.
36.Light duty cranes are generally used in ......
SSC JE 01.03.2017, Shift-IIExplain:- Light duty cranes are used in-
1.Automobile workshop
2.Pumping station
3.Power house
37.15 minutes rated motors are suitable for ......
SSC JE 01.03.2017, Shift-IIExplain:- 15 minutes rated motors are suitable for light duty cranes. A short time rating of an electric motor can be defined as the extrapolated over rating of the motor.
38.Free running and coasting periods are generally long in case of ............
SSC JE 01.03.2017, Shift-IIExplain:-
39.Battery operated trucks are used..........
SSC JE 04.03.2017, Shift-IExplain:- Battery operated trucks are used for local delivery of goods in large towns with maximum daily run up to 50-60 Km
40.Electric railway in comparison to other traction has the drawbacks of............
SSC JE 04.03.2017, Shift-IExplain:-Disadvantages of electric-traction -
(i) High initial expenditure.
(ii) Failure of supply is a problem.
(iii) Electrically operated vehicles have to move only on electric track.
(iv) For braking and control, additional equipments required.
(v) Interference with telegraphs and telephone lines.
41.The range of horse power of diesel locomotive is ............
SSC JE 04.03.2017, Shift-IIExplain:- The horse power of diesel locomotive range is 1500-2500. This system is often used on short routes.
The efficiency of this system is about 25%.
42.Which motor has to start with high acceleration?
SSC JE 20.10.2020, Shift-IExplain:- 1.Lift and city electrical train are start with high acceleration.
2. DC series motors are used in automotive hoists, lifts and cranes.
43.Choose the INCORRECT statement with respect to the DC system for railway.
SSC JE 24.03.2021, Shift-IIExplain:- DC train equipment is heavier and less efficient is incorrect, DC train equipment is very smaller and high efficient due to less loss
44.In the Kando system of electrical traction, a ____supply from the sub-station in picked up by the locomotive through the single overhead contact wire.
SSC JE 24.03.2021, Shift-IExplain:- In the kando system of electrical traction a 16 kV, 50Hz supply from substation is picked up by locomotive through’ the single overhead contact wire. It is then converted into 3-phase ac supply at the same frequency by means of phase converter equipment carried on the locomotives. Kando system work as reverse system.
45.Why is electric braking preferred?
SSC JE 03.03.2017 Shift-IExplain:- Electric braking preferred due to it is smooth and its maintenance cost is less. The energy is saved in regenerating braking