1. Which of the following is an advantage of electric traction over other methods of traction?
A. Faster acceleration
B. No pollution problems
C. Better braking action
D. All of the above
Answer: D. All of the above
Explanation:
Advantages of electric traction systems:
- It is cleanest of all other types of systems of traction; Due to this only it is ideally suitable for the underground and tube railways
- No need of storage of coal and water that in turn reduces the maintenance cost as well as the saving of high-grade coal
- Electric energy drawn from the supply distribution system is sufficient to maintain the common necessities of locomotives such as fans, lights; therefore, there is no need of providing extra generators
- The maintenance and running costs are comparatively low
- The speed control of the electric motor is easy
- Regenerative braking is possible so that the energy can be fed back to the supply system during the braking period
- In electric traction system, in addition to the mechanical braking, electric braking can also be used that reduces the wear on the brake shoes, wheels, etc.
- Electrically operated vehicles can withstand for overloads, as the system is capable of drawing more energy from the system
- High acceleration and braking retardation
2. Which of the following is the voltage for single phase A.C. system?
A. 22 V
B. 440 V
C. 5kV
D. 15 kV
E. None of the above
Answer: A. 22 V
Explanation:
Electric Traction Systems:
- Electric traction is meant locomotion in which the driving (or tractive) force is obtained from electric motors. It is used in electric trains, tramcars, trolleybuses, and diesel-electric vehicles, etc.
- They involve the use of electric energy at some stage or the other.
- Examples: battery-electric drive, diesel-electric drive, railway electric locomotive fed from overhead AC supply, tramways, and trolly buses supplied with DC supply.
Direct Current Traction System:
- In all cases, contact systems are fed from substations which are spaced 3 to 5 km for suburban lines and 40-50 km for main lines Service.
- Substations receive power from 110/132 kV, 3-phase network (or grid). At these substations, this high-voltage 3-phase supply is converted into a low-voltage single-phase supply with the help of Scott-connected or V-connected 3-phase transformers.
- Next low AC voltage is converted to the suitable DC voltage by using suitable rectifiers or converters (like rotary converter, mercury-arc rectifier, metal or semiconductor rectifiers).
- DC motors are better suited for frequent and rapid speed control than AC motors.
- DC train equipment is lighter, less costly, and more efficient than similar AC equipment.
- When operating under the same conditions, the DC train consumes less energy than a Single-phase AC train.
- The erection cost and maintenance cost of the conductor rail is less than that of a single-phase AC system.
- No electrical interference with overhead communication lines in the DC traction system.
- The only disadvantage of the DC system is the necessity of locating AC/DC conversion sub-stations at relatively short distances apart.
Single-Phase Low-frequency AC Traction System:
- In this system, AC voltages from 11 to 15 kV at the frequency (50 Hz), (50/2 Hz), (50/3 Hz) Hz are used.
- Electric supply is taken from the high voltage transmission lines at 50 Hz, then in addition to a step-down transformer, the substation is provided with a frequency converter.
- supply is fed to the electric locomotor via a single over-head wire (running rail providing the return path).
- A step-down transformer carried by the locomotive reduces the 15-kV voltage to 300-400 V for feeding the AC series motors.
- To overcome the low power factor and commutation problem in the AC Series motor, a low-frequency AC supply is used.
- Another advantage of employing low frequency is that it reduces telephonic interference.
- Substations are 50 to 80 km apart.
Three-phase Low-frequency AC System:
- It uses 3-phase induction motors which work on a 3 kV to 3.6 kV at (50/3 Hz) supply.
- Sub-stations receive power at a very high voltage from 3-phase transmission lines at the usual industrial frequency of 50 Hz.
- This high voltage is stepped down to (3 kV to 3.6 kV) by transformers and frequency is reduced from 50 Hz to (50/3 Hz) by frequency converters.
- This system employs two overhead contact wires and the track rail forming the third phase.
- Induction motors used in the system are quite simple and robust and give trouble-free operation.
- The induction motor used in this traction system has high efficiency and the ability of automatic regenerative braking.
Kando System (Single-phase AC to Three-phase AC):
- In this system, the single-phase 16-kV, 50 Hz supply from the sub-station is picked up by the locomotive through the single overhead contact wire.
- It is then converted into a 3-phase AC supply at the same frequency by means of phase converter equipment carried on the locomotives.
- This 3-phase supply is then fed to the 3-phase induction motors.
- Kando system is likely to be developed further.
Single-phase AC to DC System:
- This system combines the advantages of high-voltage AC distribution at the industrial frequency with the DC series motors traction.
- It employs an overhead 25-kV, 50-Hz supply which is stepped down by the transformer installed in the locomotive itself.
- The low-voltage AC supply is then converted into a DC supply by the rectifier which is also carried on the locomotive.
- This DC supply is finally fed to the DC series traction motor fitted between the wheels.
- The system of traction employing 25-kV, 50-Hz, 1-phase AC supply has adopted by Indian Railway.
3. Long distance railways use which of the following?
A. 200 V D.C
B. 25 kV single phase A.C.
C. 25 kV two phase A.C.
D. 25 kV three phase A.C.
Answer: B. 25 kV single phase A.C.
Explanation:
- In Indian Railways, the electrification in main line service or long-distance service is single phase, 25 kV, 50 Hz AC supply.
- The operating voltages of vehicles for DC track electrification system are 600, 750, 1500 and 3000 V.
- Direct current at 650 – 750 V is universally employed for tramways in the urban areas and for many suburban and main line railways, 1500 – 3000 V is used.
4. The speed of a locomotive is controlled by
A. flywheel
B. applying brakes
C. gear box
D. regulating steam flow to engine
Answer: D. regulating steam flow to engine
Explanation:
- The speed of the steam engine was manually controlled.
- The worker read speed on the indicator and increased or decreased the steam flow by setting the steam flow valve.
The process of manual control could be divided into two steps:
- Observe the current speed, and then compare the actual speed and the desired speed
- Set steam flow valve according to the speed error E.
- If E is positive (which means the actual speed is lower than the desired), set the flow valve to increase the steam flow rate; the aim is to increase the actual speed.
- If E is negative (which means the actual speed is higher than the desired), the steam flow rate should be reduced.
5. Main traction systems used in India are, those using
A. electric locomotives
B. diesel engine locomotives
C. steam engine locomotives
D. diesel electric locomotives
E. all of the above
Answer: E. all of the above
Explanation:
Main traction systems used in India are
- electric locomotives
- diesel engine locomotives
- steam engine locomotives
- diesel electric locomotives
1. electric locomotives
An electric locomotive is a locomotive powered by electricity from overhead lines, a third rail or on-board energy storage such as a battery or a supercapacitor.
2. diesel engine locomotives
A diesel locomotive is a type of railway locomotive in which the prime mover is a diesel engine. Several types of diesel locomotives have been developed, differing mainly in the means by which mechanical power is conveyed to the driving wheels.
3. steam engine locomotives
A steam locomotive, or steam engine, is a steam-powered traction engine which pulls or pushes wagons or "cars" on a "road" or "way of two parallel steel tracks. Wagons carry all manner of cargo including people.
4. diesel electric locomotives
An electro-diesel locomotive (also referred to as a dual-mode or bi-mode locomotive) is a type of locomotive that can be powered either from an electricity supply (like an electric locomotive) or by using the onboard diesel engine (like a diesel-electric locomotive).
6. In India diesel locomotives are manufactured at
A. Ajmer
B. Varanasi
C. Bangalore
D. Jamalpur
Answer: B. Varanasi
Explanation:
The Diesel Locomotives Works (DLW), Varanasi, India is a production unit of Indian Railways that manufactures diesel locomotives and its spare parts.
Some of the production units of Indian Railways are listed below:
| Railways Production Units | Produces |
| Wheel Axle Plant (WAP), Bangalore | Wheel Axle Plant |
| Chittaranjan Locomotive Works (CLW, Chittaranjan) | Steam Locomotives & electric locomotives |
| Rail Coach Factory (RCF, Kapoorthala, Panjab) | Rail Coaches |
| Integral Coach Factory (ICF), Chennai | Coaching Stick |
| Diesel Component Works (DCW), Patiala | Diesel Components & parts |
| Bharat Earth Movers Ltd., Bangalore | Rail Coaches for Delhi Metro Rail Corporation |
7. For diesel locomotives the range of horsepower is
A. 50 to 200
B. 500 to 1000
C. 1500 to 2500
D. 3000 to 5000
Answer: C. 1500 to 2500
Explanation:
- The range of horsepower of diesel locomotive is 1500 – 2500
- The maximum rating of a steam locomotive is around 1500
- Electric AC power locomotives are rated at up to 6600 hp
8. ....... locomotive has the highest operational availability.
A. Electric
B. Steam
C. Diesel
D. None of the above
Answer: A. Electric
Explanation:
Electric Locomotive: -
- An electric locomotive requires much less time for maintenance and repairs than a steam locomotive and such vehicles can, if desired, be kept in service for 95% or more.
Diesel Locomotive: -
- It is available for hauling for about 90% of its working days.
Steam locomotive: -
- It is available for hauling work for about 60% of its working days, the remaining 40% is spent in preparing for service, maintenance, and overhaul.
9. The horsepower of steam locomotives is
A. up to 1500
B. 1500 to 2000
C. 2000 to 3000
D. 3000 to 4000
Answer: A. up to 1500
Explanation:
- The range of horsepower of diesel locomotive is 1500 – 2500
- The maximum rating of a steam locomotive is around 1500
- Electric AC power locomotives are rated at up to 6600 hp
10. The overall efficiency of steam locomotive is around
A. 5 to 10 percent
B. 15 to 20 percent
C. 25 to 35. percent
D. 35 to 45 percent
Answer: A. 5 to 10 percent
Explanation:
- The overall efficiency of a typical steam locomotive was no more than 5% to 10%.
- The overall efficiency of the diesel locomotive is 20 to 25 percent.
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