11. In tramways which of the following motors is used?
A. D.C. shunt motor
B. D.C. series motor
C. A.C. three phase motor
D. A.C. single phase capacitor start motor
Answer: B. D.C. series motor
Explanation:
- In trains or bus, there are many compartments full of passengers & luggage, so during the starting, it requires high starting torque.
- DC series motor is used for the locomotive because it has very high starting torque and variable speed.
- DC series motors will have a starting torque as high as 500% compared to the normal operating torque.
- The DC series motor has long been the most common type of traction motor for railroad service in both electric and diesel-electric locomotives because of its superior operating characteristics.
- As the load on the motor increases, the field strength automatically increases, and the result is an increase in torque with a decrease in speed.
- Conversely, the speed increases as the load decreases.
- Consequently, the series motor tends to adjust itself readily to the varying tractive effort required to accelerate and power a train.
12. In a steam locomotive electric power is provided through
A. overhead wire
B. battery system
C. small turbogenerator
D. diesel engine generator
Answer: C. small turbogenerator
Explanation:
- A turbo generator is an electric generator connected to the shaft of a steam turbine or gas turbine for the generation of electric power.
- When operating, these generators would run around 2400 RPM and generate 32 to 37 volts DC. They would have a 350-to-500-Watt capacity.
Important Information
System of traction systems used in India are:
Non-electric traction system:
- Traction system develops the necessary propelling torque, which do not involve the use of electrical energy at any stage to drive the traction vehicle known as electric traction system.
- Example: Direct steam engine locomotive, direct diesel engine locomotive.
Electric traction system:
- Traction system develops the necessary propelling torque, which involves the use of electrical energy at any stage to drive the traction vehicle, known as electric traction system.
- Example: Diesel electric locomotives, electric locomotives.
13. Which of the following drives is suitable for mines where explosive gas exists?
A. Steam engine
B. Diesel engine
C. Battery locomotive
D. Any of the above
Answer: C. Battery locomotive
Explanation:
- A battery engine drive is the most suitable drive for mines where explosive gases exist. Because,
- The modern battery uses advanced switching power supply technology which not only improves charging efficiency but also does not produce any harmful gases while other drives such as petrol or diesel do.
- Petrol, diesel, or steam are flammable fuels and catch fire easily, hence it is not safer.
- The running cost of petrol, diesel, or steam mines is higher as compared to battery engine drives.
14. In case of locomotives the tractive power is provided by
A. single cylinder double acting steam engine
B. double cylinder, single acting steam engine
C. double cylinder, double acting steam engine
D. single stage steam turbine
Answer: C. double cylinder, double acting steam engine
Explanation:
- The force which a locomotive can exert when pulling a train is called its tractive effort and depends on various factors.
- Tractive effort is defined as the force at the rims or the outer edges of the driving wheels of moving trains.
- In other words, it is the sum of the tractive force and rolling effort on the road surface. In the main line train, tractive effort is caused by the locomotive, and in a suburban train, it is caused by motor coaches.
- The draw pull bar force is the horizontal force available for the vehicles for pulling the load.
- This force is less than the tractive effort required to move the locomotive.
- The maximum allowable tractive effort that can be applied without wheel slip.
- In case of locomotives the tractive power is provided by double cylinder, double acting steam engine.
15. Overload capacity of diesel engines is usually restricted to
A. 2 percent
B. 10 percent
C. 20 percent
D. 40 percent
Answer: B. 10 percent
Explanation:
- The diesel cycle is known as a “constant pressure cycle” which depends on high compression to ignite the fuel, no spark ignition involved.
- As the compression in the cylinder increases, the gases in the cylinder heat up and diesel fuel is injected starting the combustion. Since the fuel is sprayed in droplets, not all of it is burned at once.
- As the fuel atomizes between the drops it combusts until all the droplets are reduced in size and used up.
- This burning of fuel is hopefully complete by the time the piston is at the bottom of the stroke.
- This slower burning of diesel fuel gives a constant force on the piston, hence – “constant torque” as opposed to the explosive spark ignition of a gasoline (Otto cycle) engine.
- Therefore, the horsepower of the diesel engine locomotive remained constant at all speeds.
- Due to constant kW output prime mover, the overload capacity of diesel locomotive is low. Even an overload of 15% may stall the engine.
16. In case of steam engines, the steam pressure is
A. 1 to 4 kgf/cm2
B. 5 to 8 kgf/cm2
C. 10 to 15 kgf/cm2
D. 25 to 35 kgf/cm2
Answer: C. 10 to 15 kgf/cm2
Explanation:
- The pressure of steam in a locomotive is 10-15 kg/cm2 or around 200 to 250 psi (1.38 to 1.72 MPa).
- In the later year, high pressure steam locomotive was introduced which operates at 350 psi (2.41 MPa).
- The high-pressure steam in locomotive increases the efficiency of a heat engine.
17. The steam engine provided on steam locomotives is
A. single acting condensing type
B. single acting non-condensing type
C. double acting condensing type
D. double acting non-condensing type
Answer: D. double acting non-condensing type
Explanation:
- The steam engine is an external combustion engine in which steam is used as the working substance to convert the heat energy of steam into mechanical work.
- A steam engine is a reciprocating type of engine. In a steam engine, steam at high pressure and temperature is expanded to move the piston.
- The reciprocating motion of the piston is converted into rotary motion by a slider-crank mechanism.
Classification of Steam Engine
Steam engines may be classified according to different criteria, as follows:
The orientation of the axis of the cylinder:
- Vertical
- Horizontal
- Inclined.
The direction of steam inlet:
- Single-acting: – In single-acting endues the steam is supplied on one side of the piston only. Thus, we get one power stroke and one idle stroke in each cycle.
- Double-acting: - In double-acting engines steam is supplied on one side of the piston during forward smoke and on its other side during the return stroke. Thus, we get two power strokes in each cycle.
Number of cylinders:
- Simple steam engine: - In a simple steam engine the steam expands in one cylinder only
- Compound steam engine: - In the compound cylinder, steam is allowed to expand partly in one cylinder, and partly in second or third cylinders.
The exhaust of steam:
- Condensing: - In condensing engines, the steam coming out of the cylinder, after expansion, is sent to an enclosed chamber called a condenser. Inside the condenser, pressure is maintained below atmospheric pressure. Here, the steam is condensed by cooling water.
- Non-condensing: - In non-condensing engines, the steam is exhausted directly to the atmosphere. Condensing engines are more efficient, as more work output is obtained from the steam. e.g steam locomotive and steam wagon.
Application:
- Stationary: -Stationary engines are used in plants for the generation of mechanical or electrical power, and to drive pumps, shafts, machines, etc.
- Locomotive: - Locomotive engines are used in railroad applications.
- Marine: - Marine engines are used in ships.
Speed:
- Low speed below 100 rpm
- Medium speed—100 to 300 rpm
- High speed above 300 rpm
Since it is difficult to install a condenser on a locomotive, the steam engine runs non-condensing and, therefore, has a very low thermal efficiency of about 6-8 percent. it has strictly limited overload capacity.
18. Electric locomotives in India are manufactured at
A. Jamalpur
B. Bangalore
C. Chittranjan
D. Gorakhpur
Answer: C. Chittranjan
Explanation:
- Chittaranjan Locomotive Works is a state-owned electric locomotive manufacturer based in India.
- It is located at Chittaranjan in Asansol.
- It is one of the largest locomotive manufacturers in the world.
- Chittaranjan Locomotive Works has supplied many types of locomotives.
19. The wheels of a train, engine as well as bogies, are slightly tapered to
A. reduce friction
B. increase friction
C. facilitate braking
D. facilitate in taking turns
Answer: D. facilitate in taking turns
Explanation:
The wheels of a train, engine as well as bogies, are slightly tapered to facilitate in taking turns
20. Automatic signaling is used for which of the following trains?
A. Mail and express trains
B. Superfast trains
C. Suburban and Urban electric trains-
D. All trains
Answer: B. Superfast trains
Explanation:
When a Driver finds an Automatic Stop signal with an 'A' marker at 'On', he shall bring his train to a stop in the rear of the signal.More Objective Questions in Electrical Traction