Train lighting is one of the important passenger amenities which influence the image of Railways. Although the first train ran on 16th April 1853, train lighting system came to Indian Railway in 1930 through axle driven Dynamo pioneered by Ms. J. Stones & co.Power supply system for trains is designed and developed to suit the requirement of AC and non-AC working in the trains. Few factors considered for development of such systems are as under.
- Coach load
- Speed of the train
- Weight of the equipment
- Available technology for reliable equipment etc
- Axle driven system working on 24V DC
- Axle driven system working on 110V DC
- MOG with 415V, 3 phase generation, and 110V AC utilization
- EOG with 415V,3 phase generation, and 110V AC utilization
- EOG with 750V, 3 phase generation and 415 & 110V AC utilization
Power feeding from OHE for lighting loads (EMUS):
- 750V DC –light & fan works on 110V DC
- 1500V DC – light & fan works on 110 VAC
- 25 KV—light & fan works on 141 VAC
Power feeding from HOG for Hotel Loads (Loco):
- Hotel load power is taken from Electric/Diesel Locomotive.
- Hotel load power supply taken directly from OHE through a separate pantograph mounted on the power car.
Self Generation system:
The power supply arrangement of SG coach has underslung alternator, which is driven by the running axles of the coach with the belt of the coach. The voltage of the alternator which varies with the speed of the train is regulated with the help of RRU and converted to 110 v DC and is used for charging the battery. The electrical load of the coach is supplied through the 110 v DC battery at the halt.
- The system is independent of the mode of traction.
- As each coach has a battery, so no additional source is required.
- The problem/defect in any particular coach does not affect the others.
- The system can be designed to suit its specific requirement.
- It gives better flexibility in rake formation majority of SG type coach is more.
- The electrical load of the coach is restricted by the limitation of the capacity of generation i.e. 2*25 kw per coach at present.
- The power is not generated during standing or slow movement of the train, therefore bulky batteries are provided.
- There is no standby source for alternator and batteries, so system became poor reliability.
- The system requires the extensive maintenance of alternator, batteries, belts, tensioning device etc.
- The system has the very poor efficiency of 57%for power it receives from the locomotive.
The EOG system is used in Rajdhani and Shatabdi type trains which have only AC coaches and have large power requirement. Each EOG train has 2 power cars with 2*250kw alternator each. The power is fed by any two DA sets through IVC. The power is supplied at 3 phase, 750V, which is stepped down in an individual coach to 3 phase,415v for supplying various loads like RMPU, WRA etc. The 110v AC supply for lights and fans is obtained by further stepping down the 415v supply. A 24v battery is used for supplying a few emergency lights provided in the coach.
- With the development of high capacity power cars, 2*336 kw power is available from each power car.
- The system does not require the use of bulky batteries and alternators in individual coaches.
- The system has higher reliability due to standby DA sets and reduced number of equipment.
- Due to an elimination of heavy equipment, the dead weight of the coach is reduced.
- The system is independent of the type of traction i.e. diesel or electric locomotive.
- The system has better energy efficiency as compared to the self-generating system.
- Low maintenance.
- The cost of energy is high due to fuel cost.
- Even with 750V, 3 phase, there is still an effect of voltage drop at the farthest end of the train.
- Noise and smoke pollution are generated from power cars.
- The passenger carrying capacity of the train is reduced due to provision of power car
The MOG system was adopted by IR for slow-moving passenger trains which have the very low generation to non-generation ratio. These trains had one power car in the middle of the train, which fed power supply to the coaches at either side of power car. The power car coach had two DA set of 30 KVA each out of which one was used as standby. The power car coach also had one 3 phase, 30 KVA step down transformer of 415/110 v. The 110 v AC supplied to the coaches through couplers.The system was discontinued after the introduction of EMU and DMU service.
The system was most suitable for slow-moving branch line passenger trains. Light and fan of all the coaches had centralized control in power car coach. Fan and lights were working on AC supply. There was no need for standby batteries in the coaches.
- There were noise and smoke; pollution due to DA set working.
- The operator was required to power car coach.
- Some valuable passenger spaces were occupied by DA sets.
The HOG scheme is widely used power supply by Railways world over. The power supply system for the coaches is either received from the locomotive or it is directly tapped from traction overhead lines into the power cars.The system is considered to provide cost-effective, reliable and energy efficient supply system for coaches.
The HOG scheme can be considered with following two options.Hotel load power is taken from Electric/Diesel Locomotive.Hotel load power supply taken directly from OHE through a separate pantograph mounted on the power car.The second system is not considered technically feasible for Indian Railways due to some limitations.HOG scheme where power is taken from Electric/Diesel Locomotive:
The power supply is received directly from locomotive through couplers. The supply from locomotive can be a 750v, 3 phase supply or a single phase supply received from loco is regulated and stepped down in individual AC coaches, with the help of converters to provide a regulated 415 v, 3 phase supply. Similarly, in AC coaches, power supply from locomotive can be stepped down and regulated to provide single phase, 110 v AC supplies. One power car with standby DA sets is also used in the train, which can supply power to the coaches in case of failure of a locomotive.
- Cheaper cost of power as compared to EOG & SG system.
- Pollution is less as compared to EOG system.
- One power car may be replaced by trailer coach, revenue increased.
- Escorting staff will be reduced to one power car.
- The net dead weight of the train is reduced as compared to SG system.
- HOG type AC coaches can be used in EOG type trains.
- This system is compatible with diesel and electric traction.
- Maintenance cost of HOG system coaches is lower as compared to SG coaches
While working with electric locomotive there are power interruptions for short durations to various electrical equipment except for lights while through the neutral section. One power car is still required for supplying power during failure of OHE supply or locomotive etc.HOG type coaches require rake integrity of coaches similar to EOG system.