How the train run and is it true that A/c. in train works on power gets thru running wheels.?

Question

means there is no need of extra electricity from over head wire

Answer 1

Power for Aircon is usually provided from the Locomotive through jumper cables to each coach or carriage.

Older coaches used Dynamos driven by the wheels to charge the batteries and power their lights but there was not enough power to run aircon or pressure ventilation with this system.

The Track is used for a return path for overhead wire power collection or for 3 rd rail power collection, but not for 4th Rail power where feed and return are both seperate to the running rails.  The track also carries a low voltage on non electrified lines to work what are called track circuits which indicate to signalmen where trains are in real time.

Answer 2

Running the aircon from the coach wheels WOULD put an extra load on overhead wires, it would make effectively make the train heavier or more resistant to movement since the carriage wheels then have to turn the aircon pumps.  You don't get anything for nothing, particularly when it comes to energy.  

Also every time the train stops the aircon would stop too.  Since windows cannot be opened in aircon carriages, they would soon get too hot inside in sunny weather.  

Diesel hauled passenger trains usually have a power car which contains another Diesel engine running an alternator which powers the train lighting and aircon.  That way you can connect any suitable locomotive to the train set, even a steam one.

Before carriages were air conditioned, they usually ran small generators attached to the axles which charged batteries for train lighting.  Since the batteries were usually close to fully charged all the time, the generators put only a small extra load on the train as a whole.  

Some old carriages were heated by coal stoves which generated steam which was circulated around the carriage, just as in a house.  The early "Orient Express" carriages used this system.

Answer 3

Third rail is perfect for mass transit systems.

You don't need high-speed overhead catenary when all the stations are closely-spaced together (less than 1 mile apart is typical for subway or commuter systems) where a train has no opportunity or need to accelerate to 100mph+.

In subway systems, it costs more to dig tall tunnels to accomodate overhead catenary, which is another reason why a 3rd rail power system is preferred here.

A solid third rail is also less fragile than catenary.

All of that indicates why it doesn't make sense to retrofit 3rd-rail commuter systems for overhead.

The majority of subway systems in the U.S. and Canada, new or old, are 3rd-rail-powered for all these reasons.

Answer 4

trains get pulled by the engines at the starting piont . it is true that A/c run from electicity generated by wheels while the train is running.

at main stations they run A/c by elecricity from station.

it is not possible to run train without getting power from over head wires. because the motors, which pull the train need high quantity of electricity.

the electricity generated by wheels are not enough to pull the train, those r sufficent only for lights, fans, A/c's etc ;

if we try to generate electricity to pull train by wheels, there will  be added friction to movemet of trains, thus minimising the train speed.

so, electricity from a moving  fast moving train to pull itself = (results in) more friction = less speed of train = less electricity generated = still less speed . so ultimatly the fast train stops.

and according to a theory (i forgot its exact name) an object can't move itself by generating energy itself.

Answer 5

Third rail is hot.

Answer 6

Diesel trains have diesel engines running electric motors. The motors are AC. This way there is no need for big bulky transmission.

Answer 7

Power through a third rail is DC and at a much lower voltage than the AC obtained from overhead cables (about 650volts as opposed to 25,000). Numerous substations are required and trains cannot run as fast as those drawing power from the overhead. Here in the UK much of the former Southern Railway ( most of the lines to the south and east of London) were electrified on the 3rd rail basis. This meant that whilst an intense service could be run, speeds were and are not very high (c60mph average). Whilst it was possible a couple of years ago to run a special record attempt from London to Brighton on this system which touched 100 mph at times and did the journey in about 33 minutes, the average time for fast trains on the route (about 55 miles) is 50-55 minutes. The high speed  Eurostar trains from London to Paris via the Channel Tunnel would travel at 125mph from Paris and through the tunnel, but slowed to 60 when they had to use the third rail network - hence the reason to build a totally new line, the High Speed Rail Link which uses the overhead system

Later. I should add, particularly in view of the last answer, that,  here in the UK all electrification of suburban/mass transit lines sine the 1940s has been on the overhead system, starting with the ex-Great Eastern lines to Shenfield and Southend out of Liverpool Street, the Bedford -St Pancras electrification and  that of the suburban lines out of Kings Cross and, of course, not forgetting the electrification of the Glasgow suburban services. Quite apart from avoiding the problems of icing of the conductor rails mentioned in another answer (and, of course, ice can form on the overhead and affect that), it permits power to be taken direct from the National Grid system, rather than having the expense of building power stations  and far more sub-stations. This has meant that trains which travel from north of London to the south - e.g. those travelling on the former Thameslink services - have to be dual powered with both the abilty to collect current from the overhead via pantographs and from the third rail by collector shoes. These trains can be seen changing from one method to the other at Farringdon station.

Answer 8

An electrical circuit needs 2 connections.  That's why every power cord has at least 2 prongs, right?  

For a train, one "prong" is the overhead wire.   The other "prong" is the steel rails of the track.

You also know in electrical circuits, one side is "hot" and the other is "neutral" or "ground".   The overhead wire is "hot", and both rails are "ground" for obvious reasons.

Why don't they do like on model trains, where one rail is hot and the other ground?  Because real trains need way too much power, there'd be no practical way to insulate switches, for instance.   Also, real trains have solid metal axles, and there's no practical way to insulate them. It would also present a nasty electrocution hazard for anyone on the ground, given the very high voltages involved. (600 VDC to 33,000 VAC).

Answer 9

As the correspondent above mentions the third rail system has disadvantages. Additional problems are icing and leaves in Autumn which cause problems with the electrical path. Its only used because the system has been around for years and saves the capital costs in retrofitting overhead wires. The old Southern Railway used a lesser clearance from tunnel walls etc. and this may present problems with the space needed for overhead systems.

Answer 10

I'm not too familiar with this but indeed, there is a third "hot" rail where the eletricity is picked up via "shoes" on the locomotive/power car.  I think third-rail is typically used on mass transit/commuter operations (a number of agencies use them in the U.S., Asia, and Europe) and is supplied via direct current although alternating current may be gaining favor now because of its advantages (although I'm unsure).