The Electric engine

How it works

An electric engine is technically very straight foreword, it picks up electricity either by means of an overhead power supply or electric rails, has an onboard transformer which brings the power supply down to an acceptable level (like a sub-station on wheels). There is also a section that regulates the power supply to a level controlled by the driver. Then the power is provided to the traction motors on each axle of the engine's wheels, which is what provides the forward thrust.

Advantages of Electric engines:

All that is needed is power transformers and regulators, so the engine is very light. Traction motors weigh relatively very little. This is very useful because it means the track doesn't get worn out so fast, and they can travel at much higher speeds.

Also electric engines are very powerful, electric motors can produce as much torque as you give them power, and because the power supply to the motors is not limited in theory any power is possible. In Diesels the power supply to the motors is always limited by the amount of electricity the diesel engine can generate. In practice infinite power is not possible, structural integrity would not be able to hold up.

Another major advantage is speed. Electric engines have almost no moving parts, just the motors and the wheel axles. Diesels have a very large number of moving parts involving many pistons, valves, turbines, chains etc. and this is very noticeable the speed record for an electric engine is 320 mph, for a diesel its only 148 mph. In theory an electric engine has no top speed, although it is given a design speed for which the manufacturers consider to be its top speed if it is to be kept running in good condition.

Electric engines are also very efficient. They are quiet and don't produce a lot of heat so most of the energy is being converted into foreword motion. However this might not be so straight foreword given the fact that power stations required to generate electricity do not do so at full efficiency. They are still more efficient than diesels after considering the power station stage although the efficiency is not so greatly different than actually apparent.

Disadvantages of Electric engines:

The primary disadvantage of electric engines is that they require a power supply, usually provided by overhead lines. As most major railways in most countries were built in the steam era, no power lines were not built. So if electric engines are to run then the line must be electrified where power lines are built above the railway. This can be a very expensive task as it may involve raising the height of bridges and tunnels as well as the huge cost of building suspended lines over many miles of track. This is why only important mainlines are electrified. So electric engines are limited, they cannot travel everywhere on the rail network.

The other much more minor disadvantage is the possibility of power disruption. In order to work a pentograph on top of the locomotive must make contact with the electric wires properly at all times, sometimes it is possible for things to go wrong. Also should any engineering work be performed on the railway line the electricity supply has to be shut down meaning other trains cannot pass through, and on busy railways this can cause problems as a large numbers of trains have to be re-routed or sometimes part of the journey has to be done by bus.