Dynamic braking

In physical sciences, mechanical energy is the sum of potential energy and kinetic energy. The principle of conservation of mechanical energy states that if an isolated system is subject only to conservative forces, then the mechanical energy is constant. If an object moves in the opposite direction of a conservative net force, the potential energy will increase; and if the speed of the object changes, the kinetic energy of the object also changes. In all real systems, however, nonconservative forces, such as frictional forces, will be present, but if they are of negligible magnitude, the mechanical energy changes little and its conservation is a useful approximation. In elastic collisions, the kinetic energy is conserved, but in inelastic collisions some mechanical energy may be converted into thermal energy. The equivalence between lost mechanical energy and an increase in temperature was discovered by James Prescott Joule.

In electrical engineering, the armature is the winding of an electric machine which carries alternating current. The armature windings conduct AC even on DC machines, due to the commutator action or due to electronic commutation, as in brushless DC motors. The armature can be on either the rotor or the stator, depending on the type of electric machine.

An electric generator or electric motor consists of a rotor spinning in a magnetic field. The magnetic field may be produced by permanent magnets or by field coils. In the case of a machine with field coils, a current must flow in the coils to generate the field, otherwise no power is transferred to or from the rotor. The process of generating a magnetic field by means of an electric current is called excitation. Field coils yield the most flexible form of magnetic flux regulation and de-regulation, but at the expense of a flow of electric current. Hybrid topologies exist, which incorporate both permanent magnets and field coils in the same configuration. The flexible excitation of a rotating electrical machine is employed by either brushless excitation techniques or by the injection of current by carbon brushes.

Regenerative braking is an energy recovery mechanism that slows down a moving vehicle or object by converting its kinetic energy into a form that can be either used immediately or stored until needed. In this mechanism, the electric traction motor uses the vehicle's momentum to recover energy that would otherwise be lost to the brake discs as heat. This method contrasts with conventional braking systems. In those systems, the excess kinetic energy is converted to unwanted and wasted heat due to friction in the brakes, or with rheostatic brakes, where the energy is recovered by using electric motors as generators but is immediately dissipated as heat in resistors. In addition to improving the overall efficiency of the vehicle, regeneration can significantly extend the life of the braking system as the mechanical parts will not wear out quickly.

The Canadian Pacific Railway, also known simply as CPR or Canadian Pacific and formerly as CP Rail (1968–1996), is a Canadian Class I railway incorporated in 1881. The railway is owned by Canadian Pacific Railway Limited, which began operations as legal owner in a corporate restructuring in 2001.

BNSF Railway is one of the largest freight railroads in North America. One of seven North American Class I railroads, BNSF has 35,000 employees, 32,500 miles (52,300 km) of track in 28 states, and nearly 8,000 locomotives. It has three transcontinental routes that provide rail connections between the western and eastern United States. BNSF trains traveled over 169 million miles in 2010, more than any other North American railroad.

The Kansas City Southern Railway Company is an American Class I railroad. Founded in 1887, it operates in 10 Midwestern and Southeastern U.S. states: Illinois, Missouri, Kansas, Oklahoma, Arkansas, Tennessee, Alabama, Mississippi, Louisiana and Texas. KCS has the shortest north-south rail route between Kansas City, Missouri, and several key ports along the Gulf of Mexico.

The Union Pacific Railroad, legally Union Pacific Railroad Company and often called simply Union Pacific, is a freight-hauling railroad that operates 8,300 locomotives over 32,200 miles (51,800 km) routes in 23 U.S. states west of Chicago and New Orleans. Union Pacific is the second largest railroad in the United States after BNSF, with which it shares a duopoly on transcontinental freight rail lines in the Western, Midwestern and West South Central United States.

In rail transport, head-end power (HEP), also known as electric train supply (ETS), is the electrical power distribution system on a passenger train. The power source, usually a locomotive at the front or 'head' of a train, provides the electricity used for heating, lighting, electrical and other 'hotel' needs. The maritime equivalent is hotel electric power. A successful attempt by the London, Brighton and South Coast Railway in October 1881 to light the passenger cars on the London to Brighton route heralded the beginning of using electricity to light trains in the world.

Connex South Eastern was a train operating company in the United Kingdom owned by Connex that operated the South Eastern franchise from October 1996 until November 2003.

The British Rail Class 466 Networker are a fleet of 43 electric multiple units that were built by Metro-Cammell in 1993 and 1994. The units are currently operated by Southeastern.

An electric multiple unit or EMU is a multiple-unit train consisting of self-propelled carriages using electricity as the motive power. An EMU requires no separate locomotive, as electric traction motors are incorporated within one or a number of the carriages. An EMU is usually formed of two or more semi-permanently coupled carriages, but electrically powered single-unit railcars are also generally classed as EMUs. The great majority of EMUs are passenger trains, but versions also exist for carrying mail.

Blackfriars, also known as London Blackfriars, is a central London railway station and connected London Underground station in the City of London. It provides Thameslink services: local, and regional and limited Southeastern commuter services to South East London and Kent. Its platforms span the River Thames, the only one in London to do so, along the length of Blackfriars Railway Bridge, a short distance downstream from Blackfriars Bridge. There are two station entrances either side of the Thames, along with a connection to the London Underground District and Circle lines.

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.

A torque converter is a type of fluid coupling that transfers rotating power from a prime mover, like an internal combustion engine, to a rotating driven load. In a vehicle with an automatic transmission, the torque converter connects the power source to the load. It is usually located between the engine's flexplate and the transmission. The equivalent location in a manual transmission would be the mechanical clutch.

A fluid coupling or hydraulic coupling is a hydrodynamic or 'hydrokinetic' device used to transmit rotating mechanical power. It has been used in automobile transmissions as an alternative to a mechanical clutch. It also has widespread application in marine and industrial machine drives, where variable speed operation and controlled start-up without shock loading of the power transmission system is essential.

A retarder is a device used to augment or replace some of the functions of primary friction-based braking systems, usually on heavy vehicles. Retarders serve to slow vehicles, or maintain a steady speed while traveling down a hill, and help prevent the vehicle from "running away" by accelerating down the hill. They are not usually capable of bringing vehicles to a standstill, as their effectiveness diminishes as vehicle speed lowers. They are usually used as an additional "assistance" to slow vehicles, with the final braking done by a conventional friction braking system. As the friction brake will be used less, particularly at higher speeds, their service life is increased, and since in those vehicles the brakes are air-actuated, it helps to conserve air pressure too.

A water brake is a type of fluid coupling used to absorb mechanical energy and usually consists of a turbine or propeller mounted in an enclosure filled with water.

A hydraulic fluid or hydraulic liquid is the medium by which power is transferred in hydraulic machinery. Common hydraulic fluids are based on mineral oil or water. Examples of equipment that might use hydraulic fluids are excavators and backhoes, hydraulic brakes, power steering systems, automatic transmissions, garbage trucks, aircraft flight control systems, lifts, and industrial machinery.

Radiators are heat exchangers used for cooling internal combustion engines, mainly in automobiles but also in piston-engined aircraft, railway locomotives, motorcycles, stationary generating plant or any similar use of such an engine.