Multiple-unit train control

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Multiple-unit train control, sometimes abbreviated to multiple-unit or MU, is a method of simultaneously controlling all the traction equipment in a

passenger cars or a set of locomotives—with only a control signal transmitted to each unit. This contrasts with arrangements where electric motors in different units are connected directly to the power supply switched by a single control mechanism, thus requiring the full traction power to be transmitted through the train.

A set of vehicles under multiple unit control is referred to as a

Origins

Multiple unit train control was first used in electric multiple units in the 1890s.

The Liverpool Overhead Railway

The Liverpool Overhead Railway opened in 1893 with two-car electric multiple units,^[2] controllers in cabs at both ends directly controlling the traction current to motors on both cars.^[3]

Frank J. Sprague

The multiple unit traction control system was developed by

) in 1897. In 1895, derived from his company's invention and production of direct current elevator control systems, Frank Sprague invented a multiple unit controller for electric train operation. This accelerated the construction of electric traction railways and trolley systems worldwide. Each car of the train has its own traction motors: by means of motor control relays in each car energized by train-line wires from the front car all of the traction motors in the train are controlled in unison.

Locomotive applications

Sprague's MU system was adopted for use by

in the 1920s; however, these early control connections were entirely pneumatic. Today's modern MU control utilizes both pneumatic elements for brake control and electric elements for throttle setting, dynamic braking, and fault lights.

In the early days of diesel electric MUing there were numerous systems; some were compatible with one another, but others were not. For example, when first delivered, many

B units

, a train would require two train crews as the four A units could not be multiple-unit-controlled, except as two groups of two.

Terms used in North America are A unit and B unit where the B or "booster" unit does not have a control cab; slug where the B unit has traction motors powered by the "mother" unit via extra connections; and cow-calf for switcher locomotive units. A control car remote control locomotive has remote control but not traction equipment.

Most modern diesel locomotives are now delivered equipped for MU operation, allowing a consist (set) of locomotives to be operated from one cab. Not all MU connections are standardized between manufacturers, thus limiting the types of locomotives that can be used together. However, in North America there is a high level of standardization between all railroads and manufacturers using the Association of American Railroads (AAR) system which allows any modern locomotive in North America to be connected to any other modern North American locomotive.^[4] In the United Kingdom several incompatible MU systems are in use (and some locomotive classes were never fitted for MU working), but more modern diesel locomotives used on British railways use the standard Association of American Railroads system.

Modern locomotive MU systems can be easily spotted due to the large MU cables to the right and left of the

system, and an electrical cable for the control of the traction equipment. The largest hose, located next to the coupler, is the main air brake line or "train line". Additional hoses link the air compressors on the locomotives and control the brakes on the locomotives independently of the rest of the train. There are sometimes additional hoses that control the application of sand to the rails.

With distributed power, long trains, e.g. ore trains on mining lines, may have locomotives at each end and at intermediate locations in the train to reduce the maximum drawbar load. The locomotives are often radio-controlled from the lead locomotive by the Locotrol system. Remote control locomotives, e.g. "switchers" in hump yards, may be controlled by a stationary operator. These types of remote control systems often use the AAR MU standard which allows any locomotive using the AAR MU standard to be easily "MU'ed" to a control receiver and thus capable of becoming remote-controlled.

Passenger train applications

Modern electric multiple unit and diesel multiple unit vehicles often utilise a specialised coupler that provides mechanical, electrical and pneumatic connections between vehicles. These couplers permit trains to be connected and disconnected automatically without the need for human intervention on the ground.

There are a few designs of fully automatic couplers in use worldwide, including the

.

Multiple control technology is also used in

at the other end that is connected to the locomotive by cables through the intermediate cars.

In the United States,

Northeast corridor

with only one operator.

In trolleybuses

In the

So the invention by Veklich was borrowed by many trolleybus companies, in particular, Donetsk, Kherson, Nikolaev, Minsk, Tallinn, Riga, Leningrad (now St. Petersburg), Novosibirsk and many other cities.

The design of the rotating joint was similar to that of a tram with rods and hinges; both trolleybuses would have their motors and brakes controlled by the driver in the front.[5] They also allowed for coupling and decoupling in 3–5 minutes, which was intended such that at the end of peak hours, the trolleybuses could be split again into two. However, due to the abundance of trolleybuses and electricity, there was rarely a need to do so.^[5]

With the retirement of the MTB-82 trolleybuses, the system was also adapted to the Skoda 9Tr and the

Throughout its use, the implementation of trolleybus trains have been used in

See also

References

External links

• Frank Sprague
• The Evolution of the Diesel Locomotive in the United States