Multiple-unit train control
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Multiple-unit train control |
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Multiple-unit train control, sometimes referred to simply as multiple-unit or MU, is a method of simultaneously controlling all the traction equipment in a train, whether it be a number of self-powered cars or a set of locomotives, from a single location.
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[edit] Origins
The system was pioneered by Frank Sprague and tested on the South Side Elevated Railroad (now part of the Chicago 'L') in 1897. Sprague also designed the first practical trolley car in the United States of America.
MU operation solved a problem in the control of street cars and rapid transit cars, where trains were made up of individually self-powered cars, or a combination of self-powered and unpowered cars (trailers). The problem involved not only the issue of transmitting control signals between cars, but also of making certain that the motors in all the cars operated in the same fashion and responded simultaneously to changes in the control signals issuing from the operator's position.
[edit] Locomotive applications
- Main article: Multiple working
Sprague's MU system was adopted for use by diesel-electric locomotives in the 1920s, however these early 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. Most modern diesel locomotives are now delivered equipped for MU operation, allowing a consist (set) of locomotives to be operated from one cab, thereby eliminating the need for a train crew in each engine (something steam locomotives necessitated). However, not all MU connections are standardized between manufacturers, limiting the types of locomotives that can be used together. In North America there is a high level of standardization, using the Association of American Railroads system [1].
Modern locomotive MU systems can be easily spotted due to the large MU Cables to the right and left of the coupler. The connections typically consist of several air hoses for controlling the air brake 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.
Locomotives set up to use slugs have extra connections for transmitting electricity from the diesel electric generator on the "mother" unit to the traction motors on the slug.
[edit] Passenger train applications
Modern Electric Multiple Unit and Diesel Multiple Unit vehicles often utilise a specialised coupler that provides both 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 Scharfenberg coupler, various knuckle hybrids (such as the Tightlock, used in the UK), the Wedgelock coupling, Dellner couplings (similar to Scharfenberg couplers in appearance), and the BSI coupling.
A second adoption of MU technology is Push-Pull trains operating with a standard locomotive at one end only. Control signals are either received from the cab as normal, or from a cab car at the other end that is connected to the locomotive by MU cables through the intermediate cars.
[edit] References
[edit] See also
- Air brake (rail)
- Railway brakes
- Diesel locomotive
- Push-pull (mode of operation for locomotive-hauled trains)
