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6. Current in the rails
Whatever the type of traction current distribution, catenary or lateral conductor, the current returns via the running rails. The empirical formula R v = 0.9/p gives the linear resistance R v as a function of rail weight per metre. For a standard track with a 60 kg/m rail, R v ≍ 0.015 Ω/km. There are two cases to consider, depending on the nature of the current to be conveyed.
In direct current, the high currents absorbed by prime movers generate significant voltage drops.
for I = 4,000 A ; ΔU = rI = 0.015 × 4,000 = 60 V/km ;
i.e. for 10 km: ΔU = 800 V.
This voltage drop is reduced, by approximately...
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Current in the rails
Special case: the trolleybus
Bibliography
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Alstom Transport http://www.alstom.fr
Bombardier Transportation http://www.bombardier.com/fr/transport
Standards and norms
- Spécification technique concernant la fourniture de fils rainurés pour lignes de contact - UIC 870 - 01-56
- Railway applications – Traction network supply voltages - NF EN 50163/A1 - 10-07
- Railway applications – Rolling stock – Pantographs: characteristics and tests – Part 2: Pantographs for metros and streetcars - NF EN 50206-2 - 03-11
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