SNCF Class BB 20004
| Company type | Locomotive |
|---|---|
| Industry | Railway transport |
| Predecessor | BB16540 |
| Founded | 1959 |
| Fate | Reverted to original setup and designation in 1969 |
| Products | Dual-voltage electric locomotive |
| Owner | SNCF |
The SNCF class BB 20004 was a dual-voltage experimental locomotive, reconstructed from the damaged BB16540 in 1959. Following the conclusion of its testing phase in 1969, it was reverted to its original setup and designation.
History
During the 1950s, SNCF conducted trials with three dual-voltage locomotives converted from DC-only models. These units delivered full output exclusively under 25 kV AC, while their performance under 1.5 kV DC was restricted to roughly 10%. This limited DC capability sufficed for specific routes such as Aix-les-Bains to Annecy, where low DC power was mainly required for accessing stations or moving within depots.
By the end of the 1950s, SNCF introduced the BB8500 and BB17000 series, which were procured in configurations for DC-only, AC-only, and dual-voltage operations. The dual-voltage version, designated BB25500, was launched in the early 1960s as part of this series.
In pursuit of a more efficient dual-voltage locomotive, SNCF transformed the damaged BB16540 into the BB20004 prototype in 1959.
Prototype for later designs
Contrary to earlier dual-voltage units with limited capabilities, BB20004 incorporated both AC and auxiliary DC equipment that allowed it to function under both electrical systems with enhanced power regulation. Although frequently regarded as the forerunner of the BB25500 locomotives, the latter were mainly derived from the BB16500 series and included parts either adapted from older models or newly engineered.
BB20004 played a crucial role in advancing SNCF’s expertise in dual-voltage technology and contributed significantly to the design evolution of the BB25500 class and subsequent dual-voltage locomotive generations.