The Indian locomotive class WDG-5 (EMD GT50AC) is a class of heavy haul Diesel–electric locomotive built by Banaras Locomotive Works, Varanasi in collaboration with Electro-Motive Diesel. At a rated power output of 5,500 horsepower (4,100 kW), it is the second most powerful diesel locomotive class on Indian Railways, just out-powered by the 6,000 horsepower (4,500 kW) WDG-6G. Derived from the EMD SD80MAC, it was meant as a direct upgrade to the WDG-4 aka GT46MAC (an SD70MAC derivative). The locomotive series is named Bheem, after the strong Pandav brother from epic Mahabharata. The loco has the two-stroke Turbocharged EMD 20N-710G3B-EC (20 cylinder engine) of the EMD SD80MAC and an AC-AC transmission. Since the loco has been developed by installing a v20-710 prime mover and replacing the standard v16 in the WDG4 GT46MAC locomotive, the model was re-designated by adding 4 to the predecessor model, with GT-46 becoming GT-50, owing to the number of cylinders going from 16 to 20, thereby making it the First EMD locomotive in the GT-series to use a v20-710 engine.
The class was stopped only with seven units due to poor tractive effort – it provided only 560 kilonewtons, which is just 20 kilonewtons more than the WDG-4. Also, the v20-710 powerpack having high fuel consumption, similar to why the original SD80MAC were discontinued and were ultimately scrapped. Compounding the issue was Indian Railways aiming for complete network electrification as part of the Net Zero-Carbon Emission programme, during which it discontinued building EMD 710 locomotives and transitioned to greener diesel locomotives based on General Electric (GE)'s GEvoEvolution Series platform. Examples of such are the 4,500 hp (3.4 MW) WDG-4G (GE ES43ACmi) that uses the 12-cylinder version of the GEvo Prime Mover, and the 6,000 hp (4.5 MW) WDG-6G (GE ES57ACi) that uses the 16-cylinder version of the same engine.
