The Indian locomotive class WDG-4 (EMD GT46MAC) is a type of six-axle (Co-Co) freight-hauling diesel–electric locomotive with AC electric transmission designed by General Motors Electro-Motive Diesel[1] in 1997–1998 for Indian Railways, where they are classed as WDG-4. Derived from the EMD SD70MAC, it is powered by a 4,000 hp (3,000 kW) 16-cylinderEMD 710G3B prime mover. Thirteen were built by EMD as order #958647, and a further eight were exported in kit form and assembled in India. The class entered service in 1999. A Dedicated Passenger version of this locomotive, the WDP-4 (EMD GT46PAC), has also been produced, with a Bo1-1Bo Wheel Configuration, which entered service in 2001. These locomotives are also famous for, and can be identified by, the distinct jet-airplane–like sound of the EMD 710 prime mover.
Further construction has been under license in India by the Banaras Locomotive Works (BLW), with the first purely indigenously built WDG-4 locomotive, numbered 12022, that rolled out in 2002. More than 60 additional locomotives have been built as of 2006[update]. They are numbered from #12001 upward.
As of August 2007[update], EMD and DLW have begun building GT46ACe's using IGBT technology to replace the older gate turn-off thyristor technology and along with increase of 500 hp, ie, 4,500 hp (3.4 MW), using the Newly tweaked EMD 16N-710G3B-EC, like the passenger WDP-4B have been produced. Newer versions with widened Piggy-face cab profile for enhanced visibility, just like the later variants of WDP-4's and WDP-4B's were also produced.
As of February 2013[update], DLW began building the Dual Cab version, EMD JT46ACe, called WDG-4D, based on the passenger variant WDP-4D locos, same for both-side visibility. Here again, many features, including IGBT and 4,500 hp have been carried on from the single cab GT46ACe's. The first WDG-4D, numbered 12681, is named "Vijay". Later WDG-4D's were numbered from 70301, as the 12*** series came to an end in 2014 and got switched to 70*** series. Over 1,500 such locomotives, including both WDG-4's and WDG-4D's are currently in operation.
Indian Railways has also developed the WDG-4 series into EMD GT50AC (aka WDG-5), using a v20-710G prime mover, based on the SD80MAC, rated at 5,500 HP (4,130 kW). However, this locomotive has turned out to be a Failure, due to various reasons.
Since the year 2017, BLW (DLW then) began manufacturing such locomotives for Non-Railway Customers. The first such locomotive, which would be a Dual-Cab WDG-4D, rolled out to serve Odisha Power Generation Corporation (OPGC), in March 2017. Three WDG-4D locomotives currently serve OPGC.[as of?] As of 2024, two new Single-Cab Piggy-face WDG-4 locomotives have been manufactured and rolled out for Obra Thermal Power Station, based at Sonbhadra, Uttar Pradesh.
