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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 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 Turbine Engine–like sounding property 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. They are numbered from #12001 upward.
As of August 2007, 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, 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 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.
A three WDG-4s standing at Castle Rock.
