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BNSF #9939 (EMD SD70MAC) | by cliff1066™
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BNSF #9939 (EMD SD70MAC)

The SD70MAC (colloquially known as a "Mac" or a "Mac 70") is very similar to the SD70M and SD70I (the SD70I's WhisperCab feature was a build-to-order option), the main difference being that the SD70MAC uses AC traction motors. AC motors, while more simple and reliable than DC motors, require substantially more expensive inverters to generate a variable-frequency AC signal. The majority of SD70MAC models were produced with 4,000 horsepower (2,980 kW) EMD Model 710 prime movers, while later-production SD70MACs are rated at 4,300 horsepower (3,210 kW) and feature SD45-style flared radiators. They were also offered with a head-end power generation system for passenger trains. (The SD70MAC is no longer produced due to EPA regulations and has been replaced by the SD70ACe.) Over 1,500 examples of this locomotive model were produced. Purchasers include Burlington Northern (now BNSF), Conrail (engines now owned by CSX), CSX, TFM/Kansas City Southern and the Alaska Railroad. (Wikipedia)

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Taken on October 11, 2007