' ▁Elect ro - M ot ive ▁Division ▁between ▁August ▁ 1 9 7 5 ▁and ▁August ▁ 1 9 8 4 . ▁A ▁variant ▁of ▁the ▁E MD ▁MP 1 5 DC ▁with ▁an ▁AC ▁transmission , ▁ 2 4 6 ▁examples ▁were ▁built , ▁including ▁ 2 5 ▁for ▁export ▁to ▁Mexico , ▁and ▁four ▁built ▁in ▁Canada . ▁ ▁Development ▁ ▁The ▁MP 1 5 DC ’ s ▁standard ▁Bl om berg ▁B ▁tr uck s ▁were ▁capable ▁of ▁transition ▁and ▁road ▁spe eds ▁up ▁to ▁, ▁allowing ▁use ▁on ▁road ▁fre ights . ▁So on ▁there ▁was ▁a ▁demand ▁for ▁a ▁model ▁with ▁an ▁advanced ▁AC ▁drive ▁system . ▁The ▁MP 1 5 AC ▁replaced ▁the ▁MP 1 5 DC ’ s ▁DC ▁generator ▁with ▁an ▁altern ator ▁producing ▁AC ▁power ▁which ▁is ▁converted ▁to ▁DC ▁for ▁the ▁tra ction ▁mot ors ▁with ▁a ▁sil icon ▁rect ifier . ▁The ▁MP 1 5 AC ▁is ▁ ▁longer ▁than ▁an ▁MP 1 5 DC , ▁the ▁extra ▁space ▁being ▁needed ▁for ▁the ▁rect ifier ▁equipment . ▁The ▁altern ator - rect ifier ▁combination ▁is ▁more ▁reliable ▁than ▁a ▁generator , ▁and ▁this ▁equipment ▁became ▁the ▁standard ▁for ▁new ▁dies el - elect ric ▁locomot ive ▁designs . ▁ ▁The ▁MP 1 5 AC ▁is ▁easily ▁distinguished ▁from ▁the ▁DC ▁models . ▁Instead ▁of ▁the ▁front - mount ed ▁radi ator ▁int ake ▁and ▁bel t - dri ven ▁fan ▁used ▁on ▁all ▁previous ▁E MD ▁switch ers , ▁these ▁have