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AC vs. DC traction
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Good thread. Couple of thoughts… <br /> <br />I broke some old time hoggers in on AC while I was an EMD field engineer; it was not easy convincing them that they would not burn up the motors. In one case, a road foreman had to run. <br /> <br />Depending on the hill, you sometimes needed th. 4, 5, or 6 to hold a heavy train. If you goof, the train slides back and the brakes apply. After waiting for another try, we had to notch out to 6 before releasing the brakes. THAT was really hard for them to grasp (at first). Imagine being at almost full throttle before leasing the brakes! <br /> <br />Its all about tractive effort, AC does more but comes with a $500k-$700k premium. [DC’s were around $1.5M and AC $2 to $2.2M]. Just look at two 5,000 HP SD80MAC’s replacing four C30’s for Conrail on the B&A, or three SD70MAC’s doing the work of five SD40-2’s for BN. It pays for itself but in the right application. HP equals speed, but AC can pull more (low end torque). Put both together and you have 6000 HP AC’s that can do it all. BTW, DC’s could not put 6000 HP to the rails, they would slip. Its simple (well sort of…) physics. The locomotives would need to weigh too much. <br /> <br />AC invertors are like traction control in a car, which is why you have to take AC from a constant speed engine/alternator set, clean it up (DC), and convert it back to AC with a computer fast enough to make the adjustments. It is like a fly-by-wire jet. Only a computer can get that much HP to the rails. <br />
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