AC4400 CW.
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Builder :
General Electric
Electricity :
AC
Length :
73' 2"
Width :
10' 3"
Height :
15' 5"
Weight :
210 tons
Cylinders :
16
Wheel Diam :
42"
Fuel Tank :
5000 gal
Max Speed :
74 mph
Horsepower :
4400
     

This is the "AC" version of GE's popular dash 9 series of locomotives. The inherent characteristics of three-phase AC motors make them virtually free from the overheating that plagues DC motors operating at maximum load. Where DC-traction locomotives are limited by short-time motor ratings when operating at maximum load, AC locomotives can operate a maximum load at virtually any speed with minimal risk of motor damage or stalling. In addition, three-phase AC motors offer greatly improved wheel-slip control and extended range dynamic braking, both of which aid in operating heavy trains in graded territory while reducing costs due to the requirement for addtional locomotives. For example DC-traction locomotives can only can only use dynamic brakes to slow a train down to about 10 mph without risking motor damge. However, with AC traction, dynamic braking can be used to virually a complete stop. This improves train handling and greatly reduces brake wear.

In addition, advanced motor and wheel-slip control has allowed for much higher adhesion rates. Traditionally, tractive effort was calculated on DC locomotives using a 25% factor of adhesion. Through the control of wheel slip, GEs AC diesels have dry-rail adhesion factors close to 40%. This translates to much higher tractive effort ratings for AC locomotives than was possible with DC locomotives of the same weight, which gives AC locomotives much greater pulling power at slow speeds.

By the 1990s advances with this technology conviced American Railroads to commit to adapting it for heavy service (Powder River Basin coal haulage). However, the capital cost of an AC traction locomotive is consider higher than that of the more conventional DC traction motor model. The AC version of these locomotives are characterised by the larger cabinet located behind the cab on the left hand side of the locomotive.