Diesel Engine. Three different engine diagrams can be found in U25 manuals. These are GE diagram numbers E9900, E9900A and E9900B. These show numerous yet small detail changes, but it is known that in 1962 the firing order of the engine was changed. In one manual for the U25, diagram number E-13461 is included. This is the "steel cylinder head, single exhaust pipe" engine which appears to have been in development not only for the U28 but actually also for the U30. In one sense, then, it could be considered that operational experience with this new design for the U30 was being rolled up by every U28 built. It is known from GE material that the engine pictured in E-13461 is also known as the FDL-16D. It is likely that GE considered the earlier versions as A, B and C in correspondence to the E-series drawing numbers given earlier.
Continuous speed and power matching. GE officials and design engineers stated publicly numerous times that they wished that railroads would only operate high horsepower per axle units with other high horsepower per axle units, which would make power matching unnecessary. They also knew that railroads could not promise to do this, and stated that power matching had to be included to protect the traction motors of the new GE locomotives.
The U25 and U28 used a system which measured voltage drop in the traction motor shunt field windings, and inferred temperature from this. If the limit were exceeded, protective action occurred, and the Automatic Power Matching system went into action. It caused the ORS solenoid on the governor to be briefly energized about 15 times per minute. The resulting lowered average position of the load regulator caused excitation to, on average, be lowered. This went on for seven minutes. If the condition had cleared by then, normal operation resumed. If not, the seven minute timer restarted, and protection continued.
This was not the case with the U30 units. In these units, no detection took place, and no timer existed. When fitted with Automatic Power Matching, this system was always in operation. One GE representative was asked during a meeting of the Railway Fuel and Operating Officers' Association how this system would appear to a locomotive engineer. The response was that if a train were beginning to ascend a grade at speed, as that speed dropped down to around 20 MPH or so, the engineer would notice load current rise, but then hold steady at the continuous limit of 1195 amps. The train speed would then balance out at some speed below 20 MPH as lower powered units began to take their share of the load at a lower speed. However, from starting up to about 8 MPH the full range of excitation current limit was available to the engineer for starting and acceleration. This new system was also mated with an entirely new transistorized excitation and control system, mounted on new modularized printed circuit cards. Special solid state and/or modularized circuits accomplished the functions of matching alternator output to engine output by sensing current and voltage, and by forcing a power curve to the output of the alternator. The Automatic Power Matching circuit was separate from these three other excitation circuits (again, voltage limit, current limit and function generator) and was optional on all U-series units, even the six-axle types. Literally all of the excitation and control system of the U30 was new. Only the old control stand remained, which itself would be replaced by a new "two lever" control stand, still with a 16 notch throttle, in early 1968. |
