05-19-2012, 01:04 PM
The notches are only there to keep the throttle and the governor in sync with the electrical load. There are ports in the governor that control the fuel input needed to maintain the prime mover RPM and the main generator functions with the switch gear to make transition. You do the exact thing when using the throttle on a car only you don't have the notches. Just forget the notches are there in a locomotive. When driving an auto when you need more speed you have to increase the pressure on the accelerator, when a locomotive is in a certain notch it will keep the engine at a steady rpm, similar to cruise control. the governor is what controls the fuel, but when the load becomes too heavy to maintain a speed in that notch you have to open the throttle more, to let the governor know the prime mover needs more fuel. When you run out of notches, as on a grade, the wheels start to slip and/or the engine stalls.
There is also transition made on locomotives which, to explain, is like shifting gears in a car, but this is done with the electrical switch gear. The Old Alco started in Series, at 6 MPH it made the switch to series parallel, and at 28 would go to parallel shunt. This was done by changing the electrical connections to the traction motors..Maybe EPAW can explain it fully
( I could run the passenger train at ten miles an hour in notch 3, but if I forced transition to parallel I could drop the throttle back to notch one and maintain the speed)
Charlie
There is also transition made on locomotives which, to explain, is like shifting gears in a car, but this is done with the electrical switch gear. The Old Alco started in Series, at 6 MPH it made the switch to series parallel, and at 28 would go to parallel shunt. This was done by changing the electrical connections to the traction motors..Maybe EPAW can explain it fully
( I could run the passenger train at ten miles an hour in notch 3, but if I forced transition to parallel I could drop the throttle back to notch one and maintain the speed)
Charlie