Western Railroad Discussion > Question about locomotive motor transitioning

I read in an operators for a GP9 that the DC motors employ automatic transitioning. This means that the control electronics switch the motor's field and rotor windings between a parallel connection of two traction motors in series, and a parallel connection of all four traction motors. Also, the field windings of the motors could be shunted to reduce the back emf of each motor. There are four motor configurations used depending on the speed of the locomotive, series-parallel (slowest), series-parallel shunt, parallel, and parallel shunt (fastest). The GP9 documentaion suggests that automatic transitioning was a relatively new innovation. My question is what locomotives required manual transitioning of the motor configuration?

Chad

Pretty well anything older required manual transitioning. In some cases, it could be automatic upward, as speed increased, but require manual downward transition. Examples of manual transition locomotives include the F3, and switchers like the SW-1200.

Are there still locomotives in active use without automatic transitioning?

Chad

When transistion occurred on those older locomotives, it sounded just like an automatic transmission shifting as the engine speed dropped.

Paul Ramer
Cincinnati, OH

Strictly speaking the new stuff runs without transition in that the motors are connected in
permanent parallel

rehunn Wrote:
-------------------------------------------------------
> Strictly speaking the new stuff runs without
> transition in that the motors are connected in
> permanent parallel

EMD went to "permanent parallel" traction motors with the 50-Series locomotives (using, instead, "generator transition" in which the alternator main windings are reconnected as speed increases or decreases).

The new Railpower hybrid, Railpower genset and National Railway genset switchers are even more different ... their four DC traction motors are independently-controlled (like the AC traction motors under a GE AC 6-motor unit). With "conventional" 4-motor permanent-parallel-connected-motor units (like a GP50 or GP60), when one motor slips, the alternator output was reduced to control the slippage of the weakest motor. With the GE ACs (and the hybrids and genset switchers) ... when one wheelset slips, the other wheelsets can take up the load.

All EMD switchers have automatic transition except for very early pre-1950 units such as the NW-2/NW-3/NW-5/early SW1's. Most units had a transition forstalling switch on the control stand to keep them in series for switching or allow automatic transition for road service. Many had to close the throttle when in series-parallel to get them back into series after they had made transition. Late models such as the SW-900/SW-1200 had a three position selector; switching which bypassed the load regulator for quick starts such as kicking cars; series which loaded the generator through the load regulator and automatic; which allowed transition into series-parallel once the voltage/current parameters had been met.

The NW-5 had a manual transition switch similar to a reverser except that it was shifted with a lever inserted into a hole in the moveable portion. It was either a series machine or for road service a series-parallel for road service. The GN 187 has this still intact.

Were older locomotives built with manual transition given automatic transition during rebuilds? Would seem to be a logical, smart change to make.

The pre-Century Series ALCOs on the Spokane, Portland & Seattle were all manual-only transition. After the BN merger it was not unusual to find power consists where we had to rearrange the order of the units to get a leader which was capable of controlling manual-only trailing units. Pictured is the ammeter and speedometer on the SP&S 856 which I ran for years along with a snip taken from the FA operating manual showing the shifting speeds for our 65 MPH-geared locomotives. It was interesting that the manual specified that the transition lever could be moved to any motoring position when in any throttle position. While that may have been allowed by ALCO, the reality was that you needed to make a quick reduction of the throttle to at least the sixth notch when shifting from third to second unless you wanted a tremendous fireworks display and a resounding boom from the power contactors in the electrical cabinet. When making the move on an ascending grade it was a very quick two-handed operation in order to lose as little speed as possible.

---

> All EMD switchers have automatic transition except...

If they have transition at all, you mean. Many (?) don't.

> EMD went to "permanent parallel" traction motors
> with the 50-Series locomotives ...

GP40-2s were permanent parallel-- and most (all?) GP40s too.

It used to be they started in "Series", went to "Series Parallel" and then "Series Parallel Shunt".

When ATK took over they wound up with a bunch of the UP passenger units. What we didn't know, was they were manual transition. Burned a lot of them up before ATK found out and put a bulletin to all the railroads.

Nudge