A reply that is anything but quick: The mention of Train Shed Cyclopedia and a search on the internet has resulted in me buying two Cyc issues, 15 and 66. Interesting info about heavy US electrics. Judging by a GN W-1 operator's manual (also on the 'net) the selection of series or paralell was made manually while standing still, thus no transition, automatic or othewise. Thank you for the replies to my initial question!
Train Shed Cyc #66 reproduces the RME article on the W-1. It says six traction motors were connected in parallel, the two sextets being in series, and it doesn't mention any reconnection.
But the four traction generators were in parallel for freight and series-parallel for passenger; presumably that "transition" was manual.
The generators on the motor generator sets were very similar in operation to the traction generators on diesel-electric locomotives. The main difference were the M-G generators were set up for regenrative braking (i.e. they became the motors and the big 25 Hz motor then became the generator).
It would be expensive to build a generator that could handle the current draw for low speed high tractive effort running and also provide sufficient voltage for high speed operations - note this applies to both M-G equipped electrics and diesel-electrics. The most common work around was to operate the motors in series at low speeds as two motors in series will have half the current draw from the generator as the same two motors in parallel. The downside is that series connection requires a higher generator voltage, but that's not a problem at low speeds. At higher speeds, the motors will be switched to parallel connections, to keep the generator voltage within limits. Since each motor will be drawing less current at high speeds, the sum of the motors' current draw will remain within rated limits of the generator.
For more information, search for transition control for diesel-electric locomotives.
- Erik
The October picture of a Great Northern calendar featured both W-1 electric locomotives coupled together. Those locomotives had 12 traction motors that were fed from two motor-generator sets. An internet web site has published the operator's manual for these remarkable locos. There seems to have been a selector handle for either Series or Parallel operation, suitable for freight or passenger service, I imagine. How were the traction motors connected in series and parallel, respectively?
While I am on the subject, is there a technical description, a drawing or even a circuit diagram to be had anywhere, on the W-1?
Our community is FREE to join. To participate you must either login or register for an account.