Dunno about theGEC-Cs, but the later EMDs used alternator transition instead of traction motor transition.
There could be some benefit from using AC motor transition, connecting two windings in series at low speeds and in parallel at high speeds. This would ease component requirements for the inverters.
The change from using traction motor groupings was required by EMD’s adoption of Super Series wheel slip control. It always amused me that “Super Series” required that all motors be in parallel, but that arrangement allowed single motors to be isolated when they slipped, rather than cutting power to all motors when an axle slipped. The "Series"name referred to series wound motors. I understand that ASEA was involved in the development and they had a system which was used with separately excited motors.
In the cab of the lead unit with conventional wheelslip control with 37 000 long tons on the drawbar, you could tell when the power cut on a trailing unit long before the remote wheelslip bell rang. I never rode on such a train after they started using SD50s but I’m sure they worked better than the old Alcos.
I recall reading in material from the time of the introduction of Super Series that GE had been using internal switching in alternators before EMD introduced the AR11 to replace the AR16. One of the reasons quoted for the change was greater fuel economy, but I don’t understand why changing an alternator would save fuel, at least, not on its own…
I was disappointed that nobody commented on my earlier post about directly fed 50Hz motors. The demonstration model in the video suggested that the motors were larger in diameter than the driving wheels, and were located well up in the bogie structure. I wonder if larger diameter commutators would reduce the chance of flashover with a high frequency AC current.
Peter
MS: I didn’t comment because such large 50Hz commutator motors are entirely new foir me. At the MIT EE Department, 1949 - 1957, EMD Summer 1952, they were considered impracticaql, except in small applications, such as Lionel and Gilbert American Flyer. This is now old technology, but new for me.
50 Hz single-phase traction motors were certainly larger than their low-frequency counterparts, which in turn were larger than the DC types. As compared with low-frequency motors, the required lower flux density (to manage the transformer EMF problem) meant more poles and so larger commutators, etc.
Here are some comparative numbers from a 1977 SBB (Switzerland) paper, for nominally 1200 kW motors:
DC Motor:
8 poles
Armature diameter 760 mm
Weight 3640 kg
Single-Phase 16⅔ Hz motor:
10 poles
Armature diameter 820 mm
Weight 3860 kg
Single-Phase 50 Hz motor:
20 poles
Armature diameter 990 mm
Weight 4600 kg
Power 1050 kW
Note that even with its larger armature diameter,
It’s always nice to get good information from actual experts in a technology. We’re fortunate to have them actively posting here.
I suspect this had to do with better control of the field so that the Woodward governor could be commanded to make better power at a lower nominal notch.
You’d have to use ‘monomoteur’ or body-mounted motors – and these are certainly a ‘thing’ – but you’d need additional room in the carbody for the motors and associated support. American practice has generally used some variant of wheelbarrow suspension with the smaller wheel sizes.
The SD70m still make transition. Ours around 25 and 40 mph. I’ve noticed foriegn power sometimes have a different setting, a few mph difference.
That way going up a stiff grade with them down on their knees you get to feel the lunge, has they momentarily drop the load and then start pulling again, twice. All the time hoping it doesn’t break a knuckle or yank out a drawbar.
Jeff
Pneudyne,
Great to see you posting here, always enjoy reading your well researched and informative posts on that other RR forum.
Dave
Hi Dave, thanks very much for the welcome and the kind words. There are some very interesting thread topics active here!
Cheers,
Chopper control was used for DC locomotives. As far as I know, aside from experimental units, the first series-produced type was the SNCB, Belgium 20 class of 1975, for its 3 kV DC system. These were six-motor units (C-C) with sepex motors. Other major 3 kV DC systems who used chopper locmotives included FS, Italy and SAR, South Africa. The interval between the advent of chopper controls and the arrival of inverter/AC motor techniques seems to have been relatively short as technology epochs go.
Cheers,
I would like to add that the newest French TGV powercars do use permanent magnet AC traaction motors.
Interesting video!
The four locomotive types, BB12000, BB13000, CC14000 and CC14100, including their traction motors and traction motor mountings were fully described in a French language book:
Pascal Dumont
Les Locomotives Electriques Monophases de l’Artere Nord-Est
Les Editions du Cabri; 1994
ISBN 2-908816-15-6
This has more technical content than is usual for railfan books.
Brief descriptions of the CC14000 and CC14100 types were provided in this book:
A.T. Dover
Electric Traction
Fourth Ed
It may also be noted that single-phase traction motors were necessarily relatively low voltage machines, this to keep the transformer EMF and its deleterious effects (commutator sparking) within bounds at starting and lower speeds. The restriction on voltage was greater with increasing frequency.
16⅔ Hz motors typically had rated voltages of 400 volts or so.
25 Hz motors of conventional construction were often around 230 volts, give or take. With the use of resistance leads, that increased to around 330 volts.
50 Hz motors were a more difficult case. If conventional construction were used, then a voltage around 130 volts would be required, which was really too low, as it required exceptionally high currents. In practice it appears that either resistance leads were used, or a duplex lap winding for the armature, each allowing a rated voltage of around 230 volts.
Single-phase motors though could operate on much higher voltages at higher rotational speeds. The higher voltages were easily provided by overvoltage taps on the transformer. This facility accounted for the prodigious short-term ratings of single-phase motors and their associated locomotives. As an example, the numbers for the PRR E2b class were 2500 hp continuous, briefly 5200 hp at 33 mile/h at the end of the accelerating period, and short-term 4240 hp at 41.5 mile/h on r
Here’s the Google PDF of the '209 patent:
https://patentimages.storage.googleapis.com/14/ee/53/ad6b803e3a309e/US2230209.pdf
For those who wish to spend an idle hour with the fascinating things James Blunt developed, go here:
https://scholar.google.com/citations?user=5qNZF1sAAAAJ&hl=en
Here’s the Google PDF of the '209 patent:
https://patentimages.storage.googleapis.com/14/ee/53/ad6b803e3a309e/US2230209.pdf
For those who wish to spend an idle hour with the fascinating things James Blunt developed, go here:
https://scholar.google.com/citations?user=5qNZF1sAAAAJ&hl=en
Note that when you click on the individual items, you have a link directly to the Google API copy of the patent at upper right.
Referring to the original request by Enzoamps, the following may have some utility:
http://www.traction-electrique.ch/documents/SummarET.pdf
It is an online summary of the book “Traction Electrique”. It does provide some basics for the various types of traction motors, and is reasonably recent (2012). The translation from the original Swiss-French is at times idiosyncratic, but not an impediment.
Cheers,
[quote user=“Pneudyne”]
M636C
I found this French Documentary, with an english commentary that deals with early French 50 Hz electrification. Sadly the colour is quite faded but it gives an excellent view of the operation of both steam and electric locomotives.
https://www.youtube.com/watch?v=7l6v2qLYg4Q
Interesting video!
The four locomotive types, BB12000, BB13000, CC14000 and CC14100, including their traction motors and traction motor mountings were fully described in a French language book:
Pascal Dumont
Les Locomotives Electriques Monophases de l’Artere Nord-Est
Les Editions du Cabri; 1994
ISBN 2-908816-15-6
This has more technical content than is usual for railfan books.
Brief descriptions of the CC14000 and CC14100 types were provided in this book:
A.T. Do
I wonder if any of these rotary-converter locomotives are still in operation today. Have any been coverted from rotary-converter to solki-state-converter?
There was a proposal to convert one CC14000 to use static conversion, but this was stillborn. The CC14000 fleet was all out of service by the end of 1981. The CC14100 fleet lasted until the mid/late 1990s.
The CC14000 was viewed as being a somewhat delicate machine, not so much in respect of its equipment per se, but in terms of the proper adjustment thereof. On the other hand, when working properly, it had good performance, with much better regenerative braking than the CC14100, which was otherwise seen as robust.
The CC14000 could be seen as the final development of the phase-converter locomotive using electro-mechanical equipment. Preceding it was the Ganz-Kando locomotive built for the Hungarian Railways as its V55 class . In terms of conversion equipment, this effectively had parallel AC-AC and mechanical power transmission paths. An AC synchronous motor that also served as a single-phase-to-three-phase converter drove a rotary transformer of the pole-changing type, whose output provide five frequency steps from 25 to 125 Hz. Given the stepped nature of the conversion, it had slip-ring induction motors, with the rotor windings connected to a liquid rheostat. Apparently, it did not work all that well, and Hungarian Railways reverted to the motor-generator type, built until c.1962.
In the CC14000, effectively the AC-DC-AC path replaced the mechanical path, so that there were AC-AC and AC-DC-AC paths in parallel.
There was a proposal to convert one CC14000 to use static conversion, but this was stillborn. The CC14000 fleet was all out of service by the end of 1981. The CC14100 fleet lasted until the mid/late 1990s.
-Pneudyne
There was actually a trial carried out in the mid 1970s using CC 14003, coupled to a retired electric parcels van Z4212 which was fitted with an experimental 600kVA inverter, based on a surplus rectifier removed from scrapped experimental locomotive BB 20006 (which started out as BB 8051 on the original 50Hz test section), but which was used as a technology test bed for several years.
(Defrance, page 658)
Of course, a CC 14000 had a continuous rating at one hour of 2640 kW, so it was a limited test, but encouraged future work and cost little, using available equipment.
A similar trial had been carried out in 1971 using another of the original prototype locomotives CC 20002, (originally CC 6052) in which a full set of DC chopper controls was fitted, and used to feed the DC motors of BB 9252. This equipment later appeared in BB 7200 and BB 25200 class locomotives.
(Defrance, pages 30-33)
It appears that the CC 14000 were withdrawn before inverter technology reached a practical stage to allow conversion to the new technology. However, by the time inverters were in use, there were few tasks requiring the slow drag freight tasks performed by the CC 14000 and CC 14100.
Defrance does provide tractive effort/speed curves for CC 14000 and CC 14100 types. While the CC 1410 diagram is typical of DC traction, the CC 14000 provided 50% more tractive effort at maximum speed (only 60km/h ~35 mph). Down at 10km/h, running full current on the dc to 3 phase converter (3000amps) a tractive effort of 50 000 daN was available compared to a continuous rating of 22 000 daN on the CC 14100.
This is of course similar to the ratings seen now with AC traction compared to DC traction, but the CC 14000 could not be relied upon to provide
If nothing else, the CC14000 provided SNCF with some early experience with variable frequency three-phase traction motors, and may well have established them as a desideratum to be implemented as soon as suitable conversion technology became available. SNCF’s early experience with on-board inversion, albeit at fixed frequency and single-phase, would have been with its AC locomotives equipped for regeneration, and using excitron rectifiers.
Relative power distribution through the two conversion pathways for the CC14000 was quite interesting. At full power, the AC pathway, essentially all-electric, stayed at around 2000 kW across the speed range. The DC pathway, involving two mechanical transfers, started at close to negative 2000 kW at zero speed, crossing the zero power line at around 22-23 km/h, and increasing to 3000 kW at full speed.
Traction motor weights given for the CC14000 and CC14100 were the same, at 1950 kg. So the higher power-to-weight ratio advantage of the AC motor advantage was quite apparent.
In my June 22 posting, I quoted some comparative motor sizes and weights from an SBB paper. The latter also included a three-phase motor, whose details I did not then quote, but which were:
Three-Phase Motor (1200 kW)
4 poles
Armature diam