Because of the weight of a single 11,000 volt traction-power transformer, the EP-1 was equipped with two which were “auto-transformers” , an auto-transformer a single- winding design. Refer ( via hathitrust ) to the Street Railway Journal ,Volume 30 , Aug. 1907 , pags 278-285 , for an illustration of the transformer-motor connections thru “unit-switch” contacts with “blow-out” coils.You don’t “start” a locomotive as you do an engine; you advance it from zero speed to full-speed.
Sounds like you’re proposing a remake of the Westinghouse “Quills” with 1250V motors instead of the 750V motors used. One issue with running a bunch of motors in series is insulating the motor windings for 5kV and figuring out how to prevent arcing between the brusholders and motor frame.
OTOH, some of the Thury system implementations were running 75kV or more with lots of motor’s in series, albeit the motors were on insulated mounts and had insulated shaft couplings.
The bipolar motors were lacking interpoles, so it would have been a challenge to go higher than the 1000V on the Milw Bipolar’s. Note that traction motor voltage pretty much topped out at 600VDC prior to interpoles. IIRC, the motors for the M-G sets were 2 pole design to allow enough commutator bars between brushes, but had interpoles to improve commutation.
Note that the 5kV proposal made sense with the existing traffic and number of locomotives. An increase in traffic would have lead to a higher cost for the 5kV locomotives than with the 3kV locomotives.
Actually this is the definition for any voltage-controlled electric motor, and technically includes bringing up a rotary converter. It can be confusing to those only familiar with internal combustion to read about ‘starting resistances’ too.
I was fortunate to have people explain to me both on IRT subway equipment and on PRR MP54s how to get smooth physical car starts from rest and then controlled acceleration with restricted tap control. It’s something of an art.
Incidentally there is more required when opening HV contactors than when initially closing them: when you look at the action of blowout coils, arc chutes, etc. you will gain a greater appreciation for the practical joys of switching heavy inductive loads…
Add BC Rails GF6C to the single cab club. Yes the 1st gen E60C were single cab. The E60C-2 was the only modern domestic freight double cab electric built. Seven are still in operation on the Desert-Western located in the Uinta Basin.
Very interesting video, another example of a moving picture being worth thousands of words.
Note that this is still comparably low-voltage; if division as shown is into ‘30-volt arcs’ this is no more than about 277V. Presumably there is a version for up to ~480V, but you’re starting to get into the range even there where a combination of (induced by arc current) magnetic field and air blast is desirable to clear the conductive plasma from between the opening contacts. How the energy is dissipated from the extended plasma is another matter, one of more than trivial concern in ‘arc flash’ safety.