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Originally Posted by kalee20
Thanks for informative post and supporting literature Steve! So basically with the series-wound DC motors, auxiliary coils were completely necessary for regenerative braking. Makes sense!
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No problem, but I suspect that in what I said I sacrificed precision for concision. In the railway case, separate excitation of series-wound motors for electric braking purposes was achieved by using the existing series field for this purpose, power-brake changeover switches (somewhat like reverser switches) being used to separate the field circuits from the armature circuits. Additional field coils were rare in railway DC traction motors.
More generally, re the use of existent DC three-wire distribution systems for AC, I imagine that this could explain the origins of the standard American three-wire system of single-phase AC distribution. I suppose that one probably inadvertent benefit of the three-wire system would be that, assuming a statistical distribution of appliances on each side, there would be much reduced net DC on the transformers secondaries from the use of AC-DC radio and TV receivers.
Cheers,