I always wondered what this sound was about. https://youtu.be/TM0bOpwxxO8 Sounds... | Hacker News

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		yread on Sept 17, 2017 \| parent \| context \| favorite \| on: As Electric Motors Impove, More Things Are Being E... I always wondered what this sound was about. https://youtu.be/TM0bOpwxxO8 Sounds like there is a steam engine inside (but the 451s are electrical)

2sk21 on Sept 17, 2017 [–]

Those are relay contacts selecting which field windings are getting power. As the locomotive accelerates, the number of enegerqzed coils is reduced in order to reduce back EMF (electro motive force)

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