Circulating currents in ~100 words.

What are circulating currents, why are random-wound windings called random, why should you care? Find out here, with convenient bullet points!

  • In a stranded winding, the total current gets unevenly divided between parallel strands.

    Illustration of the phenomenon.
  • This increases losses. A lot, more often than not.
  • The losses vary randomly motor-to-motor. This is because the strands shift their relative positions between slots, randomly.
  • Regarding this switching, the following seem to hold true:
    1. The positions in one slot depend on the position in the previous slot.
    2. Strands move in bundles: those close to each other in one slot, are probably close to each other in the next one too.
  • Ignoring either assumption leads to an unrealistically narrow distribution of total losses.

For further reference, here’s my poster from the PEMD conference this (2018) Spring.

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Circulating currents – Post-it version

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