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How to hand-test a BLDC motor

Sometimes if you’re buying used, or troubleshooting, and need a quick way to see if anything might be wrong, you can test a BLDC motor with only your hands. It’s not the most accurate test in the world, but catches most problems.

  1. Ensure motor phase wires are not connected to an ESC or anything else.
  2. Verify the motor spins without grinding or rubbing. Put a tad of sideways stress on the shaft and push it and pull it (while turning) to verify it feels smooth.
  3. connect phase A to phase B and verify by hand-spinning that there are moderate choppy brakes
  4. connect phase A to phase C and verify by hand-spinning that there are moderate choppy brakes
  5. connect phase B to phase C and verify by hand-spinning that there are moderate choppy brakes
  6. connect phase A to phase B to phase C and verify by hand-spinning that there are strong smooth brakes
  7. the first 3 should all feel exactly the same strength (important)
  8. verify with A, B, and C disconnected that there are no brakes

This quick hand test can weed out most major motor problems quickly.

If you’re having a problem you’re trying to diagnose, this test can also quickly tell you if the problem you’re having might be in the ESC or wheel drive assembly instead of inside the motor.


For further testing, check this article

43 Likes

Awesome, @b264 thank you for putting this up. The magic of this test must somehow be related to the magic of “It dosen’t matter how you plug in the phase wires, except if it goes backward, switch any two connections”

I can’t wrap my peanut brain around why it works ,but it does.

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Great write up… #article-requests @BillGordon?

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I’ve tried to entice Brian before with promises of money and fame. I’ll be happy to work with him on any write-ups he’s interested in putting together.

3 Likes

Wow, six and a half months with 40 likes and no replies, I thought this was the biggest mic drop of all time but wasn’t going to say anything lest I prod comments. But now that it’s been broken I can speak :rofl:

3 Likes

Be proud and be loud.

2 Likes