I am trying to convert a wind generator to a brushless motor.

enter image description here

As you can see at the image, it has 16 magnets and 12 coils. The coils are connected as 3 phase, star connection, so I have 3 output wires to play with. The fourth which is the common connection is buried in epoxy and its unreachable.

I already tryed a BLDC Three-Phase Sensorless Brushless Motor Speed Controller, but it doesn't run smoothly, it makes a vibrating noise, like its not synchronized and it feels like it brakes its self. So the speed is ridiculously slow (like 60 rpm at 12v).

Is there any circuit to run it properly as a brushless motor? Thanks!

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    \$\begingroup\$ The issue would be the algorithm, not the circuitry \$\endgroup\$ Commented Dec 29, 2019 at 12:00
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    \$\begingroup\$ If used as a generator, when spun at a precise and known rpm, what do the output waveforms look like. \$\endgroup\$
    – Andy aka
    Commented Dec 29, 2019 at 12:14
  • \$\begingroup\$ Good suggestion Andy.. Then load generator with maximum power and record waveforms and then implement FOC commutation. \$\endgroup\$ Commented Dec 29, 2019 at 16:18
  • \$\begingroup\$ Are you sure this is a generator and not a stepper motor? It this a factory-made or home made machine? \$\endgroup\$
    – user80875
    Commented Dec 29, 2019 at 17:06
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    \$\begingroup\$ "So the speed is ridiculously slow (like 60 rpm at 12v)" - what voltage does it produce at 60rpm when operated as a generator? You picture looks a bit peculiar. Can you show us a photo of the actual machine? \$\endgroup\$ Commented Dec 29, 2019 at 22:49

1 Answer 1


It should be possible to use 3 hall cell magnetic field detectors to provide commutation sensing. There are numerous IC's that accept 3 hall inputs and provide motor drive signals.
Which is most appropriate depends on the alternator / motor ratings.
eg the controllers in "hover boards" usually use 3 hall sensors and will drive motors in the hundreds of watts range at voltages typically around 40V - but this could be altered.

What power / voltage / current / RPM do you expect to be dealing with?

Do you have a brand, part number, photo or related web link?


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