I have a quick question, how do I know how many phases a BLDC has? For example, an E-bike motor kit has three motor wires: yellow, green and blue. It also has three wires for the hall effect sensors: yellow, green and blue plus two more wires for powering up the sensors: black and red. By intuition, I believe it is a three phase BLDC because it has three signals for motor control plus three signals for feedback. Is that correct?



1 Answer 1


Nearly all BLDC motors have three phases. Like, more than 99%, as far as I know. But if it's oddball and has two, then it needs three wires (phase 1, phase 2, and common) or four. Similarly, an oddball 3-phase BLDC may have six wires (i.e., the manufacturer decided to bring out each phase individually).

The only way to tell for sure is to do some continuity checks, then put it up on an oscilloscope, spin it, and look at what it generates.

  • \$\begingroup\$ You mean to put in an oscilloscope the three motor wires? or the three hall effect sensors? \$\endgroup\$
    – Moctezuma
    Sep 26, 2019 at 0:46
  • \$\begingroup\$ The motor wires. \$\endgroup\$
    – TimWescott
    Sep 26, 2019 at 0:47
  • \$\begingroup\$ Don't bother testing it, 3 motor wires = 3 phases. \$\endgroup\$ Sep 26, 2019 at 2:46

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