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When BLDC motor is used as generator, how does the amount of poles effect the frequency of the 3 phase AC that it generates? For example, if I had a motor with 8 poles and I spun it at 50 rpm, what frequency 3 phase AC would it generate?

Maple
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KitKatKittens Yes
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    "the frequency it outputs": a motor doesn't output frequency. What do you refer to? Do you mean a brushless DC motor used as a generator? That generally doesn't work, because a brushless DC motor is typically a three-or-more phase AC motor with current source electronics to convert the DC to AC; and that doesn't work the other way around.- – Marcus Müller Aug 06 '18 at 17:56
  • @MarcusMüller https://electronics.stackexchange.com/questions/322321/can-any-dc-brushless-motor-be-used-as-a-generator – Maple Aug 16 '18 at 15:16

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For an 8-pole motor there are 4 complete cycles of each phase per rotation, so rotating it at 50 RPM gives you 200 cycles per minute or 200/60 Hz.

BTW, an "8-pole" 3-phase motor has 24 magnetic poles.

Spehro Pefhany
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  • I'm not sure what you mean by 24 magnetic poles. Could You explain? – John Birckhead Aug 15 '18 at 19:51
  • @JohnBirckhead Poles are in pairs, so the stated number is always even. They are per phase so multiply by three. [This](https://electronics.stackexchange.com/questions/224797/3-phase-induction-motors-with-poles-not-equal-to-3x) answer covers it. – Spehro Pefhany Aug 15 '18 at 20:05
  • The link shows only motors whose number of slots are equal to the number of poles times the number of phases. I am a little concerned that readers might think that this was always true and become confused. – John Birckhead Aug 15 '18 at 21:40