The 2208 90KV BLDC has a phase resistance of 16.4Ω

I used a Fluke multimeter to measure the phase resistance of the 2208 Gimbal motor listed on the Supported BLDC Motors page. Measured 16.4 ohms. The exact motor I got from amazon is Fityle 2208 90KV 3mm Shaft Gimbal Brushless Motor for 100-200g Gopro3 RC Quadcopter

Just thought I’d mention it so the supported BLDC motors page could get updated with that phase resistance.

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Thanks @jakabo27.

Question to you and forum in general. Most bldcs are star formation, some are delta.

If you have a star and measure 16ohms, should you divide by two as you are effectively measuring two phases?

Strictly speaking, yes. Given the following picture, if you measure resistance from A to B you are measuring phase to phase resistance. If you measure from A to N (which is exposed in some motors) you are measuring phase resistance.

image

Oh interesting, good point then. I just measured between pairs of leads, so yeah I measured phase to phase resistance. However, I’m using the SimpleFOC Shield V2.03 and it didn’t overheat or anything with this motor despite being under 10 ohms per phase with that new math.

Sorry to add to the confusion, but the 2208 90KV is advertised to have a resistance of 13.3Ω here and here.

I have two such motors. Measured resistance - 12.5Ω.

The BLDCs I’ve removed from old HDDs mostly had 4 pins - they are wye (star) wound with the center point is brought out. When measuring those you can see nicely that one of the pins has half the resistance when measured against the others. That’s the middle pin.

I guess for motor calculations you may need the phase resistance.

But for the purposes of calculating your voltage limit to prevent things burning, phase to phase resistance is fine.

I’ve bought quite a few motors by now for playing with SimpleFOC and figuring out which is best suited. I can say that for motors in that price range, I would neither trust the listings to be correct, nor would I expect a lot of consistency from the motors themselves. Sometimes I’ve found 1Ω or more difference when measuring the different phase-to-phase resistances - of the same motor!

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