I forgot to mention, my noise is negligible at very low speeds but also at very high speeds. Above 70 amps, it quiets down a lot. I am thinking this has to do with the shortened dwell time per pole in relation to the pulse width, and that the midrange noise would quiet down with a sine wave input. I am going to try to borrow a sinewave controller from someone when I get back from my next job, and rig some way for measuring noise level, and compare the two. I might also try a gearbox with a higher reduction ratio, to get motor RPM up into that silent zone. Could be the load on the motor contributes to the noise. I know my shaft is not as true as I would like it to be, though it is pretty close. It is a bronze shaft and I am considering going stainless on my next haulout. So far, I have resisted installing any U-joints in my shafting, because my motor mount is very finely adjustable, and I just don't trust them enough to put them in without a demonstrable need.
In my limited experience and possibly flawed perception, BLDC motor noise has a strong "click" component, as the rotor gets micro-flexed to coin a phrase, with each pole passage. Since accelleration is not an issue, it seems that more rotor mass and rigidity might make for a quieter motor without significant performance degradation.
Has anyone done any noise comparisons between axial flux and radial flux motors?
Well I have to fly to Cyprus and catch a ship tomorrow so I may not be on this board as much as I would like, for the next few months. If I don't chime in it's because I am at sea with no or little internet access.
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