BTW, the Sevcon web site
http://www.sevcon.com/pages/millipak4Q.html
says the milipak switching frequency is 16kHz, I don't know why they think that would be out of human hearing range, we usually see 20kHz cited as the upper limit in normal young humans. Kelly says they operate at 16.6kHz, again a high whine for most people.
Paul
--- In electricboats@yahoogroups.com, "tartan27hull157" <tartan27hull157@...> wrote:
>
> Tom,
>
> Thanks much for the detailed analysis of the different noises your "silent drive" makes.
>
> John, in your Pacemaker, do you find both of the kinds of noises Tom describes? That is, the constant, high-pitched whine (which I believe is the pulse-width modulation) from the controller, and other tones that vary in pitch with the motor rpm?
>
> Does anyone have a Kelly controller whose PWM whine they find audible?
>
> Thanks, Paul
>
>
>
> --- In electricboats@yahoogroups.com, John Raynes <johncraynes@> wrote:
> >
> > Tom,
> >
> > Thank you for bringing up this topic about motor and controller noise in
> > your electric launch. I have an old 26' Pacemaker Powerboat I converted to
> > run on electric propulsion last year. She runs on a brushless DC motor and
> > controller and was somewhat loud as well. Although she runs good she has
> > that same whine. I hope other electric boaters will provide some answers to
> > this post.
> >
> > John Raynes
> >
> >
> > Nov 8, 2010 at 9:07 PM, Tom <boat_works@> wrote:
> >
> > >
> > >
> > > A few notes on noise aboard Grace, our 21' launch:
> > >
> > > I ran my MARS PMAC ME0201013001 motor with the Sevcon MilliPak controller
> > > outside the boat before installation just to get a baseline on the noise I
> > > could expect.
> > >
> > > I wasn't expecting silence, but was hoping for something equivalent to an
> > > AC induction motor, since there would be no brush noise.
> > > Well, I was being too optimistic.
> > >
> > > The controller makes a distinct, unvarying, and piercing whine at all
> > > speeds, even at rest. It is easily heard, but not obnoxious, with the
> > > floorboards down. The manual says it is inaudible in operation. I'll have to
> > > disagree.
> > >
> > > The motor has a distinct cogging effect when rotated slowly by hand, so I
> > > had my suspicions that it wouldn't run as smoothly at low speeds as an AC
> > > induction motor. In fact, there is a loud rumble at very low speeds. This
> > > isn't really a consideration, since the motor is rarely run at such low
> > > speeds.
> > >
> > > At any other speed the motor is reasonably quiet, and very smooth running.
> > >
> > > The controller creates a loud singing noise at various speeds. At other
> > > speeds it is silent (except for the continuous whine)At first I was
> > > convinced that the prop was at fault (15x12 3 blade), but Dennis Wolfe asked
> > > me to look into whether the noise could be coming from the motor, as a
> > > function of the output of the controller, and it certainly is.
> > >
> > > The synchronous belt reduction gear (2.8:1) is very quiet, allows for very
> > > easy and exact alignment with a self-aligning thrust bearing, and might
> > > serve as a weak link in the system in case of hitting a log with the prop
> > > (let's hope we never find out).
> > >
> > > Grace has isolating bushings in the motor mounting plate, but no other
> > > sound reduction, yet.
> > >
> > > I don't mean to sound negative, I really like being electric, but I did
> > > have very high expectations of near silence, which doesn't seem to be
> > > realistic.
> > >
> > > -Tom
> > >
> > >
> > >
> >
>
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