Well, in precise machine control, there are systems which use SRM motors in
the range of 400V, 500A which offer phase accuracy of about 10um at speeds
of 10m/s.
Does that make them AC servo motors or BLDC motors?
And as for "flat-topped sine wave, are you sure it is NOT a space vector
wave? When I did SVPWM on PIC18F452 some 6 years ago, it made a lovely sine
wave measured from phase to phase, but a single phase to neutral was still
looking like a hybrid between sine and trapese wave, with a notch in the
middle. But that is because space vector modulation works exactly that way,
giving you latger phase to phase voltage amplitude with the same common
supply voltage. And indeed, SVPWM in full overdrive mode is the trapese
wave!
Anyway, the scooter in the pdf is something I would love to drive!
On Thu, Nov 11, 2010 at 1:30 AM, Peter C. Wallace <p...@mesanet.com> wrote:
> On Wed, 10 Nov 2010, Brian wrote:
>
> > Date: Wed, 10 Nov 2010 00:00:29 -0500
> > From: Brian <turbo94must...@gmail.com>
> > Reply-To: EMC developers <emc-developers@lists.sourceforge.net>
> > To: EMC developers <emc-developers@lists.sourceforge.net>
> > Subject: Re: [Emc-developers] BLDC Driver
> >
> > BLDC and AC servos are not the same. The difference is subtle, and
> > they could be interchanged for one another, but would not result in
> > optimal operation. the difference is the shape of the back EMF
> > voltage they generate. The AC motor will tend to generate a more sine
> > like EMF, and the DC motor will tend to generate a more square, or
> > trapezoid like shape.
>
>
> Actually theres very little difference. All the PMSMs I've seen generate
> somewhat flat topped sine wave BEMFs, this include 2 phase CPU fans (BLDC),
> AC
> servos, washing machine motors etc. For example the Parker motors we are
> using
> for 8I20 testing are specified for either trapezoidal drive or sinusoidal,
> they dont care...
>
>
> >
> > This guy from MIT has a lot of good info he has written on the subject
> > http://scolton.blogspot.com/
> >
> > Specifically this paper here.
> > http://web.mit.edu/scolton/www/3phduo.pdf
> >
>
> Simulated waveforms... Ha Ha
>
> > Brian
> >
> >
> > On Tue, Nov 9, 2010 at 1:16 PM, Andy Pugh <a...@andypugh.fsnet.co.uk>
> wrote:
> >> On 9 November 2010 17:25, Brian <turbo94must...@gmail.com> wrote:
> >>>
> >>> If you use PWM, doesn't that make it an AC motor?
> >>
> >> It's fuzzy. BLDC motors are also known as AC servo motors.
> >> To further muddy the waters, one potential use of the generalised BLDC
> >> component would be old-school VFD or new-fangled flux-vector drive of
> >> induction motors (if they have encoders).
> >>
> >> --
> >> atp
> >>
> >>
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> Mesa Electronics
>
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