NAH, not correct.
I looked at one of the mentioned manufacturers, and the actual data from
them was 86% for a good marine app.
((
Marine app wants low rpm, high torque, ie 1800 rpm is much better than
3600 rpm.
An ideal marine motor is 400 rpm to 1000 rpm, with a large diameter prop
(3 sizes up from comparable ice).))
The best, peak, efficiency for one case was 92%, iirc from the mentioned
manufacturers. I was impressed.
Still, Quoted-peak for one case at 92% does not mean, at all, that "they
are all" 93%.
It also does not mean that the system is 92%, for you, installed.
So a quoted-best-case of 86% might actually be about 80-82% for you,
installed, in the real world.
(Contactors create losses. Cabling. Isolation switches. Temperature. etc..)
Technically, anything brushless using a method, any method, of precisely
knowing the angular position of the motor will always be better than
relying on brushes and a fixed "advance".
AC Servo motors for example use an optical encoder, and "twisted"
laminations of fairly small angular section.
The smart part comes from knowing "in advance" where to direct most of
the power, and taking into account current load, lag, and
desired-position via "commanded-position" in the PID loop.
This allows very, very, very accurate tracking of the commanded
position, upto about 10/10.000 counts = 1/1000 of one rev, or less than
0.3 degrees max worst-case error.
On 22/07/2016 08:39, fitloose wrote:
>
> I don't why folk say brushless always beats brushed. It's simply not
> always true. The Saietta, Lynch, AGNI, and all the variants that came
> after Cedric Lynch's motor design are all around 93% efficient. I can
> show you plenty of brushless that get nowhere near that and expensive
> ones like Parker Hannafin that better. Comes down to what you want.
>
>
> John R.
--
-hanermo (cnc designs)
Posted by: Hannu Venermo <gcode.fi@gmail.com>
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