| You are thinking of the old fashioned motor /speed controllers where
| they used a resistor. Today's modern units employ switching the
| turns the power on and off at a high rate, not much heating involved
| in this process.
Well, what he said is still correct about a brushed ESC -- it's most
efficient at 100% throttle, and less efficient at lower settings. Of
course, the difference is like 99% vs 95% or so -- not very
Brushless ESCs are always switching, even at full throttle, so I
wouldn't expect them to become more efficient at 100% throttle. One
reason for going brushless is that things overall tend to be more
efficient at partial throttle values than brushed systems, however.
| > Since I'm fairly new to - and more than a bit ignorant about - electric
| > flight, I'm curious about using more motor than one really needs. From
| > what I've read, one wastes battery power, turning it into heat by the ESC,
| > when at less than full power. Therefore, isn't it logical to use the
| > smallest motor one can use, commensurate with desired performance
That's the key right there ... `commensurate with desired performance'.
You may be right -- a motor+ESC might be most efficient at 100%
throttle (they often are, especially for brushed systems.) But if you
need 100% throttle to fly around, then that doesn't leave you much
extra power for playing around, and if your plane isn't fun to fly,
| > and run it at full power rather than installing a big motor and
| > running it at part throttle?
If you're looking to break a world duration record, absolutely. If
you're looking to just fly around and have fun, maybe not.
Also, that bigger motor weighs more, and that alone will make the
plane require more power to stay airborne.
If you're really interested in maximizing power system
(battery+ESC+motor) efficiency, get the `Electric Motor Handbook' by
Looks like it's been discontinued, so it might be hard to find.
It's a bit dated (for example, brushless motors only get a paragraph
or two, though most of the rest of the book applies to them too) but
it does a pretty good job of explaining things. It's also really
`dry' -- Boucher doesn't seem to be the best writer, but he does know
Doug McLaren, email@example.com
`Keep Cool, but Don't Freeze' -Hellman's Mayonnaise
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