On Thu, 13 Aug 2009 06:55:36 -0700, Rob G wrote:

Thoroughly recommend these inverters - once you've gone up the required
learning curve they really are great for running a 3 ph motor at
variable speed.

On a related note I've just got into electric radio control planes again
after a long break - they now use 3ph AC brushless motors instead of the
old brushed DC jobs. The on-topic bit is that they now have tiny
electronic speed controllers which don't have the problems DC controllers
had - since they are only effectively PWM switching three sets of DC to
get the 'phases' the controller itself needs no heatsinking and uses very
little power.

If anyone needs a small motor with very high power/weight (150W from a
1.5" diameter 1" end to end motor, up to 1KW or so if you want) with a
simple speed controller then they are well worth a look.

The electronic speed controller (ESC) takes RC servo control signals, but
that's basically a variable length pulse train - you can get 'servo
testers' which would just give you a knob to twist. And any number of
microcontroller boards will drive them directly...

The ESC is programmable as well - several levels of soft starting, motor
braking, low battery protection etc etc. And no end of gearboxes, toothed
belt drive pulleys etc. available if you need them.

I'll shut up now. ;-)