RC India

This is directed at the electrical wizards amongst us...

can I drive a brushless motor if I connect it to three phase AC ???
provided I keep the voltage appropriately low

A brushless motor can be destroyed by direct connection with battery only if we connect it with a battery which can supply more current than its stall current and for a time more than 10 sec.or as stated by motor manufacturer..
ur motor can not be ruined by 80mah motor..
it can not supply large current to destroy motor..

Of course not ! Our motors are not AC motors. They are BLDC - Brushless DC motors. They still require a DC power source. The ESC just does the work of replacing the brushes.

I think we can, it will be little hard to start but should run fine after a flick.

ofcourse we can run! only on 3 phase AC provided voltage maintained at specified range!(may be you can use Variac)
our RC (outrunner or Inrunner ) motor are nothing but miniature AC Induction motor! our ESC does the job of Inverting DC into AC! in simple words it converts DC into 3 phase AC with variable frequency and voltage! and its not doing job of brushes,Its doing job of Slip rings or Commutator
Hope this helps!

Sorry but  induction motors do not use permanent magnets.. And ALL the motors used on models, that I have seen, do have them.

There ARE brushless induction motors though, but not for our application.

 :iagree: but it can still run on 3 phase AC.

It can run only if the 3 phase AC has the right timing w.r.t to the rotation of the magnets. Sushil bai is correct.

Induction type motors do not have magnets and as the name says they create the magnetic field by virtue of electrical induction. So, these induction motors do not need accurate timing.

In BLDC motors (that we use for RC flying) have perm magnets and they need to "align" properly with the rotating magnetic field produced by the ESC. This is where timing comes in. The ESC senses the magnet positions by monitoring the back-emf generated from the coils and produces the right drive required.

So, connecting the BLDC to a 3 phase (reduced voltage of course) might not work as the way you wanted. However, you may see the motor singing a tune or moving in a haphazard manner.

I believe it will stutter initially but if you give it two three turns with your hand, it will catch a phase and start running smoothly. It would be so cool if someone with access to three phase supply and a variac can try this  (:|~

Without the position sensing of the magnets, its just pure luck to get it running smooth. The moment the load conditions change.. even a tiny bit.. the motor is off sync. BLDC esc is a closed loop design.