BCC: Peter - comment welcomed.

> Anyway, just came across some videos on YouTube about using a car alterna=
tor as a sort of bldc motor, as any of you tried this before? It seems like=
 a very neat thing to try... =A0Any results that you may want to share? I a=
m curious about speed and torque possible with one of these.

Please provide some links to videos etc that you consider pertinent.

A car alternator has in the vast majority of a rotor  which is excited
via brush feed. That makes it non-brushless to start as is.

When the device is an alternator the 'field'  is a rotating magnet and
the power input is via shaft mechanical drive and the brushes need
transfer only field power so brush needs are far lighter than for
power feed via brushes. Rotor is usually fix magnetised in polarity so
DC feed via sliprings rather than a commutator can be used.

For the device to be a motor if the rotor is still a rotor (and not
clamped with stator as rotor as is done for some re-applications) then
rotor can still be a brush fed "DC" magnet. Stator coils now have
rotating field applied at full power and system should be able to be
made to work OK.  This is NOT brushless but it uses sliprings and not
commutator and electrical energy transfer to rotor is small % wise.
Effiiciency needs to account for DC magnet drive but should be able to
be "OK" [tm].

If the rotor is re-fitted to have permanent magnets (as is sometimes
done for alternator applications) a true BLDC can be produced.
Efficiency seems likely to be similar to other implementations.

I've copied this to a man who actually knows the real answer and it
will be interesting to see what he says :-).


              Russell

--=20
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