Hej Sean H. Breheny. Tack f=F6r ditt meddelande 01:29 2002-08-06 enligt=
 nedan:
>Morgan is right, they apparently do expect you to tristate each phase for=
 part of its cycle
>(actually, this would be roughly the same as setting it to half voltage
>since the wye neutral point sits around half voltage anyway, and this
>happens when the back emf for that phase is near zero).

I don=B4t think it is the same at all.  "Tristateing" Freewheeling it as i=
 say, i mean shut of both transistors and let the inductance shoot current=
 through the freewheeling diodes you should have across the transistors,=
 regaining some current to the power supply / battery / other pahse drivers=
 / other electronic devices.

I think holding it to zero will only turn that energy to heat in the motor,=
 plus occasionally give a negative momentum.

Also: Driving all phases strong, will probably induce lots of corrent in the=
 windings.  The system is "overdefined" if driving more than two pases=
 concurrently.  Ot works if you drive each with sinus 120=B0 apart.

I once put a scopte to a large brushelss fan, and what i saw was:
When the transistor shut off, the voltage wol go to opposite state, making=
 current flow in the other transistors parrallel diode for a short while,=
 then it will fall back to an EMF induced voltage (with some ringing)

Hum... with an A/D and some clever algorithm this could be used to drive the=
 motor without the hall sensors...?

/Morgan

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