Can I run a "brushless DC FAN" backwards?
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From: Grant on 4 Aug 2010 18:51 On Wed, 04 Aug 2010 11:50:00 -0400, John Ferrell <jferrell13(a)triad.rr.com> wrote: >http://www.gobrushless.com/kb/index.php?title=FAQ >http://www.castlecreations.com/ > >The intervention must be performed between the actual motor and >controller. The above links are the shallow and deep ends of the >brushless pool for Radio Control model airplanes. Note the prices on >the Castle controllers! > >I suppose it could be that there are motors called brushless that are >not three phase devices. Common fan motors are two phase, sometimes on applied power they kick a bit before spinning. One 4 pin Hall effect with complementary outputs, or simple 3 pin Hall plus a transistor inverter. Pulse output (tacho) is another open collector transistor hanging off the Hall device. > >Swap any two MOTOR wires! True for three phase, swap the Hall drive for two phase, I already posted that. > >> >>But "muffin" fans generally have the controller built-in. IF they >>have a third wire it's for speed sensing. Yes, but the controller just senses the magnet (on rotor) position, thus is a simply a Hall device with or plus an inverter for the other coil. Better class motors for say CD spindle drive, have three Halls for feedback (couple I dismantled recently had that. So do the slow floppy spin motors, but they have an extra magnet and Hall outside the rotor for (I guess) the Index pulse. These motors had three phase drive to stator coils. >> >> ...Jim Thompson >John Ferrell W8CCW Grant.
From: Nobody on 4 Aug 2010 18:54 On Wed, 04 Aug 2010 11:50:00 -0400, John Ferrell wrote: > I suppose it could be that there are motors called brushless that are > not three phase devices. PC fans are 2-phase.
From: John Ferrell on 5 Aug 2010 11:16 Sensors are no longer used with the current technology. The controller does it all. On Thu, 05 Aug 2010 08:51:31 +1000, Grant <omg(a)grrr.id.au> wrote: >On Wed, 04 Aug 2010 11:50:00 -0400, John Ferrell <jferrell13(a)triad.rr.com> wrote: > >>http://www.gobrushless.com/kb/index.php?title=FAQ >>http://www.castlecreations.com/ >> >>The intervention must be performed between the actual motor and >>controller. The above links are the shallow and deep ends of the >>brushless pool for Radio Control model airplanes. Note the prices on >>the Castle controllers! >> >>I suppose it could be that there are motors called brushless that are >>not three phase devices. > >Common fan motors are two phase, sometimes on applied power they kick >a bit before spinning. One 4 pin Hall effect with complementary outputs, >or simple 3 pin Hall plus a transistor inverter. Pulse output (tacho) >is another open collector transistor hanging off the Hall device. >> >>Swap any two MOTOR wires! > >True for three phase, swap the Hall drive for two phase, I already >posted that. >> >>> >>>But "muffin" fans generally have the controller built-in. IF they >>>have a third wire it's for speed sensing. > >Yes, but the controller just senses the magnet (on rotor) position, >thus is a simply a Hall device with or plus an inverter for the >other coil. > >Better class motors for say CD spindle drive, have three Halls for >feedback (couple I dismantled recently had that. So do the slow >floppy spin motors, but they have an extra magnet and Hall outside >the rotor for (I guess) the Index pulse. These motors had three >phase drive to stator coils. >>> >>> ...Jim Thompson >>John Ferrell W8CCW >Grant. John Ferrell W8CCW
From: David Lesher on 8 Aug 2010 01:00 Cut the blades from the hub & glue back with opposite pitch. -- A host is a host from coast to coast.................wb8foz(a)nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
From: cbarn24050 on 8 Aug 2010 14:05
On Aug 2, 8:35 am, mike <spam...(a)go.com> wrote: > I have a project that needs reversible fans. > Can I make a brushless fan go backwards? Yes you can. > Is it as simple as swapping the leads on the coils? No it isnt. > Or is there more to it, like wrong phase for the magnetic pulse > into the hall device? You need to replace the controller. > > And then there's the question whether the blades will > move as much air running backwards. No they wont, much less in fact. > > The muffin fan is the ideal form factor for this job. > > Only other cost effective thing I can think to do is > put two fans in series and run either one. > > I really don't want to spend the money to buy reversible fans > even if they're available. I gots boxes of muffin fans. > > Ideas? Rethink your needs. > Thanks, mike |