On Friday, August 27, 2021 at 5:38:01 AM UTC-7, Tom Del Rosso wrote:
> Jeroen Belleman wrote:
> > On 2021-08-27 08:07, Tom Del Rosso wrote:
> >> Jeroen Belleman wrote:
> >>> On 2021-08-26 04:25, Tom Del Rosso wrote:
> >>>> Jeroen Belleman wrote:
> >>>>> Tom Del Rosso wrote:
> >>>>>> AIUI you use iron cores for low frequency and ferrite for high
> >>>>>> frequency because ferrite doesn't get magnetized, so why couldn't
> >>>>>> aluminum do the same?
> >>> The short answer is that aluminium is worse than nothing as a
> >>> transformer core. It *will* fight changing fields.
> > Aluminium is a good conductor. There will be eddy currents induced
> > in it that will oppose any /change/ of magnetic field. Lenz law and
> > all that.But once external fields are removed and enough time has
> > passed for eddy currents to decay, there will be no field left over.
> I know what you mean, but since the current only has the length of the
> core to travel it's hard to grasp how that produces more than a very
> short pulse.
The problem that a core solves, is flux coupling in multiple windings. The
magnetizability of a core means that it contains and directs almost all the magnetic flux.
A conductor will exclude flux, which is counterproductive; even the conductivity
of iron is detrimental (so lamination, or iron powder, or nonconducting ferrite is
In induction motors, where the flux is intended NOT to change in the rotor (so the
alternation of current rotates the rotor instead of changing its magnetization) there
are aluminum parts to enhance the available torque.
When/if you don't allow the rotor to move, those rotors burn up. Almost all induction motors have
thermal protection components that open if/when the motor is stalled.