2020-12-24 18:43 skrev andy pugh:
On Tue, 22 Dec 2020 at 16:37, Nicklas SB Karlsson <[email protected]>
wrote:
As I understand it is an IPM Internal Permanent Magnet motor, have
principal picture in old course literature from university. Would
guess
it is used because full torque is seldom used and iron losses will be
lower for lower magnetic losses
The video suggests that by changing the phase of the magnetic field
relative to the rotor they can effectively switch between reluctance
(for high speed, low back-emf) and PM (high torque) modes.
Reluctance is much higher in path of magnets so it is much easier to
increase flux in between magnets there it is iron which have much lower
less Reluctance. Never heard about increasing flux for IPM, only
flux-weakening to run at higher speed. To get reluctance effect there
should be flux between magnets, uncertain about this, have a tried a
reluctance motor, it had two operating points, one rotating backwards at
slower speed less efficient.
For those not familiar with magnetic circuits reluctance fulfill same
purpose in magnetic ciruits as resistance do in electric circuits though
circuits are less perfect, in particular I do not think there are any
insulator, only conduct magnetic flux better than vacuum. Magnetic
fields are generated by currents or magnets, then flux depend on
magnetic field and reluctance=1/permeance.
If I think right the motor will have higher inductance in between
magnetics and this will increase cross coupling which vill make it
harder to keep magnetic flux on desired level.
Nicklas Karlsson
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