Magnetic fluid seal of rotation shaft is a kind of non-contact seal, with a closed magnetic circuit consisted by a ring permanent magnet, magnetic pole shoes
and a magnetic rotation shaft.
Unlike standard BLDC motors, the magnetic field isn't reinforced at the pole shoes
and there is no cogging torque.
As shown, in these generators there are PMs between two adjacent pole shoes
. The PMs are located in the leakage flux paths, not in the main flux paths.
Its authors apply the MWFTh equations only to the small air gap above the pole shoes
(see Equation (24) in page 414 of ), adding thereafter, in the same page, that the contribution of the slots and the area outside the poles (saliency) has to be taken into account (if only necessary) by means of special techniques.
The construction of PM poles may be designed with or without ferromagnetic pole shoes
. In this paper distribution of the magnetic field caused by PM poles both with and without ferromagnetic shoes has been studied.
Tooled with simple pole shoes
and other modular components, magnetic chucks can hold odd-shaped parts.