Abstract: A device comprising a plate (1) for holding workpieces (11) when handled on a machine tool, and a magnetic field excitation unit which is made in the form of at least one magnetic core (3) mounted on a base (2). A bottom portion (4) of each of the cores (3) is encompassed by a direct-current coil winding (6) and is thickened so as to form, together with the top portions (5), a step for the plate (1) to rest upon. The top portion (5) is accommodated in the interior of the plate (1) and is magnetically insulated therefrom with the aid of elements (7) made of a nonmagnetic material. The area of contact of the plate (1) with the core (3) does not exceed the cross-sectional area of the plate (1) confined within the perimeter of the step of the core (3), while a distance (.tau.) between the axes of the cores (3) is determined by the following relationship: ##EQU1## where B is the magnetic induction corresponding to the magnetic saturation of the material of the plate (1);h is the thickness of the plate (1);P.sub.

Abstract: The annular cavity in the stator of a cryogenic electric machine is defined by the housing and by the cylindrical element holding the winding. An electrically non-conducting ferromagnetic liquid is introduced into the annular cavity and is permitted to flow therein. The ferromagnetic liquid also serves as a cooling liquid for the cryogenic electric machine. A cooling system is connected to the annular cavity and together they form a closed loop for the circulation of the ferromagnetic liquid. Axial ribs are provided on the inner surface of the housing to prevent rotation of the ferromagnetic liquid as it flows inside the annular cavity.