Title:
LAMINATED MAGNET CORE
United States Patent 3624576
Abstract:
A laminated magnet core for contactors and the like has a working airgap. The magnet core is made up of a stack of metal sheets having respective slitlike openings extending across a portion of the width of the sheets. The openings overlap and jointly form a slot extending transversely through the core. At least one perforated ferromagnetic sheet extends into the slot for reducing the magnetic effective width of the slot so as to define a remaining gap for reducing the core remanence and for reducing core losses in said core.
Application Number:
05/069002
Publication Date:
11/30/1971
Assignee:
Siemens Aktiengesellschaft (Berlin and Munich, DT)
Other Classes:
335/297, 336/234
International Classes:
H01F7/08; H01F7/08; (IPC1-7): H01F3/00
Field of Search:
335/227,281,297 336
Primary Examiner:
Harris G.
Claims:
I claim
1. A laminated magnet core for contractors and the like having a working airgap, the magnet core comprising a stack of metal sheets having respective slitlike openings extending across a portion of the width of said sheets, said openings being at least partly overlapping and jointly defining a slot extending transversely through said core, and at least one perforated ferromagnetic metal sheet extending into said slot for reducing the magnetically effective width of said slot so as to define a remaining gap for reducing core remanence and for reducing core losses in said core.
2. In a magnet core according to claim 1, said perforated ferromagnetic sheet being dimensioned and curved so to be held self-tensioned in said slot against the edges of said openings defining said slot.
3. In a magnet core according to claim 1, said ferromagnetic metal sheet having a plurality of stamped out slitlike perforations.
4. In a magnet core according to claim 3, said perforations having respective longitudinal axes, said perforations being disposed in said ferromagnetic metal sheet so that said longitudinal axes are perpendicular to the longitudinal axis of said slot.
Description:
My invention relates to laminated magnet cores made up of stacked metal sheets, especially U-shaped magnet cores for contactors and the like. More particularly, my invention relates to laminated magnet cores where ferromagnetic means are provided to reduce core losses.
The invention is related to those disclosed and claimed in the copending applications of G. Bohlke, Ser. No. 69001, filed Sept. 9, 1970, claiming a German priority of Jan. 28, 1970; and O. Muller and G. Rauter, Ser. No. 69003, filed Sept. 2, 1970, claiming a German priority of Sept. 4, 1969, these applications being assigned to the assignee of the present invention.
Copending application Ser. No. 69003, discloses a U-shaped magnet core made up of laminated metal sheets having respective openings therein which jointly define a slot extending transversely through the core. And, according to one embodiment thereof, a ferromagnetic part is disposed in the slot.
It is an object of my invention to secure a reduction of core losses in the type of laminated magnet cores discussed above.
It is another object of my invention to prevent an undue high heating of the ferromagnetic part in laminated magnet cores of the kind referred to above.
According to a feature of the invention, additional losses of the above referred to laminated magnet cores are avoided by means of the inserted ferromagnetic part provided the latter comprises one or more perforated metal sheets as required by the invention. With such one or more sheets, it is possible to prevent undue high heating of the same. It is especially advantageous if the perforations are formed as stamped-out slitlike openings. The eddy currents are especially effectively prevented if the openings are disposed such that the longitudinal axes thereof are perpendicular to the longitudinal axes of the slot extending through the magnet core, that is perpendicular to the direction along which the perforated sheet is inserted into the core.
The invention will now be discussed with reference to the drawing wherein:
FIG. 1 illustrates a U-shaped magnet core and a perforated metal sheet extending into a slot in the core body, the sheet being perforated as required by the invention;
FIG. 2 illustrates another embodiment of the perforated metal sheet of the invention; and
FIG. 3 illustrates a portion of the bight of the U-shaped magnet core of FIG. 1 together with a perforated ferromagnetic sheet that is curved and dimensioned so as to be held in the slot of the core under tension, the sheet being tension braced against the edges of the slot.
The magnet sheets of magnet core 1 are designated by reference numeral 2. Openings 3 are formed in the sheets 2 by stamping and are disposed in the sheet so as to be symmetrical with the centerlines of the individual sheets. The bridging or carrying portions of the sheets 2 are designated by reference numeral 4. The stamped out openings 3 of the individual sheets 2 overlap in mutual alignment and jointly define a slot extending transversely through the magnet core for accommodating a ferromagnet part in the form of a perforated sheet 6 therein. The perforated sheet 6 is shown in FIG. 1 as extending partially into the slot and has, preferably, a length that corresponds to the width of the magnet core 1. The perforated sheet 6 has slitlike stamped-out openings 7 having respective longitudinal axes perpendicular to the direction of the insertion of sheet 6 into the slot of core 1 or perpendicular to the longitudinal axes of the slot. The perforated sheet 6 affords the possibility of interrupting especially many eddy current circuits.
The perforated sheet 8 according to FIG. 2 is similar to the sheet 6 except that here the slitlike stamped out openings 6 are substituted by circular-shaped holes 9. The perforated sheet 8 is simple to produce in accordance with the methods of stamping technology and prevents the occurrence of eddy currents with practically the same effect as does the sheet 6. The stamped-out openings 7 and 9 in the sheet 6 and 8 respectively can be varied as desired, however, attention must be given to insure that eddy currents are eliminated to the greatest extent possible.
The airgap in the magnet core required to reduce core remanence can be produced in simple manner since the width of the openings 3, for example, can be selected to have a size larger than 0.6 millimeters so that they can be stamped with the conventional tools. Compared to known arrangements wherein the magnet core parts are put together from separate magnet parts, the rigidity of the magnet core of the instant invention is substantially improved by means of the bridging or carrier portions 4, so that in almost all instances, the cover plates associated with known magnet cores can be eliminated. In order to preclude a lateral displacement of the perforated sheets in the slot of the magnet core when cover plates are not used, the perforated sheets 6 and 8 can be provided with a curvature, so that they are held in the slot of the core under tension, the sheet being tension braced against the edges of the slot. Or, the sheets may be secured with glue, or they may be secured by adding a castable material in order to insure in an advantageous manner their permanent fixation in the required position in the slot.
The practical operation of the magnet core equipped with a perforated sheet has shown that practically no heating of the sheet results by occurring eddy currents.
Upon a study of this disclosure it will be apparent to those skilled in the art that my invention permits of various modifications and uses and consequently may be given embodiments other than particularly illustrated and described herein, without departing from the essential features of our invention and within the scope of the claims annexed hereto.