Abstract: A transformer core is made by winding a strip of ferromagnetic material, such as amorphous metal or silicon iron, on a winding mandrel to form a first annulus and cutting once through this annulus to create a plurality of individual laminations which are then assembled in packets about a nesting mandrel of a smaller diameter than the winding mandrel to form a second annulus. Each packet consist of a predetermined number of groups of laminations, with the ends of each lamination group lapping each other to form a lap joint. The lap joints of each packet are arranged in staggered positions to create a repeating step-lap joint pattern confined within a predetermined joint region. By decreasing the lap joint dimension and increasing the number of groups in successively assembled packets, the increase in build of the joint region over that of the remainder of the second annulus is minimized. The completed transformer core uniquely characterized by its variable lap joint dimension and the absence of short sheets.

Abstract: This trip device comprises a permanent magnet of cobalt-rare earth material and a plunger which is normally held in a withdrawn position by the permanent magnet. A tripping coil surrounds the plunger and, upon energization, develops tripping flux that opposes the holding flux from the permanent magnet, thereby to effect release of the plunger. In a position between the tripping coil and the permanent magnet, flux-diverting structure of highly permeable magnetic material is provided for shunting a portion of the tripping flux through a shunt path bypassing the permanent magnet. This shunt path contains a relatively large non-magnetic gap for limiting the tripping flux through the shunt path sufficiently to cause 30 percent or more of the tripping flux to pass through the permanent magnet in a direction opposite to the direction of the holding flux.