In a three-phase and three-leg core structure of a core-type transformer comprising three main legs of a substantially circular cross-sectional shape and a yoke of a non-circular cross-sectional shape for magnetically connecting the three main legs, each of the three main legs having a cross-sectional area substantially equal to the cross-sectional area of the yoke, wherein at least joints between the steel plate laminations of a center main leg and the adjoining steel plate laminations of the yoke are in a mitered oblique joint without requiring the shearing of the ends of the steel plate laminations, and the edges of the leg and yoke laminations at which edges the oblique miter joints are formed approach each other in length.
A three-phase and three-leg core of a core-type transformer comprising three main legs formed of a plurality of steel sheets stacked in the form similar to a circle in cross section and spaced each other, and upper and lower yokes formed of a plurality of steel sheets stacked in the form similar to a circle in cross section for magnetically connecting the main legs. The steel sheets for forming each main leg are cut diagonally at opposite longitudinal ends thereof, and each yoke is formed of two types of steel sheets, one type being of diagonal cuts disposed at opposite longitudinal ends thereof to provide steel sheets of the trapezoidal shape and the other type being of a diagonal cut disposed at one of opposite longitudinal ends thereof and a right angle cut disposed at the other longitudinal end thereof to provide steel sheets of the trapezoidal shape. The steel sheets for forming the upper and lower yokes have a width greater than the width of the steel sheets for forming the main legs. The opposite longitudinal ends of the steel sheets for forming the center main leg are cut diagonally at an angle less than 45 degrees and joined diagonally and at a right angle to the steel sheets for forming the upper and lower yokes through the entire surfaces. The steel sheets for forming the two outer main legs are cut diagonally at opposite longitudinal ends thereof at 45 degrees and joined diagonally to the steel sheets for forming the upper and lower yokes in an area in which the yoke steel sheets are cut diagonally. This construction is conducive to reduced iron loss and to form the main legs of a small diameter.
Electric machine, such as a transformer, a choke or a constant-voltage regulator, having an iron core assemblable from a plurality of individual, substantially rectangular core parts, including legs and intermediate yoke parts, formed of mutually held-together laminate layers, and clamping means such as clamping straps or plates clampable into engagement with a corresponding clamping surface at outer contours of the leg core parts transversely to the laminate layers by clamping elements such as screws or rivets, includes means defining channel or tunnel-shaped recesses extending parallel to all of the mutually parallel laminate layers of all of the assemblable individual core parts and substantially perpendicularly to juxtaposed joint abutments of the respective individual core parts.
A stepped iron core formed of sheetmetal laminations for a static or dynamic electric machine, such as a transformer, having yokes and legs and intermediate parts of at least one thereof including stacks of the sheetmetal laminations mutually held together forming individual steps of the yokes and the legs, the yoke stacks and the leg stacks being joinable with one another at respective abutment joint locations formed thereon, and means located at the respective abutment joint locations for achieving a varying magnetic reluctance therebetween so that a longer path of lines of force passes through the respective abutment joint locations in the region thereof of lower magnetic reluctance.
