![]() The coils are firstly wound on a former which has a cylindrical, rectangular or oval type cross section to suit the construction of the laminated core. Transformer Laminationsīut you may be wondering as to how the primary and secondary windings are wound around these laminated iron or steel cores for this types of transformer constructions. As the magnetic flux has a closed path around the coils, this has the advantage of decreasing core losses and increasing overall efficiency. ![]() This means that the magnetic flux circulating around the outer limbs of this type of transformer construction is equal to Φ/2. ![]() The advantage here is that the magnetic flux has two closed magnetic paths to flow around external to the coils on both left and right hand sides before returning back to the central coils. Shell type transformer core’s overcome this leakage flux as both the primary and secondary windings are wound on the same centre leg or limb which has twice the cross-sectional area of the two outer limbs. However, with this type of transformer construction, a small percentage of the magnetic lines of force flow outside of the core, and this is called “leakage flux”. The coils are not arranged with the primary winding on one leg and the secondary on the other but instead half of the primary winding and half of the secondary winding are placed one over the other concentrically on each leg in order to increase magnetic coupling allowing practically all of the magnetic lines of force go through both the primary and secondary windings at the same time. In the core type transformer construction, one half of the winding is wrapped around each leg (or limb) of the transformer’s magnetic circuit as shown above. In both types of transformer core design, the magnetic flux linking the primary and secondary windings travels entirely within the core with no loss of magnetic flux through air. The two most common and basic designs of transformer construction are the Closed-core Transformer and the Shell-core Transformer. Generally, the name associated with the construction of a transformer is dependent upon how the primary and secondary windings are wound around the central laminated steel core. These steel transformer laminations vary in thickness’s from between 0.25mm to 0.5mm and as steel is a conductor, the laminations and any fixing studs, rivets or bolts are electrically insulated from each other by a very thin coating of insulating varnish or by the use of an oxide layer on the surface. The resistivity of the steel sheet itself is high, thus reducing any eddy current loss by making the laminations very thin. These thin laminations are assembled together to provide the required magnetic path with the minimum of magnetic losses. ![]() In most types of transformer construction, the central iron core is constructed from of a highly permeable material commonly made from thin silicon steel laminations. One way to reduce these unwanted power losses is to construct the transformer core from thin steel laminations. These losses are due mainly to voltages induced in the iron circuit, which is constantly being subjected to the alternating magnetic fields setup by the external sinusoidal supply voltage.
0 Comments
Leave a Reply. |