Magnetic performance of step-lap joints in distribution transformer cores

The magnetic characteristis of cores with step-lap joints are analyzed by using the finite element method taking into account eddy current and magnetic saturation. The effects of the following factors on the magnetic characteristics such as flux and eddy current distributions and magnetizing current are clarified quantitatively. 1)step-lap length 2)length of air gap at the joint 3)number of laminations per one stagger layer 4)flux density (magnetic saturation) Obtained results give useful suggestions improving the design of the joints of transformer cores.