Loss reduction of laminated core inductor used in on-board charger for EVs

A laminated core has advantages such as low loss, high permeability, and high saturation flux density. For inductor applications, an air gap has to be inserted into the magnetic circuit to avoid saturation at lower magnetic field strengths. However, when an air gap is inserted, fringing flux leaks out of the air gap and concentrates on the surface of the core. As a result, the iron loss increases to 292% compared with an ungapped structure, and the inductance characteristic deteriorates. Although a chamfered structure known as a prior art reduces the iron loss to 147%, there is room for improvement. In this paper, we propose a method for optimizing the shape of the air gap. Consequently, the proposed structure reduces the iron loss to 113% and improves the inductance characteristic. The proposed method helps increase the efficiency and reduce the size of the on-board charger.