Comparative Analysis of Different Box Inductor Designs

Generally, in non-isolated power converters, the highest temperature is reached in inductors and switching devices due to power losses. Extracting heat is always challenging, requiring a careful three dimensional (3-D) design and bulky heatsinks. For inductors, this challenge can also be addressed using custom magnetics; the shape of inductors could be designed aiming to decrease the reached temperature. In this work, a detailed study of new 3-D coils termed "Box inductors" has been carried out. The advantage of this new structure is that it has a large surface area for a given volume, which allows a better heat transfer and, thus, a decrease in temperature. This "Box inductor" is used in a single-phase single-stage transformerless inverter integrating the intermediate energy storage. Three Box inductor designs with the same PLT-3C95 core, but with different types of geometries are compared, which are also compared with a conventional RM14/I-N87 coil to establish which one leads to lower losses and temperature. Matlab and Maxwell are used to accurately estimate the losses. Prototypes of the three designs are built and tested, and the results of inductance value, losses, and temperature are compared.