High-Frequency Gap Losses in Nanocrystalline Cores

Finite element analysis is used to examine the gap losses that occur in finely laminated nanocrystalline inductor cores under high-frequency operation. The losses are seen to be concentrated in the region of the air gap and the dependence of the losses on key design parameters and operating conditions is explored. The results show that gap losses can be significant in this type of core, creating hot spots around the gap, and the losses are not accurately predicted by established design equations for low-frequency laminated cores. A modified loss equation is proposed. Validation is provided by measurements on a 300-A, 60 kHz inductor.