We have developed a loss estimation method that is applicable to three-phase ac reactors using amorphous cores in a 400-kVA UPS. The method is based on measured the B-H curves and iron losses of the cores, modeled with magnetic simulations of a finite-element method considering the directions of the amorphous ribbon planes. The reactors are formed from wound cores. Two types of magnetic legs are proposed: structure A, toroidalshaped with slits, and structure B, sector prism-shaped cut from a wound core. Their unit volumes are shrunk by 9% and 19%, respectively, compared with that of a conventional silicon-steel core reactor. Both reactors have about half the total losses of the conventional silicon-steel core reactor, resulting in increased UPS efficiencies of up to 0.55%. The calculated iron losses at the pulse width modulation (PWM) carrier frequencies agree with measured losses within 10%. The accuracy of the loss estimation method for PWM-induced reactors is discussed. The method is confirmed to enable accurate design of a reactor for filtering in a high-efficiency inverter system.
A 1OW class thin type D C D C converter is developed which uses a new type coreless wire transformer. The converter is intended for portable equipment use. The coupling factor of the wire transformer is more than 95% at frequencies higher than 1OOkHz. When applied in a 3 output DCDC converter, the converter is only 5 . 5 m thick and has 70% efficiency.
Abstract-This paper presents an analysis of characteristics of multiphase buck converters with coupled inductors. We derive equivalent inductances that provide both low per-phase steady-state ripple current and fast transient response. The characteristics of coupled-inductor circuits -low per-phase ripple current and fast response -were examined and verified by circuit simulation and experiments.
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