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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.

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A process technology for a pseudomorphic high electron mobility transistor (P-HEMT) with an offset-gate structure has been developed for millimeter-wave monolithic microwave ICs (MMICs). A HEMT with the offset-gate structure showed both reduced gate-to-drain capacitance and drain conductance compared with a device with a non-offset-gate structure. The device showed a maximum available gain (MAG) of 9 dB at 77 GHz. The device was applied to a 77 GHz three-stage power amplifier, which showed a small-signal gain of 16.5 dB. Under preliminary life testing, this amplifier showed a stable small-signal gain for over 160 hours of testing at 175°C.