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We analyzed the local behaviors of both time and space harmonic magnetic fluxes in this research to improve the efficiency of inverter-fed induction motors. As a result, we clarified that: the magnetic flux of time harmonics passes in parallel through rotor bars and the magnetic flux of space harmonics passes radially through the rotor bars from the delay side in the direction of rotation. We propose a new rotor slot structure to reduce harmonic losses by taking these results into consideration. We also manufactured a prototype that was applied to the proposed structure of rotor slots, and measured motor losses. Consequently, although the current was increased by 2%, the total loss under inverter driven condition in induction motor was reduced by 20% with the proposed structure under the equal output power of 1.1 MW.

We analyzed the local behaviors of both time and space harmonic magnetic fluxes in this research to improve the efficiency of inverter feeding induction motors. As a result, we clarified that: (1) the magnetic flux of time harmonics passes in parallel through rotor bars, and (2) the magnetic flux of space harmonics passes radially through the rotor bars from the delay side in the direction of rotation. We propose a new rotor slot structure to reduce harmonic losses by taking these results into consideration. We also fabricated a prototype that was applied to the proposed structure of rotor slots, and measured motor losses in experiments. As a result, the total loss in induction motor with the proposed structure was reduced by 20%.

A photodetector having a sensitivity only in a narrow-wavelength region has been fabricated by utilizing a thick semi-insulating GaAs (SI GaAs). Because the photon energy at the peak response is nearly equal to the bandgap energy of GaAs, this detector is called a band-edge-emphasizing photodetector. A theory is proposed to explain this phenomenon. Since GaAs is characterized by a short carrier lifetime and a steep change of the absorption coefficient, the active layer is assumed to be composed of two different parts connected in series, which are specified by a function delta . Good agreement has been shown between the experimental and the theoretical results on the sensitivity characteristics. >

A novel optoelectronic half-adder logic, composed of only two GaAs metal-semiconductor-metal photodetectors (MSM-PDs), is reported. The optoelectronic logic utilizes the features of the MSM-PD for both polarities of electrical bias (positive and negative). Without any other active devices such as transistors, the output delay time is short, less than 100 ps for the entire half-adder operation, which assures a very fast arithmetic operation. >

A metal‐semiconductor‐metal photodetector (MSM‐PD) fabricated on a semi‐insulating GaAs has a long wavelength response beyond the energy gap. It is enhanced by applying a second bias voltage to the bottom electrode. When the bias is 100 V, the responsivity exceeds the unit quantum efficiency, which indicates that a photoconductive amplification function exists. Since the dark current is as small as 0.2 nano‐amperes, it may be more suitable than an InGaAs or a Ge photodiode for long wavelength detection.