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DEVICE DESIGN AND FABRICATION 4.5 kV 120 A SICGT with a chip size of 8 mm x A. SICGT and Diode 8 mm and a new high heat resistive resin capable of Fig. 1 shows a cross-sectional view of the 400°C operations were developed. The SICGT developed SICGT. A p buffer layer was grown to coated with the resin has a low leakage current of reduce the excess carrier injection from the n+ less than 5 x 10 6 A/cm2 at both 4.5 kV and 250 0C, emitter, and an n+ buried gate was introduced to a low VF of 5.0 V at 120 A, and short turn-on and reduce a storage time. SICGT has a low storage turn-off times of 0.3 [ts and 1.7 [ts respectively. time, a low gate parasitic inductance, a low turn-off A SICGT module was built by mounting one gain (less than 1) and a snubberless turn-off SICGT and two 6mm x 6mm SiC pn diodes in a operation, which differentiates SICGT from SiC metal can package, and a 110 kVA PWM 3 phase GTO. Because of these advantages, SICGT can inverter was developed by using six of the SICGT achieve lower power losses than SiC GTO. In order modules. The electric power capabilities of both the to achieve the high blocking voltage, BV, a p-bases developed SICGT and the 3 phase inverter are the with low impurity concentration of 1-2 x 104cm-3 largest ones among the reported SiC switching and thickness of 75 ptm was used. Furthermore, a devices and SiC inverters, respectively. mesa JTE [10] is used as a termination structure, which was formed by ion implantations.

We have carried out analysis of lightning surge on overhead distribution lines by means of EMTP. We made a model for electric breakdown of a 14‐m concrete pole with impulse voltage (rise time: 2 μ s) applied to the outer surface at the top of the concrete pole. We found that the transient impedance of the breakdown increased linearly before the breakdown and decreased exponentially after the breakdown. The measured voltage and current waveforms correspond to the calculated waveforms by regarding the impedance of the breakdown as resistance. Also we examined the impedance of flashover of an insulator with impulse voltage applied to the lines. The transient impedance of flashover is expressed approximately by the formula: Z(t) = A × exp(−(t − t0)/τ) (A = 1500 to 5000, τ = 3 × 10−8 to 5 × 10−8 s, t: time, t0: starting time of flashover). © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(1): 34–41, 2005; Published online in Wiley InterScience (http://www.interscience.wiley.com). DOI 10.1002/eej.20022

Highly water-dispersible flake-like titanophsphate nanosheets were synthesized by one-pot process controlling the acid–base reactions between Ti species, phosphoric acid, and the hydroxides of bulky cations in very weakly basic aqueous sols.

SUMMARYWe have carried out analysis of lightning surge on overhead distribution lines by means of EMTP. We made a model for electric breakdown of a 14-m concrete pole with impulse voltage (rise time: 2 µs) applied to the outer surface at the top of the concrete pole. We found that the transient impedance of the breakdown increased linearly before the breakdown and decreased exponentially after the breakdown. The measured voltage and current waveforms correspond to the calculated waveforms by regarding the impedance of the breakdown as resistance. Also we examined the impedance of flashover of an insulator with impulse voltage applied to the lines. The transient impedance of flashover is expressed approximately by the formula: Z(t) = A × exp(-(t -t 0 )/τ) (A = 1500 to 5000, τ = 3 × 10