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A Diode-Clamped Multilevel Inverter with Voltage Boost Function
Y. Sato,M. Kawasaki,T. Ito 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
Multilevel inverters are mainly used in high power and medium voltage applications to reduce the required voltage rating of the power semiconductor switching devices. On the other hands, these multilevel inverters are attractive for various applications regardless of the power ratings because they can essentially realize lower harmonics with lower switching frequency and lower electromagnetic interference (EMI). In this context, the multilevel inverters with larger number of levels suitable for circuit integration are actively investigated. Diode-clamped multilevel inverters are regarded as the promising solution. In the diode-clamped multilevel inverters whose number of the levels exceeds three, voltage balancing circuits for the DC capacitors to maintain the proper voltage are indispensable. The authors have been investigated the application of a circuit topology of the voltage balancing circuits so called Resonant Switched Capacitor Converters (RSCC). In the present paper, the utilization of the voltage boost function of RSCC to enhance the allowable range of the input voltage of the inverter is investigated. The voltage boost function is useful in the applications in which the DC source voltage is limited such as batteries and fuel cells. From the computer simulation and the experimental results, the usefulness and the operating characteristics of the voltage boost operation have been demonstrated.
A Basic Study on Chip Size Determination of MOSFETs to Minimize Total Power Loss
Y. Ikegami,H. Obara,Y. Sato 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
Chip area of power semiconductor devices is one of the key parameters to realize highly-efficient converters. In the case of MOSFETs, a larger chip area results in lower on-state resistance. However, switching loss and gate drive loss may become dominant due to increase in parasitic capacitances when the chip area is too large. Thus, the chip area must be determined adequately considering given operating conditions and characteristics of the devices. In this paper, relationship between the chip area and loss reduction effect in three different types of MOSFETs, that is, silicon MOSFETs, silicon-carbide MOSFETs, and super-junction MOSFETs, is investigated experimentally. From the results, it is clarified that each MOSFET has the optimum points of the chip area for the loss reduction depending on the switching frequency and current. A determination criterion of the optimum chip area is discussed on the basis of the theoretical calculation of the losses.
Sato, Y.,Iijima, T.,Adamczyk, K.,Aihara, H.,Asner, D. M.,Atmacan, H.,Aushev, T.,Ayad, R.,Aziz, T.,Babu, V.,Badhrees, I.,Bakich, A. M.,Bansal, V.,Behera, P.,Bhardwaj, V.,Bhuyan, B.,Biswal, J.,Bonvicini American Physical Society 2016 Physical review. D Vol.94 No.7
<P>We report a measurement of the ratio R(D*) = B((B) over bar (0) -> D*(+)tau(-)(nu) over bar (tau))/B((B) over bar (0) -> D*(+)l(-)(nu) over bar (l))where l denotes an electron or a muon. The results are based on a data sample containing 772 x 10(6) B (B) over bar pairs recorded at the Upsilon(4S) resonance with the Belle detector at the KEKB e(+)e(-) collider. We select a sample of B-0(B) over bar (0) pairs by reconstructing both B mesons in semileptonic decays to D*(-/+)l(+/-). We measure R(D*) = 0.302 +/- 0.030(stat) +/- 0.011(syst), which is within 1.6 sigma of the Standard Model theoretical expectation, where the standard deviation sigma includes systematic uncertainties. We use this measurement to constrain several scenarios of new physics in a model-independent approach.</P>
SEARCH FOR STRANGE TRIBARYON STATES IN THE 4He(STOPPED K-, p) REACTION
SATO, M.,BHANG, H.,CHIBA, J.,CHOI, SEONHO,FUKUDA, Y.,HANAKI, T.,HAYANO, R. S.,IIO, M.,ISHIKAWA, T.,ISHIMOTO, S.,ISHIWATARI, T.,ITAHASHI, K.,IWAI, M.,IWASAKI, M.,KIENLE, P.,KIM, J. H.,MATSUDA, Y.,OHNIS World Scientific 2009 International Journal of Modern Physics A Vol.24 No.2
<P> We have measured a proton energy from the stopped K<SUP>-</SUP> reaction on <SUP>4</SUP> He to search for strange tribaryon states at KEK 12 GeV PS. No statistically significant signal was observed in the missing mass spectrum obtained by the inclusive <SUP>4</SUP> He ( stopped K<SUP>-</SUP>, p) measurement. Upper limits of the formation branching ratio at the 95 % C.L. were derived for neutral tribaryon states with strangeness -1 to be (0.4 ~ 6) × 10<SUP>-4</SUP>, (0.2 ~ 6) × 10<SUP>-3</SUP> and (0.06 ~ 5) × 10<SUP>-2</SUP>/(stopped K<SUP>-</SUP>) for assumed natural widths of 0, 20 and 40 MeV /c<SUP>2</SUP>, respectively. </P>
Mesonic and nonmesonic weak decay widths of medium-heavy <tex> $ \Lambda $</tex> hypernuclei
Sato, Y.,Ajimura, S.,Aoki, K.,Bhang, H.,Hasegawa, T.,Hashimoto, O.,Hotchi, H.,Kim, Y. D.,Kishimoto, T.,Maeda, K.,Noumi, H.,Ohta, Y.,Omata, K.,Outa, H.,Park, H.,Sekimoto, M.,Shibata, T.,Takahashi, T.,Y American Physical Society 2005 PHYSICAL REVIEW C - Vol.71 No.2
Measurement of the lepton forward-backward asymmetry inB→Xsℓ+ℓ−decays with a sum of exclusive modes
Sato, Y.,Ishikawa, A.,Yamamoto, H.,Abdesselam, A.,Adachi, I.,Adamczyk, K.,Aihara, H.,Asner, D. M.,Aulchenko, V.,Aushev, T.,Ayad, R.,Bakich, A. M.,Bala, A.,Bhardwaj, V.,Bhuyan, B.,Bondar, A.,Bonvicini, American Physical Society 2016 Physical Review D Vol.93 No.3
<P>We report the first measurement of the lepton forward-backward asymmetry A(FB) as a function of the squared four-momentum of the dilepton system, q(2), for the electroweak penguin process B -> X(s)l(+)l(-) with a sum of exclusive final states, where l is an electron or a muon and X-s is a hadronic recoil system with an s quark. The results are based on a data sample containing 772 x 10(6) B (B) over bar pairs recorded at the gamma (4S) resonance with the Belle detector at the KEKB e(+)e(-) collider. A(FB) for the inclusive B -> X(s)l(+)l(-) is extrapolated from the sum of 10 exclusive X-s states whose invariant mass is less than 2 GeV/c(2). For q(2) > 10.2 GeV2/c(2), A(FB) < 0 is excluded at the 2.3 sigma level, where sigma is the standard deviation. For q(2) < 4.3 GeV2/c(2), the result is within 1.8 sigma of the standard model theoretical expectation.</P>