IEICE Electronics Express
Online ISSN : 1349-2543
ISSN-L : 1349-2543
Volume 20, Issue 4
Displaying 1-3 of 3 articles from this issue
LETTER
  • Yong Chang, Guangqing Bao
    Article type: LETTER
    Subject area: Electromagnetic theory
    2023 Volume 20 Issue 4 Pages 20220480
    Published: February 25, 2023
    Released on J-STAGE: February 25, 2023
    Advance online publication: January 23, 2023
    JOURNAL FREE ACCESS

    The primary aim of this study was to develop and validate an accurate sub-domain analytical model to estimate the magnetic field of electric machines with high-temperature superconducting (HTS) excitation and armature windings. The model was developed by utilizing the separation variable and harmonic analysis methods to solve Laplace’s or Poisson’s equations of the vector magnetic potential in two-dimensional polar coordinates. The theoretical derivations of the final analytical equations for the magnetic flux density distribution in the air-gap and in permanent magnets, electromagnetic torque, and no-load back-electromotive force (back-EMF) are explained in detail. Finally, the magnetic vector potential, flux density distribution of each sub-domain, no-load back-EMF, and inductive reactance of the armature winding were solved by considering the critical parameters of the superconducting materials, and the influence of higher harmonics. The finite-element method (FEM) was used to validate the accuracy of the developed analytical method for the investigated HTS generator. The results show the developed analytical method is accurate and time-saving.

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  • Lengkhang Nengvang, Shogo Katayama, Anna Kuwana, Kazufumi Naganuma, Ki ...
    Article type: LETTER
    Subject area: Integrated circuits
    2023 Volume 20 Issue 4 Pages 20220536
    Published: February 25, 2023
    Released on J-STAGE: February 25, 2023
    Advance online publication: January 17, 2023
    JOURNAL FREE ACCESS

    This letter presents a relaxation digital-to-analog converter (ReDAC) configuration with positive and negative polarity output with high pass filter (HPF). Its digital input is provided in two’s complement format, to which the proposed ReDAC configuration directly matches. The configuration and principle are shown and the operation has been verified with SPICE simulation. The proposed ReDAC with HPF is an extension of the conventional ReDAC using low-pass filter (LPF) which generates an analog output with only positive polarity.

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  • Tsair-Rong Chen, Bing-Yuan Lai, Yu-Lin Juan, Fu-Hsiang Ho, Yung-Lin Hs ...
    Article type: LETTER
    Subject area: Power devices and circuits
    2023 Volume 20 Issue 4 Pages 20220545
    Published: February 25, 2023
    Released on J-STAGE: February 25, 2023
    Advance online publication: January 05, 2023
    JOURNAL FREE ACCESS

    In this study, a wireless battery charger based on a two-phase parallel inductive power transfer (IPT) topology is developed. The charging power is shared by the two-phase parallel IPT circuits to improve efficiency. The power transferring distance can also be increased by adding the coils of the second phase. A hybrid resonant compensation of LCC-LCC/LCC-S is adopted to provide stable current or voltage output for charging the battery pack. The wireless closed-loop controller is implemented via RF communication. The coils of two-phase IPT circuits share the same magnetic field space to avoid increasing system volume. Decoupling capacitors are added to the RXs to eliminate the cross-coupling effect. The proposed two-phase parallel IPT-based wireless battery charger and a single-phase IPT-based charger are both constructed. The rated output voltage and current are 86.4V and 6A for charging a common 72V/36Ah battery pack. Compared with the single-phase topology, the topology of a two-phase parallel can extend the air gap distance for providing the same output power. The efficiency is also increased by about 3% in CC mode and 2% in CV mode.

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