• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.8
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• pp.1163-1168
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• 2013

The maximum allowable value of loop impedance($Z_s$) to secure the operation of overcurrent protective devices and the safety for indirect contact is a very important in TN-C-S system. The loop impedance is divided into inner loop impedance which consumer can adjust and external loop impedance($Z_e$) which only electric operator can adjust. Thus, an external loop impedance which limits to less than a certain value is a very important factor for human body protection against electric shock in TN-C-S system. The concept of loop impedance($Z_s$) is recently introduced to the domestic, the study about external loop impedance is yet insufficient. However, the study about the reference impedance as specified by the IEC 60725 standard to improve the quality and reliability of the power supply is being made. In this paper, reference value of external loop impedance($Z_e$) to meet domestic environment will be proposed by the nationwide measurement and statistical analysis.

• Journal of Ceramic Processing Research
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• v.13 no.spc2
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• pp.163-165
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• 2012

Impedance spectroscopy informs electrical properties of materials as accumulated charges, contact status between electrode and organic materials. We carried out impedance spectroscopy of organic light-emitting diodes as ITO/Alq3(60 nm)/Al on temperatures from 10 K to 300 K. The result described Z'-Z" plot, cole-cole plot and dielectric relaxation time τ. Z'-Z" plot means that real and imaginary part of materials in organic and electrode by frequencies and temperature. Z' as real part of impedance by applied frequency depending on temperature shows the plateau in low frequency region as Rs+ Rp and over 100 kHz in high frequency region as Rs. Cole-cole plot shows resistance of materials in equivalent circuit of the device by temperatures. And equivalent circuit and dielectric relaxation could be accomplished by using the complex impedance analysis.

• Journal of Electrochemical Science and Technology
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• v.12 no.4
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• pp.415-423
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• 2021

For a battery module where single cells are connected in series, the single cells should each have a similar state of charge (SOC) to prevent them from being exposed to an overcharge or over-discharge during charge-discharge cycling. To detect the existence of unbalanced SOC cells in a battery module, we propose a simple measurement method using a single-frequency response of electrochemical impedance spectroscopy (EIS). For a commercially available graphite/nickel-cobalt-aluminum-oxide lithium-ion cell, the cell impedance increases significantly below SOC20%, while the impedance in the medium SOC region (SOC20%-SOC80%) remains low with only minor changes. This impedance behavior is mostly due to the elementary processes of cathode reactions in the cell. Among the impedance values (Z, Z', Z"), the imaginary component of Z" regarding cathode reactions changes heavily as a function of SOC, in particular, when the EIS measurement is performed around 0.1 Hz. Thanks to the significant difference in the time constant of cathode reactions between ≤SOC10% and ≥SOC20%, a single-frequency EIS measurement enlarges the difference in impedance between balanced and unbalanced cells in the module and facilitates an ~80% improvement in the detection signal compared to results with conventional EIS measurements.

• Journal of the Korean Magnetics Society
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• v.27 no.4
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• pp.135-139
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• 2017

The magneto-impedance effect (MI effect) has been investigated in metal core/soft magnetic shell composite wires fabricated by electrodeposition of $Ni_{80}Fe_{20}$ on Cu wire (diameter $190{\mu}m$). The diagonal impedances $Z_{zz}$ and $Z_{{\theta}{\theta}}$ in cylindrical coordinate showed strong MI effect for the magnetic field applied along z-axis, while the off-diagonal impedance $Z_{{\theta}z}$ showed very weak MI effect. We have tried to develop the Cu $core/Ni_{80}Fe_{20}$ shell composite wire having strong MI effect in off-diagonal impedance by electrodeposion under torsional strain. The core/shell composite wire electrodeposited under torsional angles above $270^{\circ}$ showed significantly enhanced MI effect in the off-diagonal impedance. The maximum MI effect was observed in the composite wire electrodeposited under torsional angle of $360^{\circ}$. The developed method to enhance off-diagonal MI effect is expected to increase the applicability of the core/shell composite wire to magnetic sensor material.

• Journal of Advanced Navigation Technology
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• v.25 no.5
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• pp.370-376
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• 2021

development of the aerospace industry is increasing the research of projectiles. In addition, many tests are under way and many failures occur accordingly. Projectiles should be able to minimize failures because they are more dangerous than other electronic equipment. Therefore, it is necessary to verify wiring before powering the projectile. Accordingly, the wiring status was verified by resistance measurements. However, the wiring test of the previous resistance measurement method cannot be accurately measured due to devices such as capacitors and inductors in the projectile circuit. In this paper, impedance is measured in the connection state of cables and projectiles using a TDR meter. The Z-Segmentation algorithm is used to set the reference value for the measured steady state impedance. The Z-Segmentation algorithm first finds the peak values of the impedance waveform using a Kalman filter and obtains the final impedance peak segment through segmentation. In this way, the wiring status is determined based on the reference value for the normal state of the wiring.

• Journal of Electrical Engineering and Technology
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• v.12 no.3
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• pp.1203-1210
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• 2017

Switched-inductor (SL) Z-source three-level inverter is a novel high power topology. The SL based impedance network can boost the input dc voltage to a higher value than the single LC impedance network. However, as all the neutral-point-clamped (NPC) inverters, the SL Z-source three-level inverter has to balance the neutral-point (NP) potential too. The principle of the inverter is introduced and then the effects of NP potential unbalance are analyzed. A NP balancing method is proposed. Other than the methods for conventional NPC inverter without Z-source impedance network, the upper and lower shoot-through durations are corrected by the feedforward compensation factors. With the proposed method, the NP potential is balanced and the voltage boosting ability of the Z-source network is not affected obviously. Simulations are conducted to verify the proposed method.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1977-1978
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• 2008

In this paper, we compare performance of common-mode rejection between a differential and a non-differential amplifier system with two electrodes. A differential amplifier system is constant for common-mode rejection ratio(CMRR) on the frequency domain. But a non-differential amplifier's CMRR is determined by $Z_{FB}/Z_e$ ($Z_{FB}$ ; feedback impedance, $Z_e$; electrode impedance). There is trade-off between a non-differential amplifier's CMRR and its differential input impedance. And a non-differential amplifier system has some advantages for a bio-potential measurement with two electrodes because a designer can control the impedance between the body and system's common.

• Journal of Magnetics
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• v.18 no.4
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• pp.428-431
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• 2013

We demonstrate that a partial loading of $Ni_{0.5}Zn_{0.5}Fe_2O_4$ (Ni-Zn ferrite) film remarkably improves impedance matching of electrically small $Ba_3Co_2Fe_{24}O_{41}$ ($Co_2Z$) hexaferrite antenna. A 3 ${\mu}m$ thick Ni-Zn ferrite film was deposited on a silicon wafer by the electrophoresis deposition process and post-annealed at $400^{\circ}C$. The fabricated Ni-Zn ferrite film has saturation magnetization of $268emu/cm^3$ and coercivity of 89 Oe. A partial loading of the Ni-Zn ferrite film on the $Co_2Z$ hexaferrite helical antenna increases antenna return loss to 24.7 dB from 9.0 dB of the $Co_2Z$ antenna. Experimental results show that impedance matching and maximum input power transmission to the antenna without additional matching elements can be realized, while keeping almost the same size as the $Co_2Z$ antenna size.

• Korean Journal of Materials Research
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• v.13 no.10
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• pp.658-662
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• 2003

In this study, we have tried to find the optimized design variables of the matching layer which is important part of thickness mode ultrasonic transducer and finally reach the conclusion that the electrical property of piezo-element must be under consideration when the optimized acoustic impedance is estimated. Proper expression of the effective impedance of front load at free resonant frequency(: $Z_{f}$ $^{(0)}$ /) has been induced by introducing the principle of binomial multilayer transformer and gradient based numerical method is utilized to find the most acceptable value of $Z_{ f}$/$^{(0)}$ . Optimized point of acoustic impedance can be calculated directly from $Z_{f}$ $^{(0)}$ using some simple formula which we propose. We also verify our result by both numerical and experimental method and get a good enhancement especially it concern to the bandwidth of ultrasonic transducer.

• Journal of Biomedical Engineering Research
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• v.9 no.1
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• pp.109-116
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• 1988

In this paper, principles of impedance tenchinque and relationship between stroke volume and impedance change were theoretically explained. An impedance cardiograph was designed and constructed. Its reproducibility was verified by experiment. Until now, the peak point of dZ/dt waveform, first derivative of impedance change(${\Delta}$Z) , has been detected by software technique requiring considerable time to process. However in this paper its peak point was found using hardware for saving processing time. Useful cardiac parameters such as stroke volume and contractility of cardiac muscle were measured noninvasively. The reproducibility of the instrument was measured to be better(less than 10%) than that of clinical standard method such as thermodilution (more than 30%). Hence impedance cardiography was found to be better techique for monitoring stroke volume and myocardial contractility for pre and post operation, and pharmacological studies.