• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.53 no.5
• /
• pp.345-352
• /
• 2004

Currently, high data rate PLC(Power Line Communications), up to 100 Mbps, which use frequency bandwidth between 2 MHz and 30 MHz is investigated very hard, and commercial PLC modem for low voltage powerline network (indoor) is coming soon into communication market. For the purpose of developing a fit communication system which has little distortion of signal and attenuation, it is surely necessary to know about channel environments of powerline. Especially, the impedance measurement of the powerline and impedance matching are very important. As is known, since medium-voltage powerline (22.9 ㎸) is still working, it is not so simple to measure the powerline impedance. In our study, a portable impedance measurement equipment is developed. It consists of coupling capacitor, a drain coil and impedance matching transformer. The equipment is easily connected to medium voltage line and impedance of power line is measured using a network analyzer. Also, measurement results are used for impedance matching of PLC signal. In fact, matching transformer with several different impedances are used. The matching transformer is connected between coupling capacitor and signal port. In this paper, the developed portable impedance measurement equipment and impedance measurement results are presented. Also impedance matching technique using matching transformers will be explained. We showed the result of the improved performance by the impedance matching.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.23 no.10
• /
• pp.29-35
• /
• 2009

This paper handles, implementation of multiple access bidirectional serial communications protocol using DC power lines. The normal voltage of the power communication line maintains 24[V] corresponding to level 1 and the host drops the voltage to 12[V] on sending level 0 signal, also the clients normally keeps the line voltage to 24[V] use pull-down circuit to drop the voltage to 12[V] on sending level 1 signal. Host senses the voltage level of the power communication lines and the hosts switches power source from 24[V] to 12[V]. Experimental circuit is designed with one hosts and four clients and verified the power line voltage switching operation depending on the data signal levels on the power line.

• Journal of Electrical Engineering and Technology
• /
• v.12 no.5
• /
• pp.2001-2006
• /
• 2017

This paper explains the effects of the weak signal of a rotating-type electric field mill sensor fabricated for measuring the intensity of the electric field generated by high-voltage direct current (HVDC) power transmission lines. The fabricated field mill consists of two isolated electrode vanes, a motor driver, and a ground part. The sensor plate is exposed to and shielded from the electric field by means of a rotary shutter consisting of a motor-driven mechanically complementary rotor/stator pair. When the uncharged sensor plate is exposed to an electric field, it becomes charged. The rotating electrode consists of several conductive vanes and is connected to the ground part, so that it is shielded. Determining the appropriate design variables such as the speed of the vane, its shape, and the distance between the two electrodes, is essential for ensuring optimal performance. By varying the speed, the weak signal characteristics which is used to signal processing and calibration experiment are quite different. Each weak signal pattern was analyzed along with the output voltage characteristics, in order to be able to determine the intensity of the electric field generated by HVDC power transmission lines with accuracy.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.39 no.8
• /
• pp.24-33
• /
• 2002

For mixed signal circuits that integrate both analog and digital blocks onto the same chip, testing the mixed circuits has become the bottleneck. Since most of mixed signal circuits are functionally tested, mixed signal testing needs expensive automatic test equipments for test input generation and response acquisition. In this paper, a new efficient BIST is developed which can be used for mixed signal circuits. In the new BIST, only faults on embedded resistances, capacitances and its combinations are considered. To guarantee the quality of chips, the new BIST performs both voltage testing and phase testing. Using these two testing modes, all the faults are detected. In order to support this technique, the voltage detector and the phase detector are developed. Experimental results prove the efficiency of the new BIST.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.27 no.6
• /
• pp.541-549
• /
• 2007

This work describes an investigation into the feasibility of using an acoustic emission (AE) technique to evaluate the integrity of a composite actuator with a PZT ceramic under electromechanical cyclic loading. AE characteristics have been analyzed in terms of the behavior of the AE count rate and signal waveform in association with the performance degradation of the composite actuator during the cyclic tests. The results showed that the fatigue cracking of the composite actuator with a PZT ceramic occurred only in the PZT ceramic layer, and that the performance degradation caused by the fatigue damage varied immensely depending on the existence of a protecting composite bottom layer. We confirmed the correlations between the fatigue damage mechanisms and AE signal types for the actuators that exhibited multiple modes of fatigue damage; transgranular micro damage, intergranular fatigue cracking, and breakdown by a short circuiting were related to a burst type signal showing a shortly rising and slowly decaying waveform with a comparably low voltage, a continuous type signal showing a gradual rising and slowly decaying waveform with a very high voltage and a burst and continuous type signal with a high voltage, respectively. Results from the present work showed that the evolution of fatigue damage in the composite actuator with a PZT ceramic can be nondestructively identified via in situ AE monitoring and microscopic observations.

• Journal of Power Electronics
• /
• v.10 no.3
• /
• pp.285-292
• /
• 2010

This paper presents a current mode integrated control technique (CM-ICT) using a modified voltage space vector modulation (MSVM) for Z-source inverter (ZSI) fed induction motor drives. MSVM provides a better DC voltage boost in the dc-link, a wide range of AC output voltage controllability and a better line harmonic profile. In a voltage mode ICT (VM-ICT), the outer voltage feedback loop alone is designed and it enforces the desired line voltage to the motor drive. An integrated control technique (ICT), with an inner current feedback loop is proposed in this paper for the purpose of line current limiting and soft operation of the drive. The current command generated by the PI controller and limiter in the outer voltage feedback loop, is compared with the actual line current, and the error is processed through the PI controller and a limiter. This limiter ensures that, the voltage control signal to the Z-source inverter is constrained to a safe level. The rise and fall of the control signal voltage are made to be gradual, so as to protect the induction motor drive and the Z-source inverter from transients. The single stage controller arrangement of the proposed CM-ICT offers easier compensation. Analysis, Matlab/Simulink simulations, and experimental results have been presented to validate the proposed technique.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.23 no.5
• /
• pp.516-522
• /
• 2020

In this paper, the frequency detector which detects the clock frequency of the embedded system is proposed and analyzed. The proposed frequency detector is consisted of filter and peak voltage detector. The clock signal is converted from square wave to triangular wave by the filter. The peak voltage of the triangular wave is determined according to the frequency response of filter. The peak voltage detector detects and holds the peak voltage of the signal. Moreover, the proposed clock frequency detector can detect the frequency within 1ms and it gives guarantee of real-time operation.

• Journal of Power Electronics
• /
• v.16 no.4
• /
• pp.1298-1305
• /
• 2016

This paper presents the development of a short-circuit protection mechanism on a high voltage switch (HVS) board which is built by a series connection of semiconductor switches. The HVS board is able to quickly detect and limit the peak fault current before the signal board triggers off a gate signal. Voltage clamping techniques are used to safely turn off the short-circuit current and to prevent overvoltage of the series-connected switches. The selection method of the main devices and the development of the HVS board are described in detail. Experimental results have demonstrated that the HVS board is capable of withstanding a short-circuit current at a rated voltage of 10kV without a di/dt slowing down inductor. The corresponding short-circuit current is restricted to 125 A within 100 ns and can safely turn off within 120 ns.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.51 no.7
• /
• pp.317-322
• /
• 2002

This paper presents a linear temperature/voltage relation over a temperature range(0~100$^{\circ}C$) with high-resolution, reasonably god response linearity, reliability, and overall improved performance. A notable feature of the proposed method is that the whole temperature span is divided by 16 subbands thus the variation span of measured voltage is narrowed. Therefore noise characteristic has been improved. The output voltage is amplified after the uniformed DC voltage component is eliminated by offset. We proposed circuit using median value and mean value of digital signal in order to reduce the noise effect. The proposed circuit offers linear temperature/voltage conversion over a wide dynamic range using DSP(TMS320C31) and steinhart equation.

• Proceedings of the KIEE Conference
• /
• 1999.07f
• /
• pp.2721-2723
• /
• 1999

DC and small-signal ac characteristics are examined for a pulse-width modulated (PWM) dc-dc buck-boost converter with a peak voltage modulation (PVM) feedforward control. Circuit model is used to derive an expression for the output voltage in terms of the input voltage and load resistance. Small-signal circuit model is used to derive the input-to-output voltage transfer function (audiosusceptibility).