Radiation noise due to EMI noise generated by the driving circuits of LED lighting devices in a medical imaging room was reduced by decreasing the noise source in the driving circuits and changing the number of corrections in EMI filters. Noise attenuation and filter changes enabled driving circuits that reduced the electromagnetic waves. Such circuits were efficiently designed by using capacitors and inverters in a given space. Therefore, the malfunction of radiation devices can be minimized by using EMI-reduction filter circuits, and reliable operation of medical devices can be expected by blocking electromagnetic waves.

In this paper, the changes in the electrical characteristics (arc energy, contact resistance, and bouncing phenomenon) due to the deterioration of the contact are analyzed. The results are generally consistent and can be analyzed for contact deterioration. The results of the experiment demonstrate that the arc energy is linearly related to the current when the contact samples and the voltage conditions are the same. The contact resistance varies due to multiple factors, but is generally within a certain range, and the contact deterioration can be determined. Contact stabilization can be detected by the decrease in the bouncing phenomenon due to deterioration (the change of the shape of the contact).

This study analyzed the Vulnerability of Network Communication devices when IEMI is coupled with the Network System. An Ultra Wide Band Generator (180 kV, 700 MHz) was used as the IEMI source. The EUTs are the Switch Hub and Workstation, which are used to configure the network system. The network system was monitored through the LAN system configuration, to confirm a malfunction of the network device. The results of the experiment indicate that a malfunction of the network occurs as the electric field increases. The data loss rate increases proportionally with increasing radiating time. In the case of the Switch Hub, the threshold electric field value was 10 kV/m for all conditions used in this experiment. The threshold point causing malfunction was influenced only by the electric field value. The correlation between the threshold point and pulse repetition rate was not found. However, in case of the Workstation, it was found that as the pulse repetition rate increases, the equipment responds weakly and the threshold value decreases. To verify the electrical coupling of the EUT by IEMI, current sensors were used to measure the PCB line inside the EUT and network line coupling current. As a result of the measurement, it can be inferred that when the coupling current due to IEMI exceeds the threshold value, it flows through the internal equipment line, causing a malfunction and subsequent failure. The results of this study can be applied to basic data for equipment protection, and effect analysis of intentional electromagnetic interference.

This study analyzed the change of electrical characteristics of a photocoupler when a narrow-band electromagnetic wave was combined with the photocoupler. A magnetron (3 kW, 2.45 GHz) was used as the narrow-band electromagnetic source. The EUT was Photocoupler (6N139) and the input signal was divided into two types: a square pulse and the second signal is 0 V. The malfunction of the photocoupler was confirmed by monitoring the variation in the output voltage of the photocoupler. As a result of the experiment, changes in the malfunctioning was observed as the electric field was increased. There are three types of malfunction modes: delay, output voltage off, and fluctuation. Bit errors were analyzed to verify the electrical characteristics of the photocoupler by narrow-band electromagnetic waves. The result of this study can be used as basic data for the effect analysis of photocoupler protection and impact analysis of high-power electromagnetic waves.

Electrical energy is playing an increasingly vital role as the primary energy source in everyday life. With the increase in electric power consumption, power facilities are under an increasing stress and must operate at a high capacity. Consequently, the demand for electric power cables in power transmission and distribution lines is rapidly increasing. Underground distribution lines have been steadily replacing the aboveground lines owing to the increase in electric power demand and the need to increase the supply voltage. In addition to line damage, worker safety is of primary concern in this type of underground infrastructure.In this study, to improve the safety of workers dealing with underground transmission lines, we analyzed the electromagnetic field generated around the distribution line and determined the basic criteria for developing a device that can detect a live underground line.

The changes in the electrical characteristics of CMOS ICs due to coupling with a narrow-band electromagnetic wave were analyzed in this study. A magnetron (3 kW, 2.45 GHz) was used as the narrow-band electromagnetic source. The DUT was a CMOS logic IC and the gate output was in the ON state. The malfunction of the ICs was confirmed by monitoring the variation of the gate output voltage. It was observed that malfunction (self-reset) and destruction of the ICs occurred as the electric field increased. To confirm the variation of electrical characteristics of the ICs due to the narrow-band electromagnetic wave, the pin-to-pin resistances (Vcc-GND, Vcc-Input1, Input1-GND) and input capacitance of the ICs were measured. The pin-to-pin resistances and input capacitance of the ICs before exposure to the narrow-band electromagnetic waves were 8.57 MΩ (Vcc-GND), 14.14 MΩ (Vcc-Input1), 18.24 MΩ (Input1-GND), and 5 pF (input capacitance). The ICs exposed to narrow-band electromagnetic waves showed mostly similar values, but some error values were observed, such as 2.5 Ω, 50 MΩ, or 71 pF. This is attributed to the breakdown of the pn junction when latch-up in CMOS occurred. In order to confirm surface damage of the ICs, the epoxy molding compound was removed and then studied with an optical microscope. In general, there was severe deterioration in the PCB trace. It is considered that the current density of the trace increased due to the electromagnetic wave, resulting in the deterioration of the trace. The results of this study can be applied as basic data for the analysis of the effect of narrow-band high-power electromagnetic waves on ICs.

The power relay can easily control high voltage and high current through metallic contacts. In addition, it has the advantage in reasonable price. So it has been used in many applications. But the power relay has a weak point by mechanical movements. These mechanical movements cause the bouncing phenomenon. Arc and bouncing phenomenon are the main causes of electric abrasion and material erosion. In this study, mechanical repetitive experiments and repetitive experiments in electrically connected state are conducted. Then these two experimental results in terms of bouncing phenomenon and changes in the contact surface are compared. In all number of repetitions, contacts in an electrically connected state cause smaller number of bounce. Also, It has lower contents of silver on eroded surface than the other. The experimental results would be helpful to the further study of contacts life span.

Citations

• Machine Tool Touch-Probe Electrical Contact Material Optimization Experimental Study
  Min Lyul Lee, Seungwook Kim, Daeyong Jeong, Sun Kon Lee
  Journal of the Korean Society of Manufacturing Process Engineers.2023; 22(6): 24.     CrossRef

This study examined the malfunction mode of the HCMOS IC under narrow-band high-power electromagnetic wave. Magnetron is used to a narrow-band electromagnetic source. MFR (malfunction failure rate) was measured to investigate the HCMOS IC. In addition, we measured the resistance between specific pins of ICs, which are exposed and not exposed to the electromagnetic wave, respectively. As a test result of measurement, malfunction mode is shown in three steps. Flicker mode causing a flicker in LED connected to output pin of IC is dominant in more than 7.96 kV/m electric field. Self-reset mode causing a voltage drop to the input and output of IC during electromagnetic wave radiation is dominant in more than 9.1 kV/m electric field. Power-reset mode making a IC remained malfunction after electromagnetic radiation is dominant in more than 20.89 kV/m. As a measurement result of pin-to-pin resistance of IC, the differences between IC exposed to electromagnetic wave and normal IC were minor. However, the five in two hundred IC show a relatively low resistance. This is considered to be the result of the breakdown of pn junction when latch-up in CMOS occurred. Based on the results, the susceptibility of HCMOS IC can be applied to a basic database to IC protection and impact analysis of narrow-band high-power electromagnetic waves.

In this paper, we designed and fabricated electromagnetic induction based scaffold type energy harvester. For energy harvesting, mechanical energy of vertical motion is transferred to rotational energy using rack gear and multiplying gear was used to maximize energy transfer. To optimize design parameters, physical structure of energy harvester was modeled using finite element method. The effect of multiplying gear ratio and frequency levels of applied mechanical energy on energy generation efficiency are analyzed by computer simulation and experimental test. Experimental results showed that maximum 25.36 W of electric power can be achieved at the frequency of 2 Hz and 1:77 of gear ratio with only 5 mm of vertical changes on scaffold structure.

In this paper, we studied the magnetic composite sheets for electromagnetic wave noise absorber of quasi-microwave band by using soft magnetic FeSiCr and Fe50Ni flakes with the thickness of about 1 μm and polymer. The magnetic hysteresis curve including saturation magnetization and residual magnetization and the complex permeability characteristics of the composite sheets were investigated to clarify the mixing effect on electromagnetic wave absorption properties. The saturation magnetization was decreased about 10% while the residual magnetization was increased about 15% and the real parts of complex permeability at below 500 MHz were increased 0.6～4 while those values at above 500 MHz were decreased 0.4～2.5 according to the change of contents of FeSiCr and Fe50Nipowders. As a result, the reflection loss can be moved to the lower frequency from 2∼3 GHz to 1∼1.5GHz as the contents of Fe50Ni flaky powder into FeSiCr flaky powder was increased up to 50%.

Recently, energy harvesting technologies are considered as the great alternatives to reduce the dependency on secondary batteries. In this paper, we proposed PCB type energy harvester which can be directly integrated with other electronic components on same board. To form the three dimensional coil structure, two PCBs with patterned metal lines are solder bonded. For magnetic induction, inside of coil structure was filled with magnetic substance and rotary motioned external magnets are applied to near the harvester. The effects of metal wire width on PCB, thickness of magnetic substance, and frequency of rotary motion on energy harvesting performance are analyzed by computer simulation and experiments. Experimental results showed 29.89 ㎼ of power generation performance at the frequency of 5.2 Hz and it is shown that designed harvester can be effectively applied on vibration environment with very limited frequency.

This paper dealt with the radiated electromagnetic wave detection of partial discharge (PD) in oil for insulation diagnostics of oil-immersed transformers. Three types of electrode system were fabricated to simulate the insulation defects that could occur in oil-immersed transformers. Frequency components of radiated electromagnetic wave in oil was measured by broadband bi-conical antennas of 300 MHz∼2 GHz and a spectrum analyzer of 9 kHz∼3 GHz. Frequency component of electromagnetic waves from PD in oil were highly distributed at 500 MHz. From the result, a narrow-band monopole antenna with the center frequency of 500 MHz was fabricated. We could detect PD signal in insulation oil without an influence of external noise by a measurement system which consists of the prototype monopole antenna, a LNA (Low Noise Amplifier), an oscilloscope and a spectrum analyzer.

The rated voltage has been rising in order to minimize the losses in power transmission. The high voltage electric machines should be minimized due to the constraints of space. Therefore, the temperature of high voltage electric apparatuses easily exceeds the temperature limits. In this paper, it is investigated that how to minimize the internal temperature rising of a high voltage switchgear by adjusting the arrangement of bus bars. High voltage switchgears consist of a circuit breaker, a CT, a PT, a earthing switches, bus bars, and so on. It is very difficult to estimate the electromagnetic properties of a high voltage switchgear due to these various environments and structures. In this paper, analyses are focused on the electromagnetic characteristics of bus bars according to the arrangement method and the enclosures to simplify the electromagnetic characteristics of a switchgear. It is found that the characteristics of electric field intensity and electromagnetic losses in bus bars are influenced by the arrangement method of bus bars. However, it is confirmed that the electromagnetic characteristics of enclosures are not affected by the arrangement of bus bars. In this paper, the arrangement methods of bus bars to minimize the electric field intensity and electromagnetic losses are suggested. It is expected that the research results are helpful to design and develop an electrically reliable high voltage switchgear.

This paper dealt with the measurement and analysis of electromagnetic waves radiated from a partial discharge (PD) source in insulation oil to apply condition monitoring of oil-immersed transformers. Two types of narrow-band monopole antennas with the resonant frequency of a 500 MHz and a 1 GHz were designed and fabricated. Also, a needle plane electrode system was manufactured to simulate PDs and the curvature radius of the needle is 10 pm and the diameter of the plane is 60 mm. Electromagnetic wave was measured by the PD measurement system with the monopole antennas. Detection sensitivity of the fabricated antenna was compared for the same P1) magnitude; 620 mVpeak for the 500 MHz antenna and 960 mV1,t for the 1 GHz antenna to the PD magnitude of 74 pC. Consequently, the 1 GHz monopole antenna is more effective to detect PDs in oil immersed transformers.

Frequency domain measurement of propagation loss for ultra high frequency (UHF) partial discharge in the winding of power transformer using a spectrum analyzer and pulse generator is presented. We compared the performance of the method using a network analyzer with and without a winding. Using a network analyzer simplifies the measurement and offers better dynamic range and frequency range. It also provides precise propagation loss within the winding in frequency domain at UHF range. We applied this method to measure UHF propagation loss of transformer mock-up, modeled 154 kV 20 MVA power in KEPCO substation.

This paper describes the characteristics of electromagnetic wave propagation wave propagation in power transformer. A transformer which is similar which is similar to 154 kV single phase on-site transformer unit was provided for the purpose of the experiment. The 12dieletric windows on the transformer enclosure to install UHF(ultra high frequency) sensors and the full scale mock ups of winding and the core were also euipped in the transformer. Every sensors to be installed to the transformer was tested and verified whether they show same characteristics or not beforethe experiment. A discharge gap which was used as a PD (partial discharge) source moved to or not before the experiment. A discharge gap which was used as a PD (partial discharge) source moved to several necessary locations in the transformer to simulate dielectrie defects. Propagation times of electromagnetic wave signal from PD source to sensors decided by the routes of both reflection phenomenon and diffraction phenomenon were compared each other. The experimental results showed propagation route of the PD signal makes an effect on the frequency spectrum of front part of the signal and the magnitude of the signal and propagation time of the signal when the signal is captured on the sensor

Citations

• A Study on the Operation Characteristics of Arc Fault Detection Device under Arc Generation
  Heejun Kwon, SungHwan Kim, Jihee Lee, Kiseok Kim, Haiyoung Jung
  International Journal of Fire Science and Engineering.2024; 38(2): 27.     CrossRef
• Highly Sensitive Partial Discharge Sensor with Remote Monitoring Capabilities
  Kyoo-Nam Choi
  The Journal of the Korea institute of electronic communication sciences.2015; 10(3): 349.     CrossRef

Citations

• Harmonics Analysis of Leakage Current due to Artificial Contamination of Distribution Arresters
  Jae-Jun Park
  The Transactions of The Korean Institute of Electrical Engineers.2012; 61(9): 1306.     CrossRef
• Analysis of Leakage Current Waveforms for Transmission Line Porcelain Insulators due to ESDD Contamination
  Jae-Jun Park
  The Transactions of The Korean Institute of Electrical Engineers.2012; 61(10): 1461.     CrossRef