https://doi.org/10.5207/JIEIE.2026.40.4.241

So Yeon Park ; Yoon Seok Jang

In this paper, we theoretically and experimentally demonstrate the continuous wavelength tuning of flat-top comb spectra in a polarization-diversity loop fiber multiwavelength filter based on variable waveplates (VWs). The multiwavelength filter consists of a four-port polarization beam splitter (PBS), two high birefringence fiber (HBF) segments of the same length, a half-wave plate (HWP), and two VWs, with each VW placed in front of an HBF segment. In the polarization-diversity loop formed by the PBS, the HWP is used to set the effective orientation angle of the second HBF segment to 22.5° with respect to the horizontal axis of the PBS to maximize the visibility of the filter output spectrum. The transfer matrix of the filter was theoretically derived using the Jones matrix formulation, and its transmittance function was obtained from the derived transfer matrix. Based on the filter transmittance, we determined the combinations of the orientation angle (OA) and phase delay (PD) of the VW, which can provide an additional phase difference ranging from 0° to 360° with a 1° increment. Some selected combinations of OAs and PDs were used to calculate flat-top comb spectra, which could be wavelength-tuned in 0.1nm increments. The theoretical analysis was experimentally validated using the fabricated multiwavelength filter. The theoretical and experimental results show that precise wavelength tuning of flat-top comb spectra in this multiwavelength filter can be achieved through simple adjustment of the OAs and PDs of the VWs.

https://doi.org/10.5207/JIEIE.2026.40.4.247

Woong-Jo Jang ; Byung-Chul Yu

This study proposes an AI-based air-dome smart salt farm system to overcome the climate dependencies, contamination risks, and labor-intensive nature of conventional solar salt production. Utilizing a translucent air-dome integrated with geothermal HVAC, the system regulates temperature, humidity, and airflow for year-round operation. Real-time sensor data are processed via cloud-based AI to control the full production cycle?from seawater purification to automated harvesting and packaging. A three-year field demonstration showed a 28% increase in salinity rate, 35% shorter drying time, 22% better quality uniformity, and over 30% energy savings.

https://doi.org/10.5207/JIEIE.2026.40.4.255

Dong-Hyeok Son ; Myoung-Su Kim ; Won-Young Jo ; Sung-An Kim ; Yun-Hyun Cho

This study proposes a novel adaptive sliding mode observer capable of starting without I/F operation and robust against torque disturbance during low-speed operation. If the observer can be applied from the initial startup of the motor, I/F operation becomes unnecessary. This approach addresses key issues associated with conventional methods that switch from I/F operation to sensorless control, such as mitigating transition-induced disturbances and improving response to startup loads. Furthermore, since sensorless operation is possible even in the conventional I/F control region, the overall operating range is extended compared to existing method. To validate the proposed observer, a design method is presented, and its stability is determined using Lyapunov stability theory. The existing observer and the proposed observer are compared through simulation, and the proposed observer is verified through experiments.

https://doi.org/10.5207/JIEIE.2026.40.4.264

Jin-Yong Bae

In this paper, the resonance and switching characteristics of a wireless power transfer system employing a planar ferrite sheet are analyzed. The proposed wireless power transfer system seeks to establish an optimal design methodology for wireless power transmission based on a full-bridge converter employing four switching devices. To this end, the switching characteristics were analyzed through theoretical operating waveforms and mode analysis. Based on the equivalent circuit of the resonant compensation network, the zero-voltage switching (ZVS) and zero-current switching (ZCS) operating regions, along with the voltage gain characteristics as functions of magnetizing inductance and load conditions, were evaluated using MATLAB. Furthermore, by comparing the PSIM simulation results with the experimental results, the effectiveness of the proposed system was validated, and an optimal design procedure for a 200-W wireless power transfer system is presented and discussed.

https://doi.org/10.5207/JIEIE.2026.40.4.276

Seung-Joon Lee ; Kyo-Beom Lee

This paper proposes an autonomous robotic deburring method for the deburring process of die-casting parts using vision-based burr detection information. A 3D laser scanner is used to acquire point cloud data of a die-cast workpiece, and 2D shape information is generated through image processing. The generated shape information is compared with CAD design data to identify burr regions and distributions. A speed-controlled robotic deburring path is automatically generated based on the detected burr information and a lookup table-based speed control scheme is applied. The effectiveness of the proposed method is validated through experiments using a robotic deburring system.

https://doi.org/10.5207/JIEIE.2026.40.4.285

Jae-Sub Lee ; Rae-Young Kim

Arc flash is among the most hazardous electrical accidents in industrial power systems, instantaneously generating high-temperature plasma that causes severe worker injury and equipment damage. While NFPA 70E and IEEE 1584-2018 provide systematic risk assessment procedures, the Korean Electro-technical Code (KEC) has yet to establish criteria for incident energy (IE), arc flash boundary, and PPE requirements. This study analyzes arc flash causes based on NFPA 70E and IEEE 1584-2018, examining key parameters including short-circuit current, protective device clearing time, and working distance. The IEEE 1584-2018 model was applied together with the instantaneous trip time range specified in KS C IEC 60947-2 to compare incident energy under standard and high speed clearing conditions. Results show that reducing clearing time significantly decreases incident energy, bringing it below the second-degree burn threshold. Simulation verification confirmed that shorter clearing times lower the PPE category and substantially narrow the arc flash boundary. These findings demonstrate that optimizing protective device clearing time, even within the existing KEC framework, offers the most practical and effective approach to reducing incident energy, providing meaningful foundational data for future domestic risk assessment standards.

https://doi.org/10.5207/JIEIE.2026.40.4.293

Pyeong-Kang Kim ; Ui-Chang Mun ; Seung-Ho Song

This paper proposes a high-efficiency control and design method for a flyback converter-based unfolding inverter for residential photovoltaic power generation systems. Residential photovoltaic power generation systems require miniaturization and high-efficiency operation of inverters due to limited installation space and frequent low-power operation conditions. Under low-power conditions, switching losses and the reactive power effect of the filter capacitor cause degradation in efficiency and power factor. To address these problem, this paper proposes a method that considers low-voltage input and low-power operating conditions. For high-efficiency operation, a two-phase interleaved structure and BCM operation are applied to reduce input current and peak current stress. In the low-current region, the operating mode is changed to DCM to limit the switching frequency. The grid-side filter was designed based on a 50 W operating point to ensure the target power factor. When the PV output power is low, burst-mode operation is applied to operate the inverter intermittently. To verify the proposed method, a 500-W flyback-converter-based unfolding inverter was modeled in PSIM. The simulation results show that the maximum switching frequency was reduced from 1.6 MHz to 60 kHz, and switching loss was reduced by 80%. In addition, a power factor of 0.99 was achieved by applying the burst mode operation. These results verify the validity of the proposed control method.

https://doi.org/10.5207/JIEIE.2026.40.4.301

Young-Hye Choi

This study evaluates the economic feasibility of integrating an energy storage system (ESS) with a self-consumption photovoltaic (PV) system for a vocational training institution operating under an industrial electricity tariff. A 39.6 kWp PV system was modeled using PVsyst, yielding an annual electricity generation of 51,288 kWh, a specific yield of 1,295 kWh/kWp·yr, and a performance ratio (PR) of 88.32%. Based on the results of a previous PV study and the facility’s daytime load characteristics, the baseline self-consumption ratio was set to 80%. Four ESS capacity scenarios (20, 40, 60, and 80 kWh) were analyzed using an incremental cash-flow approach. The annual net benefits of the ESS scenarios were estimated at KRW 338,524, KRW 523,184, KRW 553,980, and KRW 430,912, respectively. The corresponding payback periods were 29.5, 38.2, 54.2, and 92.8 years, while all net present values (NPVs) were negative at a 6% discount rate, indicating that none of the scenarios achieved economic feasibility under the assumed conditions. As a case study of a vocational training institution, the results indicate that ESS integration improved the self-consumption ratio but did not provide sufficient economic benefits to justify the investment. If ESS installation is required for policy or operational purposes, the 20?40 kWh range may be considered a preliminary capacity range for further evaluation. However, this should not be interpreted as an economically optimal or generally applicable ESS capacity.