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Proposal of Potted Inductor with Enhanced Thermal Transfer for High Power Boost Converter in HEVs
유봉기,고정민,김준현,이병국 대한전기학회 2015 Journal of Electrical Engineering & Technology Vol.10 No.3
A hybrid electric vehicle (HEV) powertrain has more than one energy source including a high-voltage electric battery .However, for a high voltage electric battery, the average current is relatively low for a given power level. Introduced to increase the voltage of a HEV battery, a compact, high-efficiency boost converter, sometimes called a step-up converter, is a dc-dc converter with an output voltage greater than its input voltage. The inductor occupies more than 30% of the total converter volume making it difficult to get high power density. The inductor should have the characteristics of good thermal stability, low weight, low losses and low EMI. In this paper, Mega Flux® was selected as the core material among potential core candidates. Different structured inductors with Mega Flux® were fabricated to compare the performance between the conventional air cooled and proposed potting structure. The proposed inductor has reduced the weight by 75% from 8.8kg to 2.18kg and the power density was increased from 15.6W/cc to 56.4W/cc compared with conventional inductor. To optimize the performance of proposed inductor, the potting materials with various thermal conductivities were investigated. Silicone with alumina was chosen as potting materials due to the high thermo-stable properties. The proposed inductors used potting material with thermal conductivities of 0.7W/m·K, 1.0W/m·K and 1.6W/m·K to analyze the thermal performance. Simulations of the proposed inductor were fulfilled in terms of magnetic flux saturation, leakage flux and temperature rise. The temperature rise and power efficiency were measured with the 40kW boost converter. Experimental results show that the proposed inductor reached the temperature saturation of 107°C in 20 minutes. On the other hand, the temperature of conventional inductor rose by 138°C without saturation. And the effect of thermal conductivity was verified as the highest thermal conductivity of potting materials leads to the lowest temperature saturations.
Inductor Design Method of DCM Interleaved PFC Circuit for 6.6-kW On-board Charger
유봉기,이병국,김동희 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.6
Because the on-board charger (OBC) is installed in electric vehicles (EVs), high power density is regarded as a key technology. Among components of the OBC, inductors occupy more than 30% of the total volume. Thus, it is important to reduce the volume and the weight of inductors while maintaining thermal stability. Discontinuous conduction mode (DCM) can satisfy these requirements; however, only a few studies have adopted the DCM operation for OBCs because of the large inductor current ripple. In this paper, a design process is proposed for application of the DCM operation to OBCs. In order to analyze the inductor losses accurately, a numerical formula for the inductor current ripple is deduced based on a detailed analysis. Two inductors are fabricated using several ferrite cores and powder cores taking into consideration the inductor size, inductor losses, and temperature rise. In order to verify the analysis and design process, experimental results are presented that show that the designed inductors satisfy the requirements of the OBCs.
Magnetite 强磁性流體를 이용한 海上流布油類의 除去
金泰玉,柳奉奇 부산대학교 환경문제 연구소 1986 環境硏究報 Vol.4 No.-
In order to remove and recovery the oil spil on the sea-surface, the kerosene-based ferrofluid has been synthesized from the pickling-acid of cold-rolling mill in steel manufacturer with the low cost. By applying magnetic field on the ferrofluid sprayed on the water surface contaminated by the oil, the oil can be removed above 90% and the ferrofluid reused.