To satisfy increasing demands for ecofriendly vehicles, researchers are now studying electric vehicle (EV)-related technologies. In particular, integrated bidirectional onboard battery charger (OBC)/low-voltage DC-DC converter (LDC) modules are being researched to improve the efficiency of onboard chargers for EV charging applications. In this study, a numerical analysis method is proposed that considers the power loss and heat flow characteristics in the design of a 7.2 kW integrated bidirectional OBC/LDC module. The developed module supports four operating modes depending on the service situation: OBC and LDC single operation, OBC/LDC simultaneous operation, and LDC operation. The mode is selected based on the power system flow. The characteristics of the circuit were analyzed in each of the four modes to compute the heat loss from the major heating elements. The results of a numerical analysis of the internal cooling characteristics showed that the internal temperature was higher in the OBC single operating mode than in the OBC and LDC simultaneous operating mode in which the power loss was the highest. The results emphasize the importance of ensuring that cooling designs consider the characteristics of various modes as well as the worst-case power loss.Researchers currently working in the area of integrated power converters are focusing on a variety of circuit improvements [1][2][3]. For example, onboard chargers (OBCs) and low-voltage DC-DC converters (LDCs) are being researched as a way to overcome space limitations and poor fuel economy of systems with connected batteries [4][5][6][7]. These integration efforts are seeking to leverage high-efficiency circuit structures using miniaturized, lightweight components, such as switch-mode power supplies (SMPSs). Studies are also underway to solve the low reverse recovery charge problem using a GaN element with a totem-pole structure in continuous current mode (CCM) operation [8,9]. Another example is the use of high-frequency switching signals using an insulation-type converter, such as a series-loaded resonant DC-DC converter (SRC) or LLC resonant converter, to minimize power loss in the DC-DC converters commonly used for the auxiliary charging of EVs by applying [10][11][12][13]. In addition, as cooling performance has become an important consideration in circuit improvement, experimental methods of evaluating the cooling performance of heating elements are also being researched [14]. Note that such studies typically employ experimental methods instead of the numerical methods commonly used in battery pack design [15].Recently, the Buck Converter of the two-way charging system has been proposed as an optimization control method considering the State of Charging (SOC) [16][17][18][19][20] and the State of Healthy (SOH) [21][22][23], and the research is being actively conducted. Among the SOC methods, the CC-CV (Constant Current/Constant Voltage) method, which is the simplest basic model and is controlled according to the determined voltage and current [16], and ...

The onboard charger (OBC)/low-voltage DC-DC converter (LDC) integrated power inverter for electric vehicles comprises multiple electrical elements that can heat up, which can cause performance degradation and system instability issues in electric vehicles. To address this, a cooling system is included in the OBC/LDC integrated power inverter, which primarily uses water as a coolant. In this water cooling method, controlling the flow rate of water is critical for uniform cooling of the component. Thus, we propose an optimization method that helps determine the design variables to ensure uniform flow rate in each channel of the water-cooled system. The control variables for fluid-flux flow distribution optimization are selected by performing flow analysis for the initial design shape and analyzing their effects on fluid-flux flow distribution. For optimization analysis, the central composite design technique was applied; in addition, multi-response surface optimization using the same flow rate for each channel was performed. The optimization results were compared and verified using desirability functions based on the flow ratio of the cooling water channel, product function, and error function. Among single-response objective functions, the product function showed excellent performance. However, optimization using a multi-response objective function showed significantly higher prediction accuracy than the single-response function: using the optimized design obtained with the multi-response objective function improved the fluid-flux flow distribution uniformity by approximately 90% or more than the initial design.

In this paper, we develop simplified finite element (FE) models for butt-, lap-and T-welded joints by performing numerical and experimental experiments. Three-point bending tests of butt-and lap-welded specimens are performed to obtain the stiffness of the specimens and the strains at points near the welding beads. Similarly the stiffness and strains of T-welded specimen are measured by applying a point load at the end of the specimen. To develop simplified FE models, we consider the shape parameters of width, thickness and the angle of weld elements in the numerical simulations. The shape parameters of the simplified FE models are determined by building linear regression models for the experimental data sets.

This study analyzed design factors to maximize energy efficiency, via numerical analysis, through an examination of the characteristics of a heating system that uses permanent magnets and is employed for preheating in the aluminum cladding extrusion process. The design parameters of the billet heater using permanent magnets are the magnetic flux direction, the number of magnets, clearance, and eccentricity. The magnetic flux density, current density, power loss, temperature, and energy consumption characteristics were examined using the results of the parameter variations. Numerical analysis for the base model was conducted, and it was experimentally verified that the aluminum billet reached 450 °C in about 260 s, and the temperature error at that time was about 2%. The analysis results show that the optimal factor conditions vary significantly depending on the magnetic force direction of the permanent magnet, that is, the circumferential (tangential) and centrifugal (normal) directions. Furthermore, eccentricity has an effect on efficiency in general, and the narrower the clearance was between the magnet and billet, the higher the efficiency achieved. That is, it was confirmed that the power loss increased by about 1.79% in the four permanent magnets to the tangential model, and increased by about 10.51% in the 12 permanent magnets to the tangential model when an eccentricity of 2 mm was applied at a clearance of 2.5 mm. In addition, the optimal design parameters of a system that heats aluminum billets with a diameter of 60 mm and a length of 70 mm were proposed, and the importance of the design parameters was revealed. In this study, it was found that 12 magnets were the most effective when the magnetic flux pole direction was tangential.