Yeonho Jeong

Experimental investigation of the oil/water/oil liquid-membrane separation of toluene and n-heptane : I. Batch test of a mixer-settler

Abstract The separation of toluene/n-heptane mixtures was investigated through the liquid-membrane permeation method employing a batch mixer-settler. The separation performances, represented by the permeation rate, emulsion stability and separation factor, were analyzed systematically by varying the operation parameters: the contact time, the ratio of the volume of solvent to that of emulsion, the ratio of surfactant solution to that of feed in emulsion, the surfactant concentration and the mixing intensity.

Experimental investigation of the oil/water/oil liquid-membrane separation of toluene and n-heptane : II. Continuous test of a countercurrent permeator

Abstract A countercurrent permeator of the modified Oldshue-Rushton type was designed and used for the continuous liquid-membrane separation of toluene and n-heptane. As in the batch test (Part I of this series) the system parameters were systematically varied to analyze the performance of the permeator. In addition to the parameters for the batch system, hydrodynamic variables (such as emulsion viscosity, specific gravity difference between the emulsion aggregates and the solvent, and flow rates) played important roles. It is recommended that total emulsification should be avoided for a stable operation of the permeator, and optimum ranges of individual operating conditions are proposed.

A high efficiency critical mode boost PFC using a variable inductor

In low-to-mid power applications, a critical conduction mode (CRM) boost power factor corrector (PFC) is widely used due to its simple control and a reduced switching loss. One of the important characteristics of CRM boost PFC is that the switching frequency is not constant and the range of variation is wide. Due to this variability of the switching frequency, there is a design guideline, which must be satisfied. That is, the minimum switching frequency must be higher than the audible frequency. In that reason, a small boost inductance is required to increase the switching frequency. However, this increases the switching loss resulting in a reduced efficiency. In this paper, a new method of improving the efficiency using a variable inductor is proposed. A variable inductor can be implemented by a simple auxiliary circuit. At nominal, where a high efficiency is required, the proposed method operates with a large inductance, which results in the improved efficiency with a decreased switching frequency. On the other hand, when the switching frequency decreases to the audible frequency, the inductance is changed to a smaller value, keeping the frequency higher than the audible frequency over all the range of input line voltage.

LLC resonant converter with high voltage gain using auxiliary LC resonant circuit

To design a LLC resonant converter optimally in the wide input voltage, the LLC resonant converter with a high voltage gain using an auxiliary LC resonant circuit is proposed. The auxiliary LC resonant circuit operates as a variable inductor, and it is represented as an effective magnetizing inductance combined with the magnetizing inductance. In the nominal state, the auxiliary LC circuit provides a high effective magnetizing inductance to minimize the primary circulating current for a high efficiency. During the hold-up time, the auxiliary LC circuit leads the effective magnetizing inductance to be reduced to obtain the high voltage gain. Therefore, an optimal design of the LLC resonant converter, which reduces the primary conduction loss and switching loss, is possible. The proposed converter is verified by experimental results with a 330-390V input 56V/350W output prototype.

An Asymmetric Half-Bridge Resonant Converter Having a Reduced Conduction Loss for DC/DC Power Applications With a Wide Range of Low Input Voltage

A new asymmetric half-bridge (HB) resonant converter for dc/dc power system with a wide range of low input voltage is proposed in this paper. The proposed converter is easily derived based on the switch integration technique, merging a buck–boost, which is the same with the active-clamp forwards primary circuit, and the HB LLC resonant converter. By adopting the buck–boost circuit in front of the HB LLC resonant converter, higher input voltage of LLC resonant converter stage can be achieved. As a result, the primary conduction loss can be significantly reduced. In addition, to cover wide input voltage range, an asymmetric pulse width modulation control is applied. It can mitigate the design limitation for a high efficiency. Moreover, the proposed converter can achieve not only the small conduction loss and the optimal design for high efficiency, but also high power density and low cost due to the switch integration technique. The validity of the proposed converter is confirmed by the experimental results of a prototype converter with 36–72 VDC input and 300 W (12 V/25 A) output.

Active clamped current-fed full-bridge integrating LLC converter with low current and voltage stress

This paper presents an active clamped current-fed full-bridge converter integrating LLC converter for fuel cell power system. In the proposed converter, the half-bridge LLC converter is integrated into the conventional active clamped current-fed full-bridge (ACCF) converter without additional active components and volume increasing. The proposed converter has a low voltage stress on the primary switches because a high step-up voltage conversion ratio can be realized with the low duty ratio D. In addition, due to two transformers structure, the conduction loss of main switches (S1-S4) is decreased by reducing of the peak current. Moreover, the turn-off and conduction losses of auxiliary switch (Saux) are reduced by sinusoidal shape resonant current of the LLC resonant tank. To verify the performance of the proposed converter, the prototype converter with 36V-57V input and 400V/1kW output is implemented.

Asymmetric half-bridge resonant converter having a reduced conduction loss for DC/DC power systems with a low input voltage

A new asymmetric half-bridge (HB) resonant converter for DC/DC power system with a low and wide input voltage is proposed in this paper. The proposed converter is based on the switch integration technique, merging the Active-Clamp Forward (ACF) circuit and the HB LLC resonant converter. By adopting the ACF circuit in front of the HB LLC resonant converter, higher input voltage of LLC resonant converter stage can be achieved. As a result, the primary conduction loss can be significantly reduced. In addition, an asymmetric pulse width modulation (APWM) control is applied to cover wide input voltage range and to mitigate the design limitation for a high efficiency and. Consequently, the proposed converter can achieve not only the small conduction loss and the optimal design for high efficiency, but also high power density and low cost due to the switch integration technique. The validity of the proposed converter is confirmed by the experimental results of a prototype converter with 36-72VDC input and 300W (12V/25A) output.

Phase leading input current compensation in digitally controlled critical mode boost PFC

In this paper, a digital control method to compensate a phase leading input current in a critical mode (CRM) boost power factor corrector (PFC) is proposed. In a constant on-time CRM boost PFC, the power factor (PF) decreases both as the input voltage increases and as the output power decreases because of phase leading input current caused by input filter capacitor. However, conventional researches to obtain a high PF in a CRM boost PFC did not concentrate on this phenomenon. Therefore, a new control method to compensate the phase leading input current of a CRM boost PFC is proposed in this paper. Since the proposed control compensates the current in the input filter capacitor, the phase leading input current is effectively reduced. The cause of the phase leading input current, its tendency, the concept of the proposed control and its implementation are discussed. Finally, the proposed control is experimentally verified with a 60Hz 90-230Vrms input and 395V/0.5A output prototype.

A Bridgeless Dual Boost Rectifier With Soft-Switching Capability and Minimized Additional Conduction Loss

A bridgeless dual boost rectifier is proposed to achieve a soft switching for power factor correction circuit. Based on the conventional bridgeless dual boost rectifier, an auxiliary circuit is employed in the proposed converter to perform zero-voltage switching of the main switches and zero-current switching of the auxiliary switches. As a result, switching losses can be significantly reduced. In addition, the design guideline for the optimized turn-on time of the auxiliary switches is presented to minimize the additional conduction loss in the auxiliary circuit. The validity of the proposed converter is confirmed by the experimental results of a prototype converter with 100–240

A simple THD improving method for CCM boost PFC converter under mixed conduction mode operation

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