• Proceedings of the KIEE Conference
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• 2000.11b
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• pp.352-354
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• 2000

The induction motor is a high-efficiency machine when working close to its rated operation point. This paper uses a simple induction motor model that includes iron losses. The model, which only requires the knowledge of conventional induction motor parameters, is referred to a field-oriented frame. At steady-state light-load condition the minimum point of the input power can be found with the condition that it is possible to obtain the same torque with different combinations of flux and current values. Using the minimum point. the drive system with the proposed efficiency optimization controller can be controlled easily. Simulation and experimental results show the effectiveness of the control strategy proposed for an induction motor drive.

• Journal of Power Electronics
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• v.5 no.4
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• pp.272-281
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• 2005

In this paper, a simple power control scheme for a constant frequency Class-D inverter with a variable duty cycle is proposed. It is more suitable and acceptable for high- frequency induction heating (IH) jar applications. The proposed control scheme has the advantages of not only wide power regulation range but also ease of control output power. Also it can achieve a stable and efficient Zero-Voltage-Switching (ZVS) in a whole load range. The control principles of the proposed method are described in detail and its validity is verified through simulated and experimental results on 42.8kHz IGBT for induction heating rated on 1.6kW with constant frequency variable power.

• The Transactions of the Korean Institute of Power Electronics
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• v.1 no.1
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• pp.27-37
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• 1996

This paper proposes the control algorithm for maximum efficiency drive of PWM inverter - induction motor system with high dynamic performance. If the induction motor is driven under light load with rated magnetizing current, the Iron loss is excessively large compared with the codder loss which results in doer motor efficiency. Maximum efficiency drive of an induction motor can be achieved by controlling the magnetizing current to satisfy the optimal ratio that leads the total motor loss to be a minimum value at a given speed. The proposed control algorithm essentially uses vector control technique and adopts voltage decoupling control strategy to prevent the degradation of dynamic performance due to reduced magnetizing current. To verify the proposed method, digital simulations and experiments are carried out for a squirrel-cage induction motor with the rating of 2.2[kW].

• Proceedings of the KIPE Conference
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• 2008.10a
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• pp.100-102
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• 2008

As Utility interactive fuel cell systems are widely used, it is required for each power conditioning system(PCS) to have higher generating performance and more stable connecting characteristics. This study is focused to minimization of power losses and hence higher efficiency related to the new half bridge type 3-stage utility interactive PCS topology. The loss factor of half-bridge converter becomes only 1.2[%] under the rated load, and hence total efficiency is maintained to be higher as 91[%].

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.689-691
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• 1993

This paper describes an induction heating system which is developed for CRT manufacturing. This system consists of a buck chewer, a voltage source full-bridge inverter, and a series resonant circuit with a matching transformer. A series resonant scheme is employed, and operated at the zero phase of the resonant load by PLL. This ensures maximum power transfer, good efficiency and reliability of the system. Implementation of a prototype rated of 3 kW 450 kHz is described and experimental results are given.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1537-1539
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• 2005

This paper proposes 210[kVA] rated SIV(Static Inverter) system for the TTX(Tilting Train eXpress). The SIV provides power of a fluorescent light in the car, Air-conditioner, and other equipments. To control output voltage it is used voltage control loop for constant voltage control and simultaneously used current control loop for instantaneous control at load changing. The performance of SIV system will be verified by simulation and experimental results.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1416-1418
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• 2005

This paper presents a new hybrid control method of asymmetrical half-bridge converter(AHBC) with low voltage stresses of the diodes and interleaved PFC(power factor correction). The proposed new control scheme can observe variation of secondary diodes voltage stresses by variation of duty ratio and then decide the control portions which are asymmetrical control and PFM(Pulse Frequency Modulation). Therefore, the proposed control scheme has many advantages such as a low rated voltage of the secondary diodes, low conduction loss according to the low voltage drop and wide zvs range by load variation. Through simulation results, the validity of the proposed control scheme is demonstrated.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.6 s.171
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• pp.47-54
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• 2005

A dangerous event occurred at the field industry and mechanical system. At developed by SUNGGOKNANOTECH corp. a R-L clutches of a small and high capacity serves safety device from a variety environment of mechanical system, it permits transmission of driving torque from input to output shaft in both directions of rotation, but restrains any feedback torque of the driven load from rotating the output shaft in either direction. This study was carried out to demonstrate through finite element method and durability estimation for safety of the R-L clutches without sliding during the engagement process. As results, we organized about endurance test method when applied rated torque.

• Journal of the Semiconductor & Display Technology
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• v.17 no.4
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• pp.56-61
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• 2018

In this paper, a new type of active snubber was proposed to lower the excessive rated voltage of the clamp capacitor which was a problem in the conventional circuit by applying auxiliary winding into the active snubber. A simplified equivalent circuit of the proposed snubber was derived by applying it to QR flyback converter, and the equivalent circuits for each switch state was shown under the steady-state condition. In addition, the maximum voltage of the clamp capacitor as well as the main switch was found by using the steady-state equations. In particular, it was found that the clamp capacitor voltage could be controlled by the auxiliary winding ratio. In order to verify the utility and practicality of the proposed converter with auxiliary winding type active snubber circuit, a prototype with an output voltage of 19V and a maximum load current of 6A was produced and the results were reported.

• Journal of Power Electronics
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• v.19 no.1
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• pp.1-10
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• 2019

Current imbalance is the main factor affecting the lifespan of light-emitting diode (LED) lighting systems and is generally solved by active or passive approaches. Given many new lighting applications, independent control is particularly important in achieving different levels of luminance. Existing passive and active approaches have their own limitations in current sharing and independent control, which bring new challenges to the design of LED drivers. In this work, a multichannel resonant converter based on switched-capacitor control (SCC) is proposed for solving this challenge. In the resonant network of the upper and lower half-bridges, SCC is used instead of fixed capacitance. Then, the individual current of the LED array is obtained through regulation of the effective capacitance of the SCC under a fixed switching frequency. In this manner, the complexity of the control unit of the circuit and the precision of the multichannel outputs are further improved. Finally, the superior performance of the proposed LED driver is verified by simulations and a 4-channel experimental prototype with a rated output power of 20 W.