• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.1
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• pp.101-110
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• 2002

A method to control the inverter output voltage lineally in over modulation mode of the third harmonics injected PWM inverter is proposed. The third harmonics injected PWM has a extended linear region compared with the sine PWM. But it still has a maximum voltage about 90% compared with the six step inverter. Therefore, to control the output voltage linearly in over modulation mode, analyzing the relationship between the modulation index and the peak of the fundamental component of the modified reference voltage, we can settle the problem in over modulation mode without iteration. Then we can increase the maximum fundamental component of the third harmonics injected PWM inverter comparative to six-step inverter continuously in over modulation mode. The simulation results of the inverter-induction motor system shows the validity of this method and experimental results prove it.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.5
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• pp.423-431
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• 2001

This paper proposes a new active common-mode voltage damper circuit that is capable of suppressing a common-mode voltage produced in the PWM VSI-fed induction motor drives. The new active common mode voltage damper is consists of a four-level half-bridge Inverter and a common mode transformer with a blocking capacitor. In order to reduce the common mode voltage and high frequency leakage current the active common mode damper applies to the PWM inverter system the compensated voltage of which the amplitude is the same as the common mode voltage and of which the polarity is opposite to the common mode voltage. Simulated using P-SPICE and experimental results show that common-mode voltage damper makes contributions to reducing a high frequency leakage current and common-mode voltage.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.9
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• pp.72-80
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• 2009

When the magnet wheel rotates over a conducting plate, it generates the traction torque as well as the repulsive force on the conducting plate. Partially-cut traction torque results in the linear force into the tangential direction. To cut the traction torque, the concept of magnetic shield is introduced. The direction change of the linear force is realized varying the shielded area of magnetic field. That is, the tangential direction of non-shielded open area becomes the direction of the linear thrust force. Specially a shape of permanent magnets composing the magnet wheel leads to various pattern of magnetic forces. So, to enlarge the resulting force density and compensate its servo property a few simulations are performed under various conditions such as repeated pattern, pole number, radial width of permanent magnets, including shape of open area. The theoretical model of the magnet wheel is derived using air-gap field analysis of linear induction motor, compared with test result and the sensitivity analysis for its parameter change is performed using common tool; MAXWELL. Using two-axial wheel set-up, the tracking motion is tested for a copper plate with its normal motion constrained and its result is given. In conclusion, it is estimated that the magnet wheel using partial shield can be applied to a noncontact conveyance of the conducting plate.

• Journal of KIISE:Software and Applications
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• v.30 no.11
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• pp.1044-1053
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• 2003

A virtual science experience space(VSES) using virtual reality technology including haptic device is proposed to overcome limits which the existing science education has and to improve the effect of it. Four example scientific worlds such as Micro World, Friction World, Electromechanical World and Macro World are demonstrated by the developed VSES. Van der Waals forces in Micro World and Stick-Slip friction in Friction World, the principle of induction motor and power generator in Electromechanical World and Coriolis acceleration that is brought about by relative motion on the rotating coordinate are modeled mathematically based on physical principles. Emulation methods for haptic interface are suggested. The proposed VSES consists of haptic device, HMD or Crystal Eyes and a digital computer with stereoscopic graphics and GUI. The proposed system is believed to increase the realism and immersion for user.

• Journal of Power Electronics
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• v.18 no.6
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• pp.1729-1750
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• 2018

Voltage source inverters (VSIs) are widely used to drive induction motors in industry applications. The quality of output waveforms depends on the switching sequences used in pulse width modulation (PWM). In this work, all existing optimal space vector pulse width modulation (SVPWM) switching strategies are studied. The performance of existing SVPWM switching strategies is optimized to realize a tradeoff between quality of output waveforms and switching losses. This study generalizes the existing optimal switching sequences for total harmonic distortions (THDs) and switching losses for different modulation indexes and reference angles with a parameter called quality factor. This factor provides a common platform in which the THDs and switching losses of different SVPWM techniques can be compared. The optimal spatial distribution of each sequence is derived on the basis of the quality factor to minimize harmonic current distortions and switching losses in a sector; the result is the minimum ripple loss SVPWM (MRSLPWM). By employing the sequences from optimized switching maps, the proposed method can simultaneously reduce THDs and switching losses. Two hybrid SVPWM techniques are proposed to reduce line current distortions and switching losses in motor drives. The proposed hybrid SVPWM strategies are MRSLPWM 30 and MRSLPWM 90. With a low-cost PIC microcontroller (PIC18F452), the proposed hybrid SVPWM techniques and the quality of output waveforms are experimentally validated on a 2 kVA VSI based on a three-phase two-level insulated gate bipolar transistor.

• YAKHAK HOEJI
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• v.44 no.5
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• pp.470-477
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• 2000

WooHwangChungSimWon is a traditional medicine for treatment of hypertension, arteriosclerosis, coma, and stroke in China, Korea, and Japan. In the new prescription of WooHwangChungSimWon, the civet is substituted for the musk, the major component of WooHwangChungSimwon, because of the prohibition law about the musk. We have made a comparative study of the effects on the central nervous system between the musk containing and civet containing WooHwangChungSimWon. In order to investigate the effects on the central nervous system, we have examined spontaneous motor activities, anti-convulsion activities induced by chemicals or electric shock, sleep induced by hexobarbital, and antistress effects. In the examination of anti-convulsion effects against the electric shock and injection of pentetrazol, only the civet containing WooHwangChungSimWon showed the anti-convulsion effects, i.e. the duration of convulsion by electric shock was decreased (control: 104.0 seconds, low dose of civet containing WooHwangChungSimWon: 60.7 seconds) and the duration of suppression against pentetrazol induced convulsion was increased (control: 392.3 seconds, low dose of civet containing WooHwangChungSimWon: 574.0 seconds, high dose of civet containing WooHwangChungSimWon: 561.4 seconds). In the other examinations, all kinds of WooHwangChungSimWon showed sedation, anti-convulsion activities, and induction of sleeping. These results suggest that there are no significant differences between the musk containing and civet containing WooHwangChungSimWon except the anti-convulsion effects against the convulsions induced by electric shock and pentetrazol.

• Journal of the Korean Society for Railway
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• v.11 no.5
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• pp.477-481
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• 2008

This paper dealt with a detection method of series arc existence which is a symptom of electric fires in low-voltage system. The proposed detection circuit consists of a high-pass filter with a low cut-off frequency of 3kHz to attenuate power frequency voltage by 80 dB and an active band-pass filter with a center frequency of 4kHz to detect only the series arc signals. The performance of the circuit was evaluated in a phase-controlled incandescent lamp as a non-linear load and an inverted-fed induction motor as a high frequency load by using the arc generator specified in UL1699. From the experimental results, it was confirmed that the proposed method solved the detection error, which is being the most problem, by discriminating the series arc signal even in non-linear and high frequency loads.

• Journal of Power Electronics
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• v.19 no.3
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• pp.702-713
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• 2019

Multilevel Inverters (MLIs) are widely used in medium voltage applications due to their various advantages. In addition, there are numerous types of MLIs for such applications. However, the diode-less 3-level (3L) T-type Neutral Point Clamped (NPC) MLI is the most advantageous due to its low conduction losses and high potential efficiency. The power circuit of a 3L T-type NPC is derived by the conventional two level inverter by a slight modification. In order to explore the MLI performance for various Pulse Width Modulation (PWM) schemes, this paper examines the operation of a 3L (five level line to line) T-type NPC MLI for various types of Multi-Carriers Pulse Width Modulation (MCPWM) schemes. These PWM schemes are compared in terms of their voltage profile, total harmonic distortion (THD) and conduction losses. In addition, a 3L T-type NPC MLI is also compared with the conventional NPC in terms of number of switches, clamping diodes, main diodes and capacitors. Moreover, the capacitor-balancing problem is also investigated using the Neutral Point Fluctuation (NPF) method with all of the MCPWM schemes. A 1kW 3L T-type NPC MLI is simulated in MATLAB/Simulink and implemented experimentally and its performance is tested with a 1HP induction motor. The results indicate that the 3L T-type NPC MLI has better performance than conventional NPC MLIs.

• Biomolecules & Therapeutics
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• v.29 no.6
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• pp.615-629
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• 2021

An active compound, triterpene saponin, astersaponin I (AKNS-2) was isolated from Aster koraiensis Nakai (AKNS) and the autophagy activation and neuroprotective effect was investigated on in vitro and in vivo Parkinson's disease (PD) models. The autophagy-regulating effect of AKNS-2 was monitored by analyzing the expression of autophagy-related protein markers in SH-SY5Y cells using Western blot and fluorescent protein quenching assays. The neuroprotection of AKNS-2 was tested by using a 1-methyl-4-phenyl-2,3-dihydropyridium ion (MPP⁺)-induced in vitro PD model in SH-SY5Y cells and an MPTP-induced in vivo PD model in mice. The compound-treated SH-SY5Y cells not only showed enhanced microtubule-associated protein 1A/1B-light chain 3-II (LC3-II) and decreased sequestosome 1 (p62) expression but also showed increased phosphorylated extracellular signal-regulated kinases (p-Erk), phosphorylated AMP-activated protein kinase (p-AMPK) and phosphorylated unc-51-like kinase (p-ULK) and decreased phosphorylated mammalian target of rapamycin (p-mTOR) expression. AKNS-2-activated autophagy could be inhibited by the Erk inhibitor U0126 and by AMPK siRNA. In the MPP⁺-induced in vitro PD model, AKNS-2 reversed the reduced cell viability and tyrosine hydroxylase (TH) levels and reduced the induced α-synuclein level. In an MPTP-induced in vivo PD model, AKNS-2 improved mice behavioral performance, and it restored dopamine synthesis and TH and α-synuclein expression in mouse brain tissues. Consistently, AKNS-2 also modulated the expressions of autophagy related markers in mouse brain tissue. Thus, AKNS-2 upregulates autophagy by activating the Erk/mTOR and AMPK/mTOR pathways. AKNS-2 exerts its neuroprotective effect through autophagy activation and may serve as a potential candidate for PD therapy.

• Journal of Korean Society of Transportation
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• v.19 no.4
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• pp.35-47
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• 2001

Traffic represents one of the largest sources of primary air pollutants in urban area. As a consequence. numerous abatement strategies are being pursued to decrease the ambient concentration of pollutants. A characteristic of most of the these strategies is a requirement for accurate data on both the quantity and spatial distribution of emissions to air in the form of an atmospheric emission inventory database. In the case of traffic pollution, such an inventory must be compiled using activity statistics and emission factors for vehicle types. The majority of inventories are compiled using passive data from either surveys or transportation models and by their very nature tend to be out-of-date by the time they are compiled. The study of current trends are towards integrating urban traffic control systems and assessments of the environmental effects of motor vehicles. In this study, a methodology of motor vehicle emission calculation by using real-time traffic data was studied. A methodology for estimating emissions of CO at a test area in Seoul. Traffic data, which are required on a street-by-street basis, is obtained from induction loops of traffic control system. It was calculated speed-related mass of CO emission from traffic tail pipe of data from traffic system, and parameters are considered, volume, composition, average velocity, link length. And, the result was compared with that of a method of emission calculation by VKT(Vehicle Kilometer Travelled) of vehicles of category.