• Korean Journal of Food Science and Technology
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• v.39 no.5
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• pp.506-514
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• 2007

In this study, carrot juice was treated with high voltage pulsed electric fields (PEF) and the changes in its physical and chemical properties during storage at $4^{\circ}C$ and $25^{\circ}C$ were investigated. The sterility fur bacteria, yeast and mold in carrot juice increased with increasing electric field strength and treatment temperature. While yeast and mold were completely inactivated at 65kV/cm with a treatment time of $200{\mu}s$ in a continuous PEF treatment system, bacteria were reduced by four log cycles. The results also showed that square wave pulse treatment was more effective for inactivating microorganisms than exponential decay pulse, and this effect was more apparent for carrot juice of lower pH. Although we observed significant changes in physical and chemical properties such as soluble solid content, pH, acidity, color, and carotene retention when the PEF treated samples were stored at the ambient temperature $(20^{\circ}C)$, no significant physical and chemical changes were found at the cold storage temperature $(4^{\circ}C)$ during 28 days of storage. The results indicate that the PEF treated carrot juice is appropriate for commercial refrigerated storage.

• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1515-1527
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• 2018

This paper presents a sensorless speed control of IPMSM (Interior Permanent Magnet Synchronous Motor) using the high-frequency (HF) square wave injection method. In the proposed HF pulsating square wave injection method, injection voltage is applied into the estimated d-axis of rotor and high-frequency induced q-axis current is considered to estimate the rotor position. Conventional square wave injection methods may need complex demodulation process to find rotor position, while in the proposed method, an easy demodulation process based on the rising-falling edge of the injected voltage and carrier induced q-axis current is implemented, which needs less processing time and improves control bandwidth. Unlike some saliency-based sensorless methods, the proposed method uses maximum torque per ampere (MTPA) strategy, instead of zero d-axis command current strategy, to improve control performance. Furthermore, this paper directly uses resultant d-axis current to detect the magnet polarity and eliminates the need to add an extra pulse injection for magnet polarity detection. As experimental results show, the proposed method can quickly find initial rotor position and MTPA strategy helps to improve the control performance. The effectiveness of the proposed method and all theoretical concepts are verified by mathematical equations, simulation, and experimental tests.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.7
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• pp.916-922
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• 2014

Diode rectifiers have been widely used for an AC to DC converter. But a big problem is that they include large harmonics components in the input currents. A 12-pulse configuration with phase shifting transformer is useful for reducing them. however, it still includes the ($12{\pm}1$)th (m; integer) harmonics in the input currents. In this paper, we propose a single-phase square wave auxiliary voltage supply which is inserted in the middle DC bus. It reduces harmonics especially the 11th and 13th and the harmonic characteristic becomes almost equivalent to a 24-pulse rectifier. Theoretical analysis of the combined 12-pulse diode rectifier with the auxiliary supply is presented and a control method of the auxiliary supply is proposed. The reduction in the input current harmonics is verified by simulation using software PSIM.

• Journal of the Korean Institute of Telematics and Electronics
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• v.9 no.3
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• pp.1-8
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• 1972

The characteristics of tunnel diode pair circuit biased within the negative resistance region has also the voltage-control type negative resistance region, and the voltage at the center point of negative resistance region is described as the square-wave relaxation oscillation. In this paper, the period T, positive duration T1, negative duration T2 of the pulse are obatined from the characteristic curve T, positive duration T1, negative duration T2 of the pulse are obtained from the characteristic curve and observed actually, considring the fact that the pulse width and the period of square-wave at the center point of the negative resistance region is able to be controlle dby the blas volgate. Mereover, the relationship between T, T1 or T2 and circuit parameters is searched for and the Circuit parameters that satisfy the conditions of T1-T2 being proportional to the variation of bias voltage with Teonstant are determined. Thereafter, the bias voltage and the signal voltage are inserted serially to the PWM circuit and the characteristics of that circuit is analyzed.

• Proceedings of the KIEE Conference
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• 1999.11c
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• pp.693-696
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• 1999

This paper describes a new voltage recorder for the voltage management of a power distribution line by using a new voltage measurement technique. The RMS(Root Mean Square) voltage measurement for the power line under the assumption of a sinusoidal input voltage is taken by the full-wave rectifier, half-adder utilizing operational amplifier(OP) circuit. A/D converter utilizing a dual slope converter converts an analog voltage signal into a serial pulse. The pulse is counted with a single chip micro-controller, converted with the RMS voltage, and saved into a flash memory. In the last, a new voltage recorder with compact size and multifunction is developed. Also, Voltage Management System that can analyze the stored data via RS-232C cable is developed based on Windows 95 and Visual C++.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2005.11a
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• pp.119-122
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• 2005

A algorithm for control and performance of a pulse-density-modulated (PDM) series-resonant voltage source inverter developed for corona-dischange precesses is presented. The PDM inverter produces either a square-wave ac-voltage state or a zero-voltage state at its ac terminals to control the average output voltage under constant dc voltage and operating frequency. Moreover it can achieve zero-current-switching (ZCS) and zero-voltage-switching (ZVS) in all the operating condition for a reduction of switching lost. Even though the corona discharge load with a strong nonlinear characteristics, new high frequency resonant inverter is shown the wide range power control from 5% to 100%.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.464-468
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• 1999

This paper deals with the harmonic reduction technique in square-wave inverters which can regenerate the dc power from dc bus line to ac bus line in substations for traction systems. To reduce the harmonics, two 6-pulse inverters are used for 12-pulse operation and zigzag-connected output transformers for eliminating the harmonics of 6(2m-1)$\pm$1 orders. And an ac filter is furnished at output side. In spite of the square-wave three-phase inverters, computer simulations show that the THDs of the output voltage and current are 2.55% and 0.554%, respectively.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.4
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• pp.622-627
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• 2016

This paper describes the development of a portable potentiostat which can perform square wave voltammetry on electrochemical sensors and wireless transmission of the measured data to a smartphone using Bluetooth. The potentiostat consists of a square wave potential pulse generation circuit for applying the potential pulse to the electrochemical sensor, a reduction/oxidation (or redox) current measurement circuit, and Bluetooth for wireless data transmission to an Android-based smartphone. The measured data are then processed to show the output graph on the smart phone screen in real time. This data transformation into a graph is carried out by developing and installing a simple transformation application software in the Android-based smartphone. This application software also enables the user to set and change the measurement parameters such as the applied voltage range and measured current range at user's convenience. The square voltammetry output data measured with the developed portable potentiostat were almost same as the data of the commercial potentiostat. The measured oxidation peak current with the commercial potentiostat was $11.35{\mu}A$ at 0.26 V and the measured oxidation peak current with the developed system was $12.38{\mu}A$ at 0.25 V. This proves that performance of the developed portable measurement system is comparable to the commercial one.

• 전기의세계
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• v.21 no.1
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• pp.17-21
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• 1972

Electrical resistivity and switching phenomena in glass semiconductor of AsTe and AsTeGa is studied. Samples sliced from ingot which is air quenched or water quenched, show high resistivity at room temperature. The resistivity of the AsTe and AsTeGa is 1*10$^{6}$ .ohm.-cm and 5*10$^{6}$ .ohm.-cm at 27.deg. C. Switching phenomena take place in thin the thick samples. Holding voltage is different with the thickness of the samples and the characteristics of switching in the thin and thick samhles are similar. When square wave pulse voltage is applied, delay time is detected to 5.mu.sec by oscilloscpoe.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.8
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• pp.45-51
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• 2000

The distortion of an electrical pulse, which has a rise/fall time due to the dispersion and the reflection, on tapered microstrip lines has investigated In time domain. The voltage and current transfer functions are shown for the tapered line. The dispersion distortion obtained by using these trans(or functions are represented for the nonideal square pulse along the triangular, Tchebycheff and exponential tapered lines, and analyzed the influence of the reflection and the frequency dispersion on the distorted voltage wave in the tapered lines. The observed overshoot in front of the distorted wane is caused due to the frequency dispersion and the sustained tail of that comes from the reflection in the tapered line.