• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.14 no.6
• /
• pp.638-647
• /
• 2003

Triangular patches have been studied, both theoretically and experimentally. We feund that provided radiation characteristics similar to those of rectangular patches, but with smaller size. In this paper, we designed an equilateral triangular microstrip patch antenna using cavity model analysis. Then, in order to improve narrow bandwidth, we add capacitive gap and air gap. Capacitive gap is located with square shape beside feeding point on the patch, and air gap is inserted between substrate dielectric and ground plane to adjust probe inductance. The analysis of characteristics and effects of each component was performed by commercial simulation tool, Ensemble 5.0. Throughout the simulation and experiment, we found the possibility of bandwidth enhancement in triangular microstrip antenna.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.3 no.3
• /
• pp.263-272
• /
• 1998

This paper presents the new control strategy that can minimizes the torque ripple by considering the magnetic nonlinearity and phase torque averlapping intervals, and describes the whole SRM drive system using proposed control method implemented by DSP(Digital Signal Processor). To do this, inductance and torque are, at first, measured according to the variation of rotor position angle while current is kept constant at predetermined several values. From these measured values, the entire inductance and torque for any current and rotor position are inferred by using neural network. And the waveform of the reference phase torque is determined for the torque ripple to be minimized considering the torque overlap between phases. The controller is designed for the actual torque obtained by the inferred torque look-up table using measured current and rotor position angle to track the predetermined reference phase torque by delta modulation technique. To perform a real time processing and ensure the reliability of the controller, DSP is implemented.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.18 no.3 s.118
• /
• pp.265-272
• /
• 2007

In this paper, a frequency changeable antenna using dual half wavelength loaded line structure is proposed for multiband mobile handset applications. The proposed antenna has a capability of independent frequency shift by controlling two added inductance values in two different bands. Experimental results indicate that the proposed antenna provides enough effective bandwidth to cover $CELLULAR(824\sim894\;MHz)$, $EGSM(880\sim960\;MHz)$, $DCS1800(1,710\sim1,880\;MHz)$, $PCS1900(1,850\sim1,990\;MHz)$ and $WCDMA(1,920\sim2,170\;MHz)$ bands and peak gain variation is only 0.54 dB.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.55 no.7
• /
• pp.339-343
• /
• 2006

In this study, the variations of the important characteristics of solenoid-type RF chip inductors utilizing a low-loss A1203 core material on inductor dimensions were investigated systematically. Four dimensions of the chip inductors fabricated in this work were $1.0\times0.5\times0.5mm^3,\;1.5\times1.0\times0.7mm^3,\;2.1\times1.5\times1.0mm^3,\;and\;2.4\times2.0\times1.4mm^3$ and copper (Cu) wire with $40{\mu}m$ diameter was used as the coils. High frequency characteristics of the inductance, quality factor, and impedance of developed inductors as a function of inductor dimensions were measured using an RF Impedance/Material Analyzer (HP4291B with HP16193A test fixture). It was observed that the developed inductors with the number of turns of 6 have the inductance (L) of 12 to 82 nH and exhibit the self-resonant frequency (SRE) of 3.6 to 1.2 GHz. The SRF of inductors decreases with increasing the inductor size while the L increases with the inductor size. The smallest inductors of $1.0\times0.5\times0.5mm^3$ exhibited the L of 12 nH, SRF of 3.6 GHz, and the quality factor of 67 near the frequency of 1.1 GHz. The calculated data predicted the high-frequency data of the L, and Q of the developed inductors well.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.26 no.4
• /
• pp.389-396
• /
• 2015

A coil design of pulse induction metal detectors has been described. The search coil was demonstrated by using the wire with the diameter of 0.3 mm, 0.5 mm and 1.0 mm and the dielectric plate with the $30cm{\times}30cm$ and $35cm{\times}35cm$, the time constant and the currents of the coil as the variation of the coil size and the number of coil turns was characterized. The coil parameters like the resistance, the inductance and the time constants as the variation of the diameter of the wire, the coil size and the number of coil turns were compared and analysed through the calculation and the measurement. In addition, investigating the coil currents as the variation of the input pulse width, the coil design of pulse induction metal detectors has been discussed.

• Journal of Advanced Navigation Technology
• /
• v.19 no.3
• /
• pp.237-243
• /
• 2015

This paper presented the design of wireless power transfer (WPT) system using electromagnetic induction techniques and analysed WPT efficiency. Also, we presented the optimum coil condition by measuring the efficiency variation according to some receiving coil parameter changes. Voltage change is measured by receiving coil position for the designed transmitting and receiving circuit. Voltage change according to inductance variation at the same position and charging time are compared at the same environment by using a developed application program to realize an optimum WPT system. Developed wireless power transfer system using electromagnetic induction techniques uses 125 kHz. It takes 16 minutes by using wired charger, and 23 minutes by using wireless charger for charging from 50% to 60% charging status.

• Journal of the Korean Institute of Telematics and Electronics T
• /
• v.36T no.3
• /
• pp.56-63
• /
• 1999

In this paper, we realize the active PFC(Power Factor Correction) system of BF (Boost Forward) converter with PWM-PFM control technique to control DC output voltage, and to control the input current with sinusoidal wave synchronized by the converter and inverter using power switching element, FET and IGBT. The control circuit of the suggested Boost converter is implemented with a microprocessor 80C196. After making the ratio of output voltage to current as 50V/1A and the duty ratio greater than 0.5. When input voltage is 30V and boost inductance is 1.1mH. We control the voltage changing rate according to the variation of load resistance using a PWM-PFM control technique. And finally we prove experimentally. PF can be improved up to 0.96 using the current shaping technique.

• Journal of Power Electronics
• /
• v.15 no.5
• /
• pp.1264-1273
• /
• 2015

An inverter output power control based power factor correction (PFC) strategy is being extensively used for permanent magnet synchronous motor (PMSM) drives in appliances because such a strategy can considerably reduce the cost and size of the inverter. In this strategy, PFC circuits are removed and large electrolytic DC-link capacitors are replaced with small film capacitors. In this application, the PMSM d-q axes currents are controlled to produce ripples, the frequency of which is twice that of the AC main voltage, to obtain a high power factor at the AC mains. This process indicates that the PMSM operates under periodic magnetic saturation conditions. This paper proposes a back electromotive-force (back-EMF) estimator for the high-speed sensorless control of PMSM operating under periodic magnetic saturation conditions. The transfer function of the back-EMF estimator is analyzed to examine the effect of the periodic magnetic saturation on the accuracy of the estimated rotor position. A simple compensation method for the estimated position errors caused by the periodic magnetic saturation is also proposed in this paper. The effectiveness of the proposed method is experimentally verified with the use of a PMSM drive for a vacuum cleaner centrifugal fan, wherein the maximum operating speed reaches 30,000 rpm.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.65 no.9
• /
• pp.1626-1631
• /
• 2016

Generally, the low-voltage customer has been used with a linear load and nonlinear load in the 3-phase 4-wire distribution system. Linear load has usually configured the resistance and inductance, current phase is slower than the voltage phase, so power factor is low. It is required for the power factor correction device prior to the phase of the current than the voltage. The capacitor is connected in parallel to the load in order to ensure a low power factor. Power converter such as an inverter is a typical non-linear load. Non-linear load generates harmonic currents in the energy conversion process. Many electrical equipment may be adversely affected by the harmonic current. There, passive or active filter have been used to reduce these harmonics current. Passive filter consisting of inductor and capacitor generates a reactive power. According to the combination of filter inductor and capacitor, reactive power can be adjusted. In this paper, we analyzed how the combination of inductor and capacitor affects the overall power factor by simulation and measurement.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.54 no.11
• /
• pp.533-539
• /
• 2005

In the previous work, we performed the analysis of a tubular type moving-magnet linear oscillatory actuator (LOA) with cylindrical Halbach array by using 2-d analytical formulas and confirmed validity of analytical results by comparison of those with both finite element (FE) computation and experimental results. This paper deals with the dynamic characteristic analysis of the moving-magnet LOA with cylindrical Halbach array. Control parameters such as the thrust constant, the back-emf constant, resistance and inductance are obtained from both analytical and experimental results. And then, the dynamic simulation algorithm is established by the state and output equation obtained from voltage and motion equation. Finally, for various values of frequency, the dynamic simulation and experimental results for the characteristics of the voltage, current and displacement of moving-magnet LOA are presented. The simulation results are validated extensively by experiments. The experimental and simulation results for the variation of stroke according to control voltage are also presented for various values of frequency.