• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.26 no.1
• /
• pp.66-74
• /
• 2012

This paper propose a improved direct torque control(DTC) system for improving operation of five-phase squirrel-cage induction motor(IM). A five-phase IM drives present unique characteristics due to the additional degrees of freedom and also drives possess many others advantage compared with the traditional three-phase motor drive system, such as reducing a amplitude of torque pulsation and increasing the reliability. In order to maximize the torque per ampere, the proposed motor has concentrated windings and the produced back-electromotive force(EMF) is almost trapezoidal, and the motor is supplied with the combined sinusoidal plus third harmonic of currents, there is necessary to controlled 3rd harmonic current. Also a DTC method is advantageous when it is applied to the five-phase IM, because the five-phase inverter provides 32 space vectors in comparison to 8 space voltage vectors into the three-phase inverter drive system. For presenting the superior performance of the proposed DTC, experimental results of speed control are presented using a 32-bit fixed point TMS320F2812 DSP with 1.5[hp] IM.

• Journal of Advanced Marine Engineering and Technology
• /
• v.28 no.2
• /
• pp.382-392
• /
• 2004

The usage of constant velocity (CV) joint is effective for motorboats on gliding regime of the motion. During transition on the gliding when angle of the CV differs from null on driving and driven composite shafts there are moments of the second order. Excitation of oscillations of the second order moments occurs when driving shafts transmits a variable torque. which generates through CV joint a lateral moment acting on the bearing. As a result of oscillations from a resonating harmonic of a shafting the harmonic with the greater or periodically varying amplitude for power condition trough transferring to nominal power 144kW. Beating conditions coincide with third mode having frequency 45.486 Hz. In that case there is high increasing of the equivalent stresses. The forming of the stiffness of the composite material is concerned to use most orientation of the layer angle in the range of $\pm$60 degrees relatively of shaft axis. Application of that angles for layer orientation gives possibility to avoid high disturbance of the shafting for motorboat transition regime.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.20 no.3
• /
• pp.84-89
• /
• 2006

Tripping of residual current protective devices(RCPDs) caused by harmonics has been continuously reported, but no literature is available on the behavior of RCPDs caused by harmonics. This paper, in order to find out the effects of harmonics on RCPDs, investigated the present condition on malfunction of RCPDs and measured harmonics at buildings where nuisance tripping of RCPDs was often occurred. Also, the operational characteristics of RCPDs were tested by the harmonics synthesizer that can generate distorted waveform. Results of experiment detected that there was minimum tripping current of RCPDs when third harmonic added to the fundamental frequency. And it was found that the leakage current to cause tripping of RCPDs increased with more higher order harmonics added to the fundamental frequency.

• Journal of Power Electronics
• /
• v.18 no.5
• /
• pp.1336-1346
• /
• 2018

Wide band gap semiconductor devices such as SiC MOSFETs are becoming the preferred devices for high frequency and high power density converters due to their excellent performances. However, the proportion of the switching loss that accounts for the whole inverter loss is growing along with an increase of the switching frequency. In view of the third quadrant working characteristics of a SiC MOSFET, synchronous rectification discontinuous pulse-width modulation is proposed (SRDPWM) to further reduce system losses. The SRDPWM has been analyzed in detail. Based on a frequency domain mathematical model, a quantitative mathematical analysis of the harmonic characteristic is conducted by double Fourier transform. Meanwhile, a switching loss model and a conduction loss model of inverter for SRDPWM have been built. Simulation and experimental results verify the result of the harmonic analysis of the double Fourier analysis and the accuracy of the loss models. The efficiencies of the SRDPWM and the SVPWM are compared. The result indicates that the SRDPWM has fewer losses and a higher efficiency than the SVPWM under high switching frequency and light load conditions as a result of the reduced number of switching transitions. In addition, the SRDPWM is more suitable for SiC MOSFET converters.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.16 no.11 s.102
• /
• pp.1155-1163
• /
• 2005

In this paper, we suggest the new method to considerably enlarge stopband without increment of filter sire and loss. The proposed low pass filter looks like outward configuration with the published Modified Generalized Chebyshev (MGC) low pass filter, but the element values completely differ from each other. The published MGC fille, had been considered only the second attenuation pole to reject(or suppress) the harmonic, whereas the stopband of the proposed filter is superior to the published MGC filter because not only the second attenuation pole but also the third harmonic of the first attenuation pole is made use of profitably. We fabricate a low pass filter according to the proposed theory. From the measurement of the fabricated filter, we can confirm that the stopband of the proposed filter is reached above 4 times wider than the conventional Generalized Chebyshev(GC) filter and above 1.7 times wider than the published MGC filter.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.26 no.9
• /
• pp.783-789
• /
• 2015

This paper presents a Doherty power amplifier(DPA) operating in the 2.6 GHz band for long term evolution(LTE) systems. In order to achieve high efficiency, second and third harmonic impedances are controlled using a compact output matching network. The DPA was implemented using a gallium nitride high electron mobility transistor(GaN-HEMT) that has many advantages, such as high power density and high efficiency. The implemented DPA was measured using an LTE downlink signal with a 10 MHz bandwidth and 6.5 dB PAPR. The implemented DPA exhibited a gain of 13.1 dB, a power-added efficiency(PAE) of 57.6 %, and an ACLR of -25.7 dBc at an average output power of 33.4 dBm.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.44 no.1
• /
• pp.32-37
• /
• 2007

A DMB CMOS power amplifier (PA) with high efficiency and linearity is present. For this work, a 0.13-um standard CMOS process is employed and all components of the proposed PA are fully integrated into one chop including output matching network and adaptive bias control circuit. To improve the efficiency and linearity simultaneously, an adaptive bias control circuit is adopted along with second harmonic termination circuit at the drain node. The PA is shown a $P_{1dB}$ of 16.64 dBm, power added efficiency (PAE) of 38.31 %, and power gain of 24.64 dB, respectively. The third-order intermodulation (IMD3) and the fifth-order intermodulation (IMD5) have been -24.122 dBc and -37.156 dBc, respectively.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.8 no.4
• /
• pp.330-343
• /
• 2016

This paper presents results of an experimental investigation of vortex-induced vibration (VIV) of a flexibly mounted and rigid cylinder with two-degrees-of-freedom with respect to varying ratio of in-line natural frequency to cross-flow natural frequency, $f^*$, at a fixed low mass ratio. Combined in-line and cross-flow motion was observed in a sub-critical Reynolds number range. Three-dimensional displacement meter and tension meter were used to measure dynamic responses of the model. To validate the results and the experiment system, x and y response amplitudes and ratio of oscillation frequency to cross-flow natural frequency were compared with other experimental results. It has been found that the higher harmonics, such as third and more vibration components, can occur on a certain part of steel catenary riser under a condition of dual resonance mode. In the present work, however, due to the limitation of a size of circulating water channel, the whole test of a whole configuration of the riser at an adequate scale for VIV phenomenon was not able to be conducted. Instead, we have modeled a rigid cylinder and assumed that the cylinder is a part of steel catenary riser where the higher harmonic motions could occur. Through the experiment, we have found that even though the cylinder was assumed to be rigid, the occurrence of the higher harmonic motions was observed in a small reduced velocity ($V_r$) range, where the influence of the in-line response is relatively large. The transition of the vortex shedding mode from one to another was examined by using time history of x and y directional displacement over all experimental cases. We also observed the influence of in-line restoring force power spectral density with $f^*$.

• Journal of Power Electronics
• /
• v.11 no.3
• /
• pp.294-303
• /
• 2011

In this paper an effective five-phase induction motor (IM) and its drive methods are proposed. Due to the additional degrees of freedom, the five-phase IM drive presents unique characteristics for enhancing the torque producing capability of the motor. Also the five-phase motor drives possess many other advantages when compared to traditional three-phase motor drives. Some of these advantages include, reducing the amplitude and increasing the frequency of the torque pulsation, reducing the amplitude of the current without increasing the voltage per phase and increasing the reliability. In order to maximize the torque per ampere, the proposed motor has concentrated winding, the produced back electromotive force (EMF) is almost trapezoidal, and the motor is supplied with the combined sinusoidal plus the third harmonic of the currents. For demonstrating the superior performance of the proposed five-phase IM, the motors are also analyzed on the synchronously rotating reference frame. To supply trapezoidal current waveform and to exclude the effect of the $3^{rd}$ harmonic current, a new control stratagem is proposed. The proposed control method is based on direct torque control (DTC) and rotor flux oriented control (RFOC) of the five-phase IM drives. It is able to reduce the acoustical noise, the torque, the flux, the current, and the speed pulsations during the steady state. The DTC transient merits are preserved, while a better quality steady-state performance is produced in the five phase motor drive for a wide speed range. Experimental results clearly demonstrated a more dynamic steady state performance with the proposed control system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.21 no.9
• /
• pp.987-994
• /
• 2010

In this paper, a simple and effective active load-pull method is proposed, and the method to improve the efficiency of X-band power amplifier using harmonic control circuit is presented. The proposed active load-pull system mainly consists of directional coupler, phase shifter, short circuit, and power amplifier, and allows a user to access reflection coefficients near the edge of the Smith chart($\Gamma$=1) easily. The device used in this paper is Mitsubishi's GaAs FET MGF1801, and the operating frequency of the power amplifier is 9 GHz, The amplifier had output power of 21.65 dBm and drain efficiency of 24.9 % at class-A, and had output power of 21.46 dBm and drain efficiency of 53.3 % at class-AB. Harmonic control circuit is designed only second and third harmonic components because of the bandwidth limitation of the microwave components. The drain efficiency is improved as much as 6.4 % compared with class-AB power amplifier.