• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.12
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• pp.1732-1736
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• 2014

Generally, traction motors for railway vehicles are inferior to that of electric vehicle in terms of output density. Traction motors for railway vehicles are relatively free of spatial constraints than motors electric vehicles, but in terms of whole system efficiency, increasing output density of traction motor is helpful. In this paper, using Halbach magnet array structure, output density of traction motor for 40kW class tram was elevated. This paper introduce detailed design process of the Halbach magnet array structure applied model, and check the affects on output characteristics by parameters like rotor shape, airgap diameter and pole ratio. Also, electrical output characteristics were compared between typical SPMSM model and Halbach magnet array model, which has same output size.

• Journal of Korean Institute of Industrial Engineers
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• v.31 no.3
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• pp.257-264
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• 2005

This paper suggests a heuristic algorithm for the clustering problem. Clustering involves grouping similar objects into a cluster. Clustering is used in a wide variety of fields including data mining, marketing, and biology. Until now there are a lot of approaches using Self-Organizing Feature Maps(SOFMs). But they have problems with a small output-layer nodes and initial weight. For example, one of them is a one-dimension map of k output-layer nodes, if they want to make k clusters. This approach has problems to classify elaboratively. This paper suggests one-dimensional output-layer nodes in SOFMs. The number of output-layer nodes is more than those of clusters intended to find and the order of output-layer nodes is ascending in the sum of the output-layer node's weight. We can find input data in SOFMs output node and classify input data in output nodes using Euclidean distance. We use the well known IRIS data as an experimental data. Unsupervised clustering of IRIS data typically results in 15 - 17 clustering error. However, the proposed algorithm has only six clustering errors.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.40
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• pp.33-63
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• 2008

This study introduces the adoption of the logistics industry by the Korean government as a threshold of overcoming economic difficulties. The core contents of the National Logistics Plans (2001-2020) which contain the basic principles of the logistics policies of the Korean government and its aim to be an 'Excellent Nation of Logistics' is introduced. The economic effect of the logistics policies implemented between 2001 and 2005, (the period of the first Medium-term Logistics Plan according to the National Logistics Plans (2001-2020) set up by the Korean government at the end of 2000) is estimated through input-output analysis. The input-output analysis result is as follows: the total output effect is 8,856 billion won of which indirect output effect is 3,982.9 billion won; indirect output effect comes mainly from real estate and business services, non-metal products, metal products, electrical and electronics products, finance and insurance, wholesale and retail, petroleum and coal; the total amount of value-added effect is 3,376 billion won and total import effect is 726 billion won. Employment effect including self-employed and unpaid family supporters with paid laborers is 79,203.7 people of which paid laborers comprise 67,547.7 people.

• Journal of Power Electronics
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• v.14 no.5
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• pp.908-917
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• 2014

For the purpose of designing an intrinsic safety Flyback converter with minimal output voltage ripple based on a specified output current, this paper first classified the energy transmission modes of the system into three sorts, namely, the Complete Inductor Supply Mode-CCM (CISM-CCM), the Incomplete Inductor Supply Mode-CCM (IISM-CCM) and the Incomplete Inductor Supply Mode-DCM (IISM-DCM). Then, the critical secondary self-inductance assorting the three modes are deduced and expressions of the output voltage ripples (OVR) are presented. For a Flyback converter with constant loads and switching frequency, it is shown that the output voltage ripple in the CISM-CCM is the smallest and that it has no relationship with the secondary self-inductance. Otherwise, the OVR of the other two modes are bigger than the previously mentioned one. It is concluded that the critical inductance between the CISM-CCM and the IISM-CCM is the minimal secondary self-inductance to ensure the smallest output voltage ripple. At last, a design method to guarantee the minimum OVR within the scales of the input voltage and load are analyzed, and the minimum secondary self-inductance is proposed to minimize the OVR. Simulations and experiments are given to verify the results.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.3
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• pp.54-59
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• 2008

A highly accurate wide swing BiCMOS cascode current mirror is proposed. It uses the base-current compensated BJT current mirror. It increases both output impedance and output voltage range by using the npn-NMOS cascode instead of the NMOS-NMOS cascode. The npn transistor copies the input current and the NMOS transistor increases the output impedance for the accurate current mirroring. The proposed current mirror achieves highly constant current for wide output voltage range. Simulation results were verified with measurements performed on a fabricated chip using a 5/16V 0.5um BCD process. It has only $-2.5%{\sim}1.0%$ current error for $0.3V{\sim}16V$ output voltage range.

• Journal of the Korean Society for Railway
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• v.11 no.4
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• pp.410-416
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• 2008

The inter-industrial inducement effects of the korean railway services on the output, value-added, imports of the 403 industrial sectors of the korean economy have been computed by the input-output analysis technique utilizing the 2003 Input-Output Tables, which was published most recently in April 2007 by the Bank of Korea. The korean railway service industry produced \2,766 billion worth of passenger and freight railroad services in the 2003 year, and it has induced \1,701 billion worth of output, \781 billion worth of value-added, and \580 billion worth of imports of the korean industry as a whole. The energy sector industries such as diesel fuel, thermal power generation, nuclear power generation, crude oil, liquid natural gas, bituminous coal, liquid propane gas have been most affected by the korean railway services. Other industries mainly affected by the korean railway services include railroad car manufacturing, cleaning and decontamination, medical and health service, machinery equipment and rental, construction and maintenance, transportation related services, business R&D, property insurance, and telecommunication.

• Journal of Power Electronics
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• v.10 no.2
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• pp.115-124
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• 2010

In this paper, a simple yet efficient auto mode-hop ripple control structure for buck converters with light load operation enhancement is proposed. The converter, which operates under a wide range of input and output voltages, makes use of a state-dependent hysteretic comparator. Depending on the output current, the converter automatically changes the operating mode. This improves the efficiency and reduces the output voltage ripple for a wide range of output currents for given input and output voltages. The sensitivity of the output voltage to the circuit elements is less than 14%, which is seven times lower than that for conventional converters. To assess the efficiency of the proposed converter, it is designed and implemented with commercially available components. The converter provides an output voltage in the range of 0.9V to 31V for load currents of up to 3A when the input voltage is in the range of 5V to 32V. Analytical design expressions which model the operation of the converter are also presented. This circuit can be implemented easily in a single chip with an external inductor and capacitor for both fixed and variable output voltage applications.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.11
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• pp.1996-2005
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• 2010

This paper proposes a new method for constant control of the output AC voltage of a voltage-fed three phase Z-source inverter (ZSI), in case of Z-network DC voltage variation or heavy change of load. The modulation index for the reference output AC voltage of ZSI can be calculated by the basic definition of ZSI, the input DC voltage and capacitor voltage of Z-network. And, the output AC voltage of ZSI is controlled by the modified space vector modulation (SVM) with the calculated modulation index. By the proposed method, the modulation index of output AC voltage is closely following in the reference modulation index. The validity of the proposed method is verified using PSIM simulation. In case which the input DC voltage of ZSI is heavily changed from 100[V] to 70[V] (or to 150[V]) and in case which load is changed from $30[\Omega]$ to $10[\Omega]$, we confirmed that the output AC voltage of ZSI is constantly controlled by the proposed method because the modulation index of ZSI is also simultaneously changed. Finally, FFT and %THD of the output voltage and current of ZSI by the proposed method are analyzed.

• Journal of radiological science and technology
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• v.41 no.6
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• pp.603-610
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• 2018

This study examined the following: accuracy of the exposure conditions in the inverter device and three-phase device; output waveform over the exposure conditions; and average and standard deviation of the output waveform. After assessing whether the dose corresponding to the theoretical dose was presented, the following conclusions were obtained: 1. The accuracy of the tube voltage(kVp) and tube current(mA) exposure time(sec) was within the tolerable level prescribed in Korea's Safety Management Standards. In the error, Inverter device was large the tube voltage and exposure time, the three-phase device was large the tube current. 2. In terms of the output waveform of the exposure conditions and the average and standard deviation of the output waveform, the higher tube voltage and larger tube current resulted in greater standard deviation in pulsation. Moreover, the standard deviation of pulsation was shown to be greater in the inverter device than the three-phase device; there was also greater standard deviation in the inverter device considering the exposure time. 3. Regarding the exposure conditions over the output dose, all linearity showed the coefficient of variation which had an allowable limit of error within 0.05. Although the output dose ratio for the inverter device was 1.00~1.10 times no difference that of the three-phase device, there was almost no difference in dose ratio between the tube currents.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.6
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• pp.1152-1162
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• 2011

In this paper, a single-phase DC-AC inverter using two embedded Z-source converters is proposed. The proposed inverter is composed of two embedded Z-source converters with common DC source and output AC load. The output AC voltage of the inverter is obtained by the difference of output capacitor voltages of each converter. The output voltage of each converter take shape of the asymmetrical AC waveform centering zero voltage. Therefore, the proposed inverter can generate the same output voltage despite low VA rating L-C elements, compared to the conventional inverter using high DC voltage with AC ripple. To verify the validity of the proposed system, the PSIM simulation was achieved under the condition of rapid increase of DC source (110[V]${\rightarrow}$150[V]) and R-load (50[${\Omega}$]${\rightarrow}$300[${\Omega}$]). For controlling the voltage of the inverter system, the one-cycle controller was adopted. As results, the proposed inverter output the constant AC voltage (220[V]rms/60[Hz]) for all conditions. Also, the R-L load and nonlinear diode load were adopted for the proposed inverter loads, and we could know that the its output voltage characteristics were as good as the pure R-load. Finally, the RMS and THD of output AC voltage were examined for the different loads, input DC voltages and reference voltage signals.