• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.3
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• pp.292-298
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• 2003

Most of the three phase inverters for adjustable speed drive of AC machines are equipped with two or three current sensors for measurement of three phase current. One method to reduce the number of current sensors is that single current sensor measures the DC link current, then three phase current is reconstructed using the measured value and the switching status. To improve the measurement accuracy, switching state should be maintained for more than minimum switching time. Many papers have been published, which focused on the readjustment of pulse width and compensation of voltage distortion. Those methods are suitable for space vector modulation. But there are some difficulties in applying these methods to carrier-based PWM which is widely used in industry. In this paper, new current measurement method and voltage compensation method are proposed which are suitable for carrier-based PWM, then, the validity of proposed method is confirmed through experiment.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.10
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• pp.1465-1469
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• 2013

The resent developed high speed train called HEMU-430X (Highspeed Electric Multiple Unit - 430km/h eXperiment) recorded a 421.4 km/h in Kyoungbu high speed line in Korea. A verity of measurement systems are used to check the performance between pantograph and catenary system. An innovative measurement system is adopted to check the current of catenary wire in the track side during HEMU-430X test running. This paper presents the measurement results of catenary current in kyoungbu high-speed line and describe its utilizing technology in the experimental results of catenary current. In order to analyze field testing results, the current ratio between contact and catenary current have been analyzed by means of Carson-Pollaczek equation. And the current wave forms between catenary and contact wire are presented based on the simulation results.

• Journal of Power Electronics
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• v.10 no.3
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• pp.313-319
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• 2010

This paper proposes a new compensation algorithm for the current measurement errors in a DFIG (Doubly Fed Induction Generator). Generally, current measurement path with current sensors and analog devices has non-ideal factors like offset and scaling errors. As a result, the dq-axis currents of the synchronous reference frame have one and two times ripple components of the slip frequency. In this paper, the main concept of the proposed algorithm is implemented by integrating the 3-phase rotor currents into the stationary reference frame to compensate for the measured current ripples in a DFIG. The proposed algorithm has several beneficial features: easy implementation, less computation time, and robustness with regard to variations in the electrical parameters. The effectiveness of the proposed algorithm is verified by several experiments.

• Journal of Ocean Engineering and Technology
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• v.35 no.2
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• pp.150-160
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• 2021

To ensure the international competitiveness of the domestic offshore plant industry, a consensus has been formed regarding the requirement for large offshore basins for performing offshore plant performance verification. Accordingly, the Korea Research Institute of Ships & Ocean Engineering has built the world's largest deep ocean engineering basin (DOEB). The purpose of this study is to evaluate the characteristics of velocity distribution under various conditions of the DOEB. An independent measuring jig is designed and manufactured to measure the current velocities of many locations within a short time. The measurement jig is a 15-m-high triangular-truss structure, and the measurement sensors can move 15 m vertically through an electric motor-wire device. The current speed is measured under various impeller revolutions per minute and locations of the DOEB using the jig. The spatial distribution characteristics of the current velocity in the DOEB and the performance of the current generator are analyzed. The maximum speed is 0.56 m/s in the center of the DOEB water surface, thereby confirming sufficient current velocity distribution uniformity for model testing.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.06a
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• pp.424-425
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• 2022

This paper introduces X-band radar-based surface current measurement technique. A marine X-band radar used for navigation was installed at Sokcho Beach to collect surface current data in real time. Based on this, in order to verify the accuracy of the measurement of surface current (Current speed), the Korea Hydrographic and Oceanographic Agency Marine observation buoy compared it with the data. Data collected from January 2022 were compared and as a result the possibility of surface current(Current speed) measurement using radar confirmed.

• Progress in Superconductivity and Cryogenics
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• v.22 no.4
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• pp.62-66
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• 2020

We fabricated superconducting quantum interference devices (SQUIDs) based on Nb Josephson junctions, and characterized the key parameters of the SQUIDs. The SQUIDs are double relaxation oscillation SQUIDs (DROSs) having larger flux-to-voltage transfer coefficient than the standard DC-SQUIDs. SQUID sensors were fabricated by using Nb junction technology consisted of a DC magnetron sputtering and a conventional photolithography process. In multichannel SQUID systems for whole-head magnetoencephalography measurement with a helmet-type SQUID array, we need about 336 SQUID sensors for each system. In this paper, we fabricated a few hundred SQUID sensors, measured the critical current, flux modulation voltage and decided if each tested SQUID can be used for the multichannel systems. As the criterion for the acceptance of the sensors, we chose the critical current and amplitude of the modulation voltage to be 8 ㎂ and 80 ㎶, respectively. The average critical current of the SQUIDs was 10.58 ㎂. The typical flux noise of the SQUIDs with input coil shorted was 2 μΦ0/√Hz at white region.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.12
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• pp.1045-1053
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• 2002

This paper describes characteristics of the developed current sensor by means of two identically wound magnetic cores forming a clamp like for measurement of a low DC, or AC current. This sensor consists of peak value detectors, a sensor of an electrically compensated current transformer type, a reference alternating voltage, Precision measuring circuits to measure the output signals of sensor with harmonics, and can be measured up to 2 A at DC, or AC current. The current sensor shows a measurement accuracy of less than 0.3% in the frequency range 40 Hz - 10 HBz. The resolution and sensitivity of the sensor were evaluated 0.1 mA and 10 mV/mA, respectively.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.3
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• pp.162-170
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• 2020

In this paper, we report our study of the current measuring technique by implementing a pick-up coil in the PCB pattern instead of the current measuring sensor in a power converter using a WBG device. The proposed PCB pattern coil structure has a higher mutual inductance value than the conventional pattern by constructing the coil using the multi layer board. It has high sensitivity and is configured without additional process outside the PCB. In the current measurement, the integrator is measured by integrating the coil at the back end and the current waveform measured using proposed pick-up coil is confirmed by comparing it with the original current waveform through DPT simulation.

• Journal of Magnetics
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• v.21 no.4
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• pp.524-528
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• 2016

Eddy current (EC) sensor works based on the electromagnetic induction principle and has been widely applied in the industrial testing and evaluation due to its robustness and environmental adaptability. Meanwhile, tilt angle measurement is mainly based on the laser or visual method, which is strict with the measurement environment and not suitable for the industrial applications. In this paper, a novel tilt angle measurement method based on arrayed EC sensors is proposed. Both the simulation and experiments indicate that the measured error is approximately linear with tilt angle and the accuracy after compensation is $0.25^{\circ}$. In conclusion, this research cannot only broaden the scope of EC application, but also overcome the shortcomings of existing angle measurement methods.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.532-540
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• 2014

It is necessary to measure the current of rotor for controlling the active and reactive power generated by the stator side of the doubly fed induction generator (DFIG) system. There are offset and scaling errors in the current measurement. The offset and scaling errors cause one and two times current ripples of slip frequency in the synchronous reference frame of vector control, respectively. This paper proposes a compensation method to reduce their ripples. The stator current is variable according to the wind force but the rotor current is almost constant. Therefore input of the rotor current is more useful for a compensation method. The proposed method adopts the synchronous d-axis current of the rotor as the input signal for compensation. The ripples of the measurement errors can be calculated by integrating the synchronous d-axis stator current. The calculated errors are added to the reference current of rotor as input of the current regulator, then the ripples are reduced. Experimental results show the effectiveness of the proposed method.