• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.10-12
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• 1997

For a given brushless DC linear motor, we analyze the thrust characteristics. We measure the back-EMF and then calculate the thrust with it. To compare the thrust, we measure it direct with force-torque meter and we calculate it from Lorentz equation. As the thrust and the back-EMF vary linearly according to the current and the velocity respectively, we define the thrust constant and the back-EMF constant. To match the motor to its controller, we calculate the thrust constant and the back-EMF constant. The result calculated with the back-EMF differs from that of the measurement by only 4.4%.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.5
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• pp.525-533
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• 2013

As the number of base stations for mobile communication services rapidly grows with the development of mobile communications and the increase of radio-use devices, there are hazardous concerns raised on the possible health effects of EMF(Electro-magnetic fields) radiated from base station antennas. Since 2007, KCA(Korea Communications Agency) has been measuring the EMF on base station defined by Radio Act. This paper was studied to provide objective and accurate information that relieved anxiety of people by analyzing the measurement results on EMF strength. Also, we suggest to effectiveness and improvement of EMF measurement institution by analyzing measurement results since it was introduced on June 2007.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.12
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• pp.942-952
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• 2018

A wireless power transfer (WPT) system for an urban railroad is currently under development in S. Korea. This system supplies power to railroad cars using 60 kHz magnetic fields. The electromagnetic fields (EMFs) generated by the WPT system should satisfy established safety requirements for exposure of the human body to these fields. However, EMF measurements and the safety assessment methods for fields generated by the WPT system have not yet been established. As such, a measurement and safety assessment method for EMF generated by a WPT system for an urban railroad is proposed in this report. The EMF generated by this WPT system on a test railroad was measured and compared to the reference level set by the human safety standard for EMF exposure.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.8
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• pp.183-192
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• 1998

In this paper, we measure the back-EMF and the thrust of a linear brushless DC motor along the relative position between coils and magnets in various speed environments in order to obtain the back-EMF and the thrust as a function of a motor position. The measured back-EMF function and thrust function of the position differ from the analytical ones within 5%. The measured back-EMF and thrust function can, then, be employed in controlling the thrust ripple of the linear motor. Furthermore, to minimize the torque ripple of the linear motor, we suggest the design method to shape the back-EMF and thrust function of the linear motor.

• Transactions of Materials Processing
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• v.19 no.1
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• pp.38-43
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• 2010

Electromagnetic forming (EMF) method is one of high-velocity forming processes, which uses electromagnetic Lorentz force. Advantages of this forming technique are summarized as improvement of formability, reduction in wrinkling, non-contact forming and applications of various forming process. In this study, the EMF apparatus is developed. It is designed to be stored in 10 capacitors connected in parallel, each with a capacitance of $50{\mu}F$ and maximum working voltage of 5kV. The system has capacitance of $500{\mu}F$ and maximum stored energy of 6.25kJ. And EMF experiments are carried out to verify the feasibility of the EMF apparatus, which has enough forming force from the results of EMF experiment. In addition, peak current carrying a forming coil is predicted from theoretical background, and verified the predicted value compared with experimental value using the current measurement equipment. Consequently, EMF apparatus developed in this study can be applied to various EMF researches for commercialization.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.6
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• pp.601-609
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• 2010

This paper measured EMF strength of the duty measurement radio station(77 station) and the non-duty measurement radio station(41 station) of mobile communication base station in Jeonbuk region. As the result of measurement, it generally reveals that EMF is highly low level compare to the human protection guideline. And It is regarded as level that the national people who live close to the mobile communication base station don't have to worry about electromagnetic wave. This paper provides comparative analyses categorized by the duty measurement station and the non-duty measurement station. The results reveals that the average value and the maximum value of the non-duty measurement station preferably was higher than all the duty measurement station. It is thought that the EMF exposure strength of the national people is caused by approach of station antenna rather than antenna power. Consequently this paper suggests that standard of the antenna power(exceed 30 W), standard of antenna height(exceed 10 m) specified by Radio Regulation Act enforcement ordinance, legal basis for mobile communication base station have to be changed.

• Journal of Science and Technology Studies
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• v.19 no.3
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• pp.119-166
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• 2019

The risk of electromagnetic field(EMF) from power lines has been heavily disputed whenever high-voltage power line towers were built in South Korea. Local communities and civic groups had regarded burying the lines in the ground as an alternative to building power line towers. In 2014, however, when an elementary school science teacher reported the results of EMF measurements over the underground power lines to the Asian Citizens' Center for Environment and Health (ACCEH), the risk controversy over underground power lines took a whole new turn. The level of EMF from underground power lines turned out to be higher, and therefore more harmful than that from power line towers. In the debates that took place from then on over the EMF risk, ACCEH and NIER(National Institute of Environmental Research) presented conflicting topographies of EMF risk. This paper examines measuring practices of ACCEH and NIER by analyzing the measuring sites, measuring devices, and measuring heights chosen by each organization. This paper further examines how ACCEH and NIER mobilized various standards(EMF exposure limit, measurement guideline, categorization of carcinogens) differently. This controversy on the EMF from underground power lines of Seoul has raised concerns on the non-thermal effects of EMF in the long-term exposure and has led people to question whether burying the power lines is the safe alternative to building power line towers. Furthermore, this suggests conflicting answers on whether Seoul, where 90 % of transmission lines were already buried, is a safely managed place or not.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.10
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• pp.1385-1392
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• 2003

An electromagnetic flowmeter(EMF) was developed and its characteristics were compared with a commercial EMF. The developed EMF was designed as the 100 mm nominal diameter. A signal processing circuit was also developed for generating the magnetic field and converting the flow signal to flowrate and flow quantity. In order to obtain a more stable and reliable flow signal, the double magnetizing frequency was adopted for magnetizing the coil of the EMF. For the characterization of the developed EMF, the uncertainty of calibrator was estimated within $\pm$0.5 %. The evaluation procedure of the uncertainty followed the ISO Guide to the Expression of Uncertainty in Measurement. It was found that the flow signals between the electrodes were about $\pm$60-$\pm$300$\mu$V, which were sufficient for the discrimination of flowmeter and the protection of noise. The test results against the calibrator showed the good linearity in the range of 3 ㎥/h and 70 ㎥/h. A commercialized design of the EMF based on the current study will be technically more competitive in domestic and foreign market.

• Journal of Power Electronics
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• v.3 no.1
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• pp.55-61
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• 2003

This paper presents parameter measurement for permanent magnet synchronous motors based on the P-Q circle diagram. Three electrical parameters of permanent magnet synchronous motors, i.e., the equivalent iron loss resistance, armature inductance, and electrical motive force (emf) coefficient are simultaneously measured. The advantages of this method are that it can be implemented under constant excitation and it dispenses with the generating test for the emf coefficient. The proposed method is applied to a 160w permanent magnet synchronous motor, and then the measurement results are analyzed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.1
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• pp.132-140
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• 2009

For human exposure assessment of UHF RFID system, electric field distribution of commercial 900[MHz] RFID antenna was measured and analyzed. Also, SAR(Specific Absorption Rate) of RFID antenna was calculated by simulation, and compared with basic restrictions in EMF guidelines. For EMF exposure assessment according to EN and IEC standards, the reader was tested for the normal operation, and electric field from RFID antenna was measured at various distances and angles. For electric field measurement, narrow band isotropic electric field probe was used, and the measurements were made at 0.3, 0.5, 1.0 and 1.5[m] for every 15[$^{\circ}$] angle from the antenna. Also, the rationale for measurement distance in EN and IEC standards is analyzed from the measurement results.