• International Journal of Oral Biology
• /
• v.35 no.4
• /
• pp.137-144
• /
• 2010

To evaluate the biohazard properties of an extremely low frequency electromagnetic field (ELF-EMF), we explored the physical properties of the ELF-EMF that generates the electric current induction in the secondary coil from the chamber of a primary solenoid coil. We subsequently explored the biological effects of a strong alternating electromagnetic field (EMF), ranging from 730-960 Gauss, on the mouse testis. Mice were exposed to an alternating EMF field induced by a rectangular electric current at 1, 7, 20, 40, and 80 Hertz, for 1, 3, 5, and 7 hours. The mouse testes were examined for proliferative activity and apoptosis using the in situ terminal deoxynucleotidyl transferase (TdT) method and by immunostaining of proliferating cell nuclear antigen (PCNA), respectively. We found that the electric currentm induction increased in the 6-8 Hertz range, and that exposure to an ELF-EMF induced the apoptosis of mouse spermatocytes. In situ TdT staining was found to be most prominent in 7 Hertz group, and gradually reduced in the 20, 40, and 80 Hertz groups. These data suggest that a strong EMF can induce reproductive cell death within a short time, and the harmful effects of the EMF are maximal at low frequency alternating EMFs.

• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.754-755
• /
• 2008

This paper presents a method for reducing the Total Harmonic Distortion(THD) of line-line back_EMF of the IPMSM with distributed winding under the no-load condition. Firstly, the specific harmonic components of line-line back EMF are reduced considering with winding factor. Secondly, THD of line-line back EMF is minimized according to change of pole angle using by Space harmonic Analysis. Finally, the optimal design for minimizing the THD is conducted using response surface methodology with finite element analysis. The validity of the design method dealt with in this paper is demonstrated by comparison between the THD of optimal model and initial model.

• Journal of the Korea Safety Management & Science
• /
• v.17 no.3
• /
• pp.363-370
• /
• 2015

In this paper, the control technique of the stepping motor using back electromotive force(B-EMF) without encoder is investigated. The stepping motor generally uses the rotary encoder to detect the rotor position. Since this method increases the cost and the motor configuration size, the new closed-loop control method applied for the B-EMF was implemented by using current detect circuit, AD-converter, and micro controller unit(MCU). The control loop of stepping motor became very simplified. The current change of stepping motor measured by the amplifier was measured and analyzed, when the missing step is occurred. Based on the data from current feedback, position errors were compensated and confirmed by using AD-converter.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 1997.10a
• /
• pp.32-32
• /
• 1997

• Journal of the Korean Society of Safety
• /
• v.23 no.4
• /
• pp.36-41
• /
• 2008

This report describes the analytical solution of back EMF for BLDC motor using numerical analysis of air gap flux density. The analysis of air gap flux density is the key to expect the performance of back EMF for the design of brushless motor. The numerical analysis and FEM analysis are performed to vary attachment of stator side or rotor side, radial flux magnetization or parallel flux magnetization, magnet arc angle in the condition of constant air gap. This results have more reliable data comparing with test result of the back EMF for 7 phase BLDC motor.

• Proceedings of the KIPE Conference
• /
• 2007.11a
• /
• pp.7-10
• /
• 2007

The current model based sensorless method has many benefits that it can be robust control for large load torque. However, this method should determine a coefficient of back electro motive force(back-emf). This coefficient is varied by load torque and speed. Also, the coefficient determining equation is not exist, so it is determined only by experiment. On the other hands, using only back-emf estimatior method can not drive in low speed area and it has weakness in load variation. For these problems, this paper suggests the hybrid sensorless method that mixes the back-emf estimator regarding saliency and the current based sensorless model. This estimator offers not only non-necessary coefficient for current sensorless model, but also wide speed area operating in no specific transition method.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.2B no.4
• /
• pp.162-167
• /
• 2002

This paper presents the dynamic analysis method for a slotless permanent magnet linear synchronous motor (PMLSM) using the 3-D space harmonic method. Instantaneous emf and thrust are considered by movement of the PM and instantaneous armature current instead of $K_E$ (back-emf constant) and $K_F$(thrust force constant) for accurate results. The results of magnetic field distribution, back-emf, inductance, and thrust are in agreement with 2-D FEM and experimental results. To confirm the validity of this method, the calculated results are compared to measured ones.

• Analytical Science and Technology
• /
• v.10 no.4
• /
• pp.300-306
• /
• 1997

The effective resolution of the direct current potential drop (DCPD) method for crack length determination is strongly affected by a number of factors including wire locations and calibration method. In the present study, the effects of wire locations, thermal EMF and reference probe locations on the accuracy of calibration methods, including Hicks-Pickard equation and Johnson's equation, were examined with the CT specimens which were nine times larger than the standard specimen. In light of experimental results, it was found that Hicks-Pickard equation can accurately represent the a/W-V/Vo relationship when current input wire is located at the load line. It was also found that the accuracy of DCPD method can be greatly improved with the thermal EMF calibration and the use of Vo value at a/W = 0.241. The use of reference potential was found to be impractical when current input wire is located at the load line.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.8 no.1
• /
• pp.56-63
• /
• 2003

This paper studies that torque model considered with decaying phase back-EMF is different In conduction and commutation period and analyzes the torque pulsation components mathematically. In this paper, it is proposed a novel method to suppress torque pulsation due to commutation time. First, it propose commutation delay time control method, which is to compensate current slope of rising phase and decaying phase to control commutation time. Current ripple is minimized at non-commutating current and torque ripple is reduced below critical speed range that dc link voltage is the same as four times of back-EMF voltage. However, torque ripple still exists due to the relation with back-EMF and commutating current and it is increased on a large scale above critical speed range, especially. Secondly, proposed method is commutation time control, which is considered with torque pulsation due to the relation of back-EMF and commutating current. Through the proposed method, the torque pulsation can be minimized in the whole speed range as well as range over critical speed.

• Journal of Power Electronics
• /
• v.16 no.1
• /
• pp.1-8
• /
• 2016

Dead time is typically incorporated in voltage source inverter systems to prevent short circuit cases. However, dead time causes an error between the output voltage and reference voltage. Hence, voltage equation-based algorithms, such as motor parameter estimation and back electromotive force (EMF)-based sensorless algorithms, are prone to estimation errors. Several dead-time compensation methods have been developed to reduce output voltage errors. However, voltage errors are still common in zero current crossing areas, and an effect of the error is much worse in a low speed region. Therefore, employing voltage equation-based algorithms in low speed regions is difficult. This study analyzes the conventional dead-time compensation method and output voltage errors in low speed operation areas. A current shaping method that can reduce output voltage errors is also proposed. Experimental results prove that the proposed method reduces voltage errors and improves the accuracy of the parameter estimation method and the performance of the back EMF-based sensorless algorithm.