• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.1
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• pp.84-90
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• 2012

Various methods have been proposed to identify the flux position in an interior permanent magnet synchronous motor (IPMSM) without the use of mechanical sensors. To achieve this, a method that uses both the back electromotive force (EMF) and the saliency to identify the flux position in the IPMSM without the injection of high-frequency components at low speeds has been reported. This method was then extended in order to drive the motor with no load to a light load. We propose a combination of these methods with different proportional-integral (PI) controllers for controlling $di_{dest}$/dt and $di_{qest}$/dt. We also introduce compensation values $F_L$ and $F_H$ to reduce the position error when the estimation rule is being selected.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.2
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• pp.134-140
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• 2013

This paper proposes a new design of rotor shape of Interior Permanent Magnet Synchronous Motor (IPMSM) used for agricultural electric vehicle (AEV). The distribution of the residual magnetic flux density at the air gap is modified by rotor surface shape and V-type magnet angle. As a result, cogging torque and physical characteristic have been improved, and back electromotive force (back-EMF) of the suggested model has been improved to be closest to sine wave form compared to initial model. The validity of the proposed rotor shape optimization is confirmed by the manufactured IPM rotor core and measured the performance of the cogging torque.

• Journal of Magnetics
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• v.22 no.1
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• pp.122-132
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• 2017

This study dealt with the design process of the 78 kW permanent magnet synchronous generator for engines. After the calculation of the basic dimensions through a theoretical method in the process of initial model design, FEA (finite-element analysis) and a d,q-axis equivalent circuit were used to identify the generator characteristics depending on the number of poles. With the use of the space harmonic analysis method, the back-EMF (electromotive force) and THD were checked, and then the number of slots was determined. In addition, the most optimized generator dimensions were determined through a sizing optimization technique. Based on this, the optimum model with enhanced efficiency, material costs, and temperature characteristics was derived, and the availability of the design method was confirmed through a comparative analysis of the initial and optimum models.

• Journal of Electrical Engineering and Technology
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• v.12 no.3
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• pp.1166-1176
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• 2017

Estimation errors of the rotor speed and position in sensorless control systems of Permanent Magnet Synchronous Motors (PMSM) will lead to low efficiency and dynamic-performance degradation. In this paper, a parallel-type extended nonlinear observer incorporating the nominal parameters is constructed in the stator-fixed reference frame, with rotor position, speed, and the load torque simultaneously estimated. The stability of the extended nonlinear observer is analyzed using the indirect Lyapunov's method, and observer gains are selected according to the transfer functions of the speed and position estimators. Taking into account the parameter inaccuracies issue, explicit estimation error equations are derived based on the error dynamics of the closed-loop sensorless control system. An equivalent flux error is defined to represent the back Electromotive Force (EMF) error caused by the inaccurate motor parameters, and a compensation strategy is designed to suppress the estimation errors. The effectiveness of the proposed method has been validated through simulation and experimental results.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.6
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• pp.543-546
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• 2017

This paper presents a simple approach for improving the performance of back-electromotive force (back-EMF)-estimation-based sensorless drives for surface-mounted permanent magnet synchronous motors (SPMSM). Similar to conventional approaches, a hypothetical d-q synchronous reference frame model of SPMSM is employed in the proposed approach to estimate the back-EMFs. This approach also employs a dual phase locked loop structure to compensate for the effect of the dead time and parameter uncertainty of the inverter on the estimated back-EMFs. The proposed algorithm is validated by conducting experiments.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.3
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• pp.275-282
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• 2012

This paper presents a comparison of antenna factor characteristics computed by the Method of Moments(MoM) and the electromotive force(EMF) method for a calculable dipole antenna with a hybrid balun. An expression for the antenna factor is formulated using the concept of power mismatch loss. The input impedance and effective length of the antenna, which are in the formula of the antenna factor, are calculated using the two methods. The results show that the antenna factors are agreed within 0.24 dB, although the maximum difference between the input impedances obtained from the two methods is about 17 ${\Omega}$.

• Journal of the Korean Chemical Society
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• v.18 no.5
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• pp.320-328
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• 1974

It is unable to derive the standard emf ($E^{\circ}$) of the cell at high pressure from the conventional method. However, when the concept of the complete equilibrium constant($K{\circ})$) is available to the conventional Nernst equation, it is possible to get the standard emf of the cell at high pressure(complete Nernst equation). Moreover, the other thermodynamic properties, such as the net change of solvation number(k), the compressibility of solvent(${\beta}$), ionization constant(K), the standard free energy change(${\Delta}G^{\circ}$), the standard enthalpy change(${\Delta}H^{\circ}$) and the standard entropy change (${\Delta}S^{\circ}$) of the cell reaction at equilibrium state have been also obtained. In this experiment, the emf of the cell; 12.5 % Cd(Hg)│$CdSO_4(3.105{\times}10^{-3}M),\;Hg_2SO_4│Hg$ have bee measured at temperature from 20 to $35^{\circ}C$ and at pressures from 1 to 2500 atms. The emf of the cell increased with increasing pressure at constant temperature, and did with increasing temperature at constant pressure. The net change of solvation number(k) of the cell reaction was 41.96 at $25^{\circ}C$, and kept constant value with pressure, while, K and ${\Delta}S^{\circ}$ increased with pressure, but whereas ${\Delta}G^{\circ}$ and ${\Delta}H^{\circ}$ decreased. Since the standard emf of the cell at high pressure can be calculated from the complete Nernst equation, the theory of chemical equilibrium could be developed with at high pressure as well as at the atmosphere.

• Journal of the Korean Chemical Society
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• v.37 no.7
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• pp.635-641
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• 1993

Electrochemical cell, $Pt|air(PO_2=5.3{\times}10^{-3}atm)|Zr_{0.85}Ca_{0.15}O_{1.85}|air(PO_2= 0.21atm)|Pt$, has been designed to characterize the solid electrolyte and the temperature dependence of the electromotive force (EMF) has been measured in a temperature range of 600∼1000${\circ}$C. Solid electrolyte shows pure ionic conduction of the oxygen anion. The Fe-FexO, Co-CoO, Ni-NiO, and Cu2O-CuO electrodes have been prepared by mixing the 1 : 1 mole ratio of each metal and metal oxide and then by heating at 800${\circ}$C for 6 hours. Electrochemical cells, Pt│M(s), $MO(s)|Zr_{0.85}Ca_{0.15}O_{1.85}|air(PO_2=0.21atm)|Pt$, have been designed and the temperature dependence of the EMF has also been measured in the same temperature range. The changes of the thermodynamic state functions for the formation of the metal oxides are calculated from the electromotive forces and their temperature dependences. The material properties of the oxide systems are also discussed with the function changes.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.840-842
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• 2001

The cogging torque and torque ripple in motor which cause noise and vibration are an inevitable phenomenon and they give a bad effect to motor performance. So we are required to reduce the cogging torque and torque ripple not by electrical controlling but by changing the inner mechanical structure and we focused on the permanent magnet. In this research, we calculated current, torque, Back-EMF(electromotive force) and cogging torque according to the change of the magnet shape using two dimensional FEM(Finite Element Method). Maxwell stress tensor and time-stepping method. From the results, we present an appropriate model that can satisfy both low cogging torque, low torque ripple and high efficiency.

• Journal of Power Electronics
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• v.17 no.1
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• pp.96-105
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• 2017

In this paper, a hybrid modular multilevel converter (MMC) topology with an improved nearest level modulation method is proposed for medium-voltage high-power applications. The arm of the proposed topology contains N series connected half-bridge submodules (HBSMs), one full-bridge submodule (FBSM) and an inductor. By exploiting the FBSM, half-level voltages are obtained in the arm voltages. Therefore, an output voltage with a 2N+1 level number can be generated. Moreover, the total level number of the inserted submodules (SMs) is a constant. Thus, there is no pulse voltage across the arm inductors, and the SM capacitor voltage is rated. With the proposed voltage balancing method, the capacitor voltage of the HBSM is twice the voltage of the FBSM, and each IGBT of the FBSM has a relatively low switching frequency and an equalized conduction loss. The capacitor voltage balancing methods of the two kinds of SMs are implemented independently. As a result, the switching frequency of the HBSM is not increased compared to the conventional MMC. In addition, according to a theoretical calculation of the total harmonic distortion of the electromotive force (EMF), the voltage quality with the presented method can be significantly enhanced when the SM number is relatively small. Simulation and experimental results obtained with a MMC-based inverter verify the validity of the developed method.