• Journal of the Korean Society for Precision Engineering
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• v.17 no.12
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• pp.61-67
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• 2000

In switched reluctance motor(SRM) drive, it is necessary to synchronize the stator phase excitation with the rotor position. Therefore the rotor position information is an essential. Usually optical encoders or resolvers are used to provide the rotor position information. These sensors are expensive and are not suitable for high speed operation. In general, the accuracy of the switching angle is dependent upon the resolution of the encoder and the sampling period of the microprocessor. But the region of high speed, switching angles are fluctuated back and forth from the preset values, which are cause by the sampling period of the microprocessor. Therefore, the low cost linear encoder suitable for the practical and stable SRM drive is proposed and the control algorithm to provide the switching signals using the simple digital logic circuit is also presented in this paper. It is verified from the experiments that the proposed encoder and logic controller can be a powerful candidate for the practical low cost SRM drive.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.12
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• pp.874-887
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• 1987

The efficiency of a synchronous motor can be substantially improved by controlling armature voltage, field excitation, and load angle on optimum values which yield minimum input power at any specified torque and speed. This improvement is particularly noticeable in the case of light loads. In addition, the control of armature input voltage improves the power factor at which the motor operates. Employed in the analysis is a new equivalent circuit model of the motor which incorporates the frequency dependent nature of the motor parameters and the effects of iron loss. The stability of synchronous motor operation is studied by applying the Nyquist stability criterion to the linearized equations which describe the behavior of the motor as the motor loads perturb about a steady-state operating point. This investigation reveals that, in some cases, the stable region of the motor is delineated from the results of a computer simulation. With a view to reducing harmonic loss and improving torque pulsation from harmonic components, a very poweful pulse amplitude modulation (PAM) method using an 16-bit microcomputer has been developed. This method has the advantages of simplicity of control algorithms and requires small memory space for storing thyristor trigger angles for a three-phase PAM inverter. The method can be used for smooth control of both modulation depth and frequency over a wide range.

• Journal of IKEEE
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• v.2 no.2 s.3
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• pp.166-172
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• 1998

Switched reluctance motor(SRM) has the advantages of simple structure, low rotor inertia and high efficiency. However, position sensor is essential in SRM in order to synchronize the phase excitation to the rotor Position. The Position sensors increase the cost of drive system and tend to reduce system reliability. This paper investigates the speed control of sensorless SRM in which the Phase current and change rate are utilized in position decision, and the period of dwell angle is variable for speed control. The proposed system consists of Position decision circuit, speed controller, digital logic commutator, switching angle controller and inverter The performances in the proposed system are verified through the experiment.

• Journal of information and communication convergence engineering
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• v.14 no.4
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• pp.252-257
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• 2016

An edge-located electromagnetic bandgap (EL-EBG) structure using a defected ground structure (DGS) is proposed to suppress resonant modes induced by edge excitation in a two-dimensional planar parallel plate waveguide (PPW). The proposed EL-DGS-EBG PPW significantly mitigates multiple transverse-magnetic (TM) modes in a wideband frequency range corresponding to an EBG stopband. To verify the wideband suppression, test vehicles of a conventional PPW, a PPW with a mushroom-type EBG structure, and an EL-DGS-EBG PPW are fabricated using a commercial process involving printed circuit boards (PCBs). Measurements of the input impedances show that multiple resonant modes of the previous PPWs are significantly excited through an input port located at a PPW edge. In contrast, resonant modes in the EL-DGS-EBG PPW are substantially suppressed over the frequency range of 0.5 GHz to 2 GHz. In addition, we have experimentally demonstrated that the EL-DGS-EBG PPW reduces the radiated emission from -24 dB to -44 dB as compared to the conventional PPW.

• Journal of Sensor Science and Technology
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• v.23 no.3
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• pp.202-206
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• 2014

The common vibration energy harvester effectively converts mechanical vibration to electric power at a specific resonance frequency that must match the ambient excitation frequency. The resonance frequencies of energy harvesters are fixed during the design process and could not be changed after fabrication. In this paper, we proposed the new frequency tuning which uses the rotatable spring in order to adjust the spring constants. By this tuning method, the resonance frequency of the system can simply be manipulated using spring rotation. The proposed energy harvester has been successfully tuned to a resonance frequency between 23 and 32 Hz. The experimental results demonstrated that the proposed energy harvester could generate a maximum output power of $60{\mu}W$ with an acceleration of 0.5 g ($1g=9.81m/s^2$), and that the resonance frequency of the harvester was able to tune approximately 31.4%. When the proposed harvester was attached to an automobile engine, the maximum open circuit voltage of 1.78 Vpp was produced at 700 rpm.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1029-1033
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• 2006

During operation of generator, the excitation force with 120Hz always exist irrespective of No. of poles. Therefore the vibration is generated in the stator end windings and the micro-crack is grown up inside the bars. After all, coolant water is leaked outside the bars or the stator is moved and is worn out. What is more, one bar is touched with another bar so a short circuit may frequently happen in operation. In order to prevent it from occurring, the evaluation of mechanical integrity for generator stator windings is carried out periodically during overhaul period. This help troublesome end windings to complement with insulation material and to change vibration characteristics. In this paper, the evaluation of mechanical integrity for generator stator windings is described and the change of vibration characteristics is analysed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.8
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• pp.823-829
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• 2003

For high frequency microstrip line modelling, a fast inductance extraction technique using an adaptive PEEC(partial element equivalent circuit) grid is proposed. The grid refinement technique is based on the current distribution depend on the excitation frequencies and the geometry of the microstrip lines. The adaptive ids are refined mainly in the area where heavy currents reside. This technique is applied to the inductance extraction of the microstrip lines. The results show fast convergence, and this adaptive technique is efficient to reduce computing time and the number of grids.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.3
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• pp.107-114
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• 2001

Electro-mechanical battery (EMB) consists of a high-speed fly wheel with an integral motor/ generator suspended on magnetic bearings and in an evacuated housing. Permanent magnet (PM) machines as the EMB motor/ generator are a popular choice, since there are no excitation losses which means substantial increase in the efficiency. In this paper we present the comparison of conventional slotted and slotless ring-wound types, aimed at EMB and other high-speed drives. We firstly discuss the topology of each machine for this particular application. these machines are primarily designed as 1kW two-pole PM generator with the rated speed of 40000 rpm. the motoring torque of 0.51 Nm has to be enough to accelerate the flywheel to the rated speed. We then present the comparison of the open-circuit field, the armature reaction field and winding inductance. next we analyze the induced voltage and the developed torque per unit stack length and unit weight of different machines. Finally, we estimate and compare the losses and the efficiency at motoring and generating modes.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.637-638
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• 2006

Different from the conventional motor, the superconducting motor has so large air-gap that the actual parameters such as excitation voltage have considerable difference from the values obtained from 2-dimensional electromagnetic analysis. This paper introduces 3-dimensional EMCH(Equivalent Magnetic Circuit Network) method or FLUX-3D FEM(Finite Element Method) software to reduce the error originated from the 2-dimensional electromagnetic analysis for the development of a 1 MW class high-temperature superconducting motor.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.12
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• pp.8-15
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• 2007

This paper presents the radiation rate formula due of a inclusion of a series capacitor and shunt inductor in a unit cell for the right/left-handed transmission line (RLH-TL). The equivalent circuit for a RLH unit cell considering radiation effects is presented and analyzed in terms of the Bloch impedance and dispersion diagram. It has been found that when two radiation rates are identical, the Blockimpedance reduces to the characteristic impedance of the host conventional RH-TL. Besides, design equations for a unit cell for a specific phase shift at a given frequency are provided. The method of realizing uniform excitation along the RLH-TL is also proposed for antenna applications.