Seong-Hwa Kang

Comparison of Classification Rate for PD Sources using Different Classification Schemes

Insulation failure in an electrical utility depends on the continuous stress imposed upon it. Monitoring of the insulation condition is a significant issue for safe operation of the electrical power system. In this paper, comparison of recognition rate variable classification scheme of PD (partial discharge) sources that occur within an electrical utility are studied. To acquire PD data, five defective models are made, that is, air discharge, void discharge and three types of treeinging discharge. Furthermore, these statistical distributions are applied to classify PD sources as the input data for the classification tools. ANFIS shows the highest rate, the value of which is 99% and PCA-LDA and ANFIS are superior to BP in regards to other matters.

Characteristics of Disk-type Linear Ultrasonic Motor for Application to x-y Stage

In this paper, a disk-type ultrasonic motor using a combination of radial and bending vibration modes is newly designed and fabricated. The characteristics of the test motor are also measured. By means of traveling elastic wave induced at the surface of circumference of the elastic disk, a steel bar in contact with the surface of circumference of the elastic disk bonded onto the piezoelectric ceramic disks is driven in both directions by changing the sine and cosine voltage inputs. The stator of the motor is composed of two sheets of piezoelectric ceramic disks to bond onto both surfaces of an elastic disk, respectively. As a result, the diameter of the elastic body is increased and the resonant frequency is decreased. The resonant frequency of the stator is about 92 ㎑, which is composed with piezoelectric ceramic disks of 28 ㎜ in diameter and 2 ㎜ in thickness, and an elastic body of 32 ㎜ in diameter and 2 ㎜ in thickness. A driving voltage of 20 Vpp produces 200 rpm with a torque of 1 Nm and an efficiency of about 10 %.

Classification of defects and evaluation of electrical tree degradation in cable insulation using pattern recognition method and weibull process of partial discharge

The purpose of this paper is to recognize partial discharge (PD) sources and evaluate of electrical treeing degradation for cable insulation. To acquire PD data, three defective tree models were made. And the data are shown by the phase-resolved partial discharge method (PRPD). As a result of PRPD, tree discharge sources have their own characteristics. If other defects (void, metal particle) exist at internal power cable, their characteristics are shown very differently. This result is related to the time of breakdown and this is important point of cable diagnosis. To apply PD data classification, methods of different type are selected. Those are, multi layer perceptions (MLP-BP), adaptive neuro-fuzzy inference system (ANFIS) and principle component analysis-linear inference system(PCA-LDA). As a result, ANFIS shows the highest rate which value is 100 %. Finally, we performed classification of tree progress using ANFIS and that result is 99 %. To evaluate degradation of electrical tree, weibull distribution was used. The time of each degradation stage (initiation, middle, breakdown) was measured to classify electrical tree degradation with each model by. Using the result, parameters are presumed by the each model and stage and it is possible to calculate time difference of each degradation stage and estimate the lifetime.

Characteristics of π-shaped Ultrasonic Motor

In this paper, the design and characteristics of a Π-shaped ultrasonic motor that is applicable to optical zoom operation of a lens system for mobile phones are investigated. Its design and simulation of performances are carried out by FEM (finite element method) commercial software. As a simulation result, by applying voltage with single phase, a combined vibration is produced at the surface of a stator arm. A prototype of the motor is fabricated and its outer size is 8*4*2 ㎣ including the cylindrical steel rod of 2 ㎜ in diameter as the rotor. The motor exhibits a maximum speed of 500 rpm and a power consumption of 0.3 W when driven at 20 Vpp and 64 ㎑.

Correlation between partial discharges and electrical treeing in low density polyethylene blended with organic additives

It is well known that there is a close relationship between electrical treeing and internal partial discharge. The purpose of the study is to characterize electrical treeing of insulators by analyzing the partial discharge characteristics. We carried out measurements of the electrical treeing characteristics, such as shape, length, and area of tree with voltage application time, and of the partial discharge characteristics, such as discharge magnitudes and number of discharge pulses in the sample, simultaneously. From the experimental results, we confirmed the following; 1) the shapes of trees are quite different depending on PD characteristics, that is, bush type were grown in the samples in which the magnitude and repetition rate of discharge were observed to be larger than those of branch type treed samples. 2) the magnitude of PD shows a good linear relation with the area of tree rather than the length of tree in the case of bush-like tree.<<ETX>>

The Design and Characterization of Ultrasonic Motor for Optical Zooming of Camera in Mobile Phones

In this paper, the design and characteristics of a p-shaped ultrasonic motor which is applicable to optical zoom operation of lens system for mobile phone are investigated. Its design and simulation of performances are carried out by FEM (finite element method) commercial software. As a simulation result, by applying voltage with single phase, a combined vibration is produced at the surface of an arm of stator. The prototype of motor is fabricated and its outer size is 8 * 4 * 2 mm3 including the cylindrical steel rod of 2 mm in diameter as rotor. The motor exhibits a maximum speed of 500 rpm and a power consumption of 0.3 W when driven at 20 Vpp and 64 kHz.

Dielectric properties of aluminium solid electrolytic capacitor using conduction polymer

Digitalization in electronic systems is required with capacitors which are large capacitance with small size, low impedance at high frequency, and high reliability. The fabrication and properties of aluminium solid electrolytic capacitors are investigated. Employing a conducting polymer film such as, polypyrrole as solid electrolyte, solid type aluminium electrolytic capacitors were made. The surface of insulating oxide is covered with conducting polymer layer prepared by chemical oxidative polymerization. Thereafter this conducting layer is covered with conducting polymer prepared by electrochemical polymerization. The dielectric properties of these capacitors were also measured and discussed. Regarding the frequency characteristics of the trial capacitor, impedance and ESR at high frequency is lower than those of the stacked type film capacitor. It is also confirmed that the temperature coefficient of capacitance and dissipation factor of the capacitor is lower than that of the film capacitor and liquid type aluminium electrolytic capacitor.<<ETX>>

Breakdown phenomena in MIS structure

An alternative to silicon dioxide applied to the gate dielectric in an MIS (metal-insulator-semiconductor) device is silicon nitride. Thin silicon nitride films (thickness <100 AA) were grown by LPCVD (low-pressure chemical vapor deposition) and were characterized by different measured values, such as BDV (distribution of breakdown voltage), TDDB (time-dependent dielectric breakdown), I-V, and C-V. BDV distributions of MNS (metal-nitride-semiconductor) (T/sub N/=5.8 approximately 8.3 nm) are concentrated in the field range of 7 to 8 MV/cm. In the MNS structure (T/sub N/=5.8 to 8.3 nm), two values are obtained from the results of TDDB characteristics, i.e. gamma =0.85 and E/sub a/=0.04 eV. The I-V characteristics of the MIS structure can be explained by mechanisms such as the Schottky effect, Fowler-Nordheim tunnel current, impact ionization, density to trap center, and breakdown. the high effective trap density would enhance the dielectric field strength of the insulating layer. The MNS structure has high permittivity and low V/sub FB/. The thin nitride film processed by LPCVD has relatively high dielectric breakdown strength in the insulating thickness range of 5.8 to 8.3 nm.<<ETX>>

Characteristics of a Miniaturized Ultrasonic Motor for Auto-focusing of a Mobile Phone

In this paper, the design and characteristics of a novel ultrasonic motor are investigated. Such a motor is appropriate for use in the optical zoom or auto focusing functions of the lens system in mobile phones. Its design and simulation of performances are carried out by FEM commercial software (ATILA). The shape of the motor is similar to a square without one side, on which an optical lens can be mounted. Two sheets of piezoelectric ceramics are adhered to both sides of two legs of the elastic body, respectively. To drive the ultrasonic motor, the voltage is applied to two sheets of piezoelectric ceramics bonded to one leg. The rotation direction can be easily changed by switching the piezoelectric sheets bonded to the other leg, to which voltage is applied. A proto type of the motor is fabricated and its outer size is 10*10*2[mm3] including the camera lens of which the diameter is 7.5[㎜]. Its power consumption is about 0.3[W] and the speed of rotation is adjustable from 10 to 200[rpm] according to the applied voltage.

Classification of defects in solid insulation material by PD methods

Solid insulators have good insulation properties. However when they have voids or cracks in the bulk or at the surface, the electric field is concentrated and the insulation material is degraded at this point. Defects in a solid insulation system act as a source of partial discharge (PD). PD is very harmful since it often leads to deterioration of insulation by the combined action of the discharge ions bombarding the surface and the action of chemical compounds that are formed by the discharge. PD can indicate incipient failure, so it has been used to determine degradation of insulation. In this paper, we investigated the classification of PD in defects of solid insulation using a statistical method and classified patterns of PD due to surface discharge, electrical tree and void discharge by using a Kohonen network. To analysis PD we used the distribution of Hqn(q) and parameters such as peak charge, average discharge power, average discharge current, and repetition rate.