• Laser Solutions
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• v.3 no.1
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• pp.12-20
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• 2000

The nuclear steam generators are subjected to corrosion environmental condition during operation that can result in stress corrosion in the tube wall. If any tube wall degradation is recognized, the tube must be repaired by plugging or sleeving. For the sleeving repair, Nd : YAG laser welded sleeving technology is one of the most promising when considering radioactive working conditions in the nuclear power plant. In this paper, the laser welding characteristics of steam generator tube and sleeve materials are investigated. The effects of average laser power, laser energy, welding speed, pulse duration and frequency are evaluated. Based on these results, Nd : YAG laser welded sleeving repair was applied to the degraded steam generator tubes in real environment.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.4
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• pp.179-184
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• 2003

The pulsed power system is widely used for many industries and environments. Generally, we call the "RUST", the reddish brown surface, that was made on iron surface or some other metals, when they are contacted by water and air the main substance of rust is oxide-ionization. In other words, the chemical symbol of rust on iron surface is iron oxide(III) hydrate Fe203.nH2O. In this study, we have designed and fabricated our system which has a compact pulse generator with switching MOSFET. Also we have studied the metal-oxide removing characteristics using in the atmospheric arc discharge. It has been investigated their removing characteristics by the change of charging voltage and pulse repetition rates. From this result, we can find out that the removal area Is increased from 3.80 to 8.04[$\textrm{cm}^2$], when pulse duration is increased from 100[pps] to 400[pps]. 400[pps].

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.3
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• pp.314-319
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• 2015

Invar is a compound metal of Fe-Ni system contained 36.5% Ni. The characteristic of invar is that the coefficient of thermal expansion is $1.0{\times}10^{-6}cm/^{\circ}C$. It is approximately 10 times smaller than series of steel. Because of this low thermal expansion characteristic of Invar, it is used to shadow mask of display device such as UHDTV or OLED TV. In this study, pulse current from pulse generator instead of DC current is used to overcome the disadvantages of the conventional electrochemical machining. Pulsed current with different duty factor in PECM affect the precise geometry. Pulse electrochemical machining is conducted to machine the micro hole to the invar sheet with different duty factor. The machined shape and overcut of invar sheet with different duty factor is observed by optical microscope and scanning electron microscope (SEM).

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.4
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• pp.45-49
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• 2007

When drilling using electrical-discharge machining (EDM), severe electrode wear makes in-process measurements of the depth of the drilled hole and the volume of material removed impossible. To estimate the volume of material removed a reliable real-time discharge pulse counting method is proposed by assuming that the volume removed in EDM is proportional to the number of discharge pulses from an iso-energy pulse generator. The geometry of machined holes, including depths and cross-sectional profiles, is estimated using geometric analysis. A proportional relationship between the volume of material removed and the number of discharge pulses was developed and verified by experiments.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.10a
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• pp.568-572
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• 2000

This paper describes the experimental results of a transient impedance characteristics of grounding rods to a square pulse and standard lightning impulse current. The test were performed on single grounding rod($\phi$ 10mm, 1m) and triple-grounding rods( $\phi$ 10mm, 1m) of equilateral triangles with 5m spacing. For measurements of transient impedance, a pulse generator which can produce square wave of 30ns rise time and 20U Pulse duration was designed and fabricated. In the experiment, transient impedance of the grounding systems have been investigated from the recorded potential and current waveforms. The results showed that the value of the transient impedance is quite higher than the stationary resistance, and provide useful information for the value of a grounding system considered transient characteristics under a high frequency condition such as lightning stokes and ground-fault.

• Journal of Advanced Navigation Technology
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• v.3 no.1
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• pp.1-12
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• 1999

For the phase measurement of radar signal in the coherent-on-receiver system, the COHO(Coherent Oscillator) generates the signal which locks to the phase of the transmit pulse. In this paper, COHO unit is developed to generate 60 MHz phase-locked signal. ILO(Injection Locking Oscilator) locks to the sample of the transmit pulse. Gate circuit, ILO, buffer amplifier, and pulse generator are designed and implemented.

• Journal of Sensor Science and Technology
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• v.24 no.3
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• pp.145-150
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• 2015

We introduce a new method of time-division visible light communication (VLC) using LED lamp light for the generation of synchronizing pulses. The LED lamp, driven by an AC 220-V power line, radiates light that has a 120-Hz frequency component. The pulse generator in each VLC system receives the LED lamp light and generates the synchronizing pulses that are required for time-division transmission of multiple VLC channels. The pulse period is subdivided into several time slots for VLC channels. In experiments, 120-Hz synchronizing pulses were generated using LED lamp light, and three VLC channels were transmitted independently without interfering with each other in a condition where the VLC signals overlapped in space. This configuration is useful in constructing multiple wireless sensor networks that are safe and without interference in locations where LED lamps are used for illumination.

• Proceedings of the KIEE Conference
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• 1997.07e
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• pp.1737-1739
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• 1997

We describe the characteristic of LVI test system and methods to detect the deformation of windings in the power transformers. As the front rise time of recurrent-surge generator pulse less than 1000ns and the peak value of pulse is about 500V, we have the good results of detecting winding deformation in the LVI test of transformer. And we discuss the application of LVI test method and the condition of RSG pulse through results of in one and three pole transformers under Lab. tests.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.10
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• pp.139-147
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• 1996

In this study a two-stage fast pulse generaor using magnetic switches is proposed. The scheme consist of a switch, an inductor and two pairs of capacitor and saturable inductors, a linear transformer. The basic principle and the operation are described using a set of given parameters. The main issue of the magnetic pulse genration scheme is the system efficiency. This study focuses on the system efficiency improvement using magnetic switches. The voltage compression ratio, energy transfer with respect to core area are investigated. The output voltage and transferred energy as a function of input voltage are also included. Also, an analysis and experiments are performed to verify the porposed topology by implementing a 10[J] class experimental circuit. The efficiency of the transferred energy a tload side is 82%.

• Journal of Korean Vacuum Science & Technology
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• v.7 no.2
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• pp.45-56
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• 2003

A high flux metal plasma pulse ion source, which can simultaneously perform ion implantation and deposition, was developed and tested to evaluate its performance using the prototype. Flux of ion source was measured to be 5 A and bi-polar pulse power supply with a peak voltage of 250 V, repetition of 20 Hz and width of 100 ${\mu}\textrm{s}$ has an output current of 2 kA and average power of 2 kW. Trigger power supply is a high voltage pulse generator producing a peak voltage of 12 kV, peak current of 50 A and repetition rate of 20 Hz. The acceleration column for providing target energy up to ion implantation is carefully designed and compatible with UHV (ultra high vacuum) application. Prototype systems including various ion sources are fabricated for the performance test in the vacuum and evaluated to be more competitive than the existing equipments through repeated deposition experiments.