• Nuclear Engineering and Technology
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• v.55 no.5
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• pp.1577-1586
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• 2023

Safety qualification of a steam generator is a crucial issue related to faulted condition design loads, including earthquake loads, and it should be ensured that the structural integrity of a steam generator does not exceed its design load. Using data from the Gyeongju and Pohang earthquakes, the two most powerful recorded seismic events in Korea, seismic analyses of a typical steam generator are conducted in this study. The modal characteristics are used to develop an input deck for these analyses. With a time history analysis, the responses of the steam generator in the event of an earthquake are obtained. In particular, the displacement, velocity, and acceleration responses are obtained in the time domain, with these outcomes then used for a detailed structural analysis as part of the ensuing assessment. The response spectra are also generated to determine the response characteristics in the frequency domain, focusing on the response comparisons between the Gyeongju and Pohang earthquakes. Structural integrity can be ensured by performing additional analysis using results obtained from the time history analysis considering the input excitations of various earthquakes considered in the design.

• Smart Structures and Systems
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• v.22 no.2
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• pp.139-150
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• 2018

A variable electromotive-force generator (VEG), which is a modified generator with an adjustable overlap between the rotor and the stator, is proposed to expand the operational range of a regular generator through a simple and robust active control strategy. It has a broad range of applications in hybrid vehicles, wind turbines, water turbines, and similar technologies. A mathematical model of the VEG is developed, and a novel prototype is designed and fabricated. The performance of the VEG with an active control system, which adjusts the overlap ratio based on the desired output power at different rotor speeds for a specific application, is theoretically and experimentally studied. The results show that reducing the overlap between the rotor and the stator of the generator results in reduced torque loss of the generator and an increased rotational speed of the generator rotor. A VEG can improve the fuel efficiency of hybrid vehicles; it can also expand operational ranges of wind turbines and water turbines and harness more power.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.211-215
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• 2006

In this paper, design and applications of a generalized, versatile and customizable IF signal generator that can model the modernized GPS and Galileo signal is given. It generates IF sampled data that can be directly used by a software receiver. Entire constellation of satellites which is independent of satellite-user geometry is easily determined using a real or simulated ephemeris data. Since the IF center frequency, sampling frequency and quantization bit number are user location dependent parameters, their effects are also considered in IF signal generator. The generalized IF signal generator will be very well suited for the development phase of a software receiver due to its versatility. The full access to the sampling frequency, front-end filter definition and ADC parameters also offers a great opportunity for cost-effective analysis of tracking loops and error mitigation techniques at the receiver level. Interference sources can be easily added to the generator to simulate specific environments. This software IF signal generator can also be used to feed a multi-frequency multi-system software receiver for the prototyping of a combined GPS/Galileo receiver. The test result using the generated signals and a real software receiver shows the effectiveness of the implemented IF signal generator.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.837-842
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• 2000

In the coiling process of helical steam generator tubes of integral reactor SMART, a considerable amount of spring back, which induces dimensional inaccuracy and difficulty in fabrication, has been arised. In this research, an analytical model was derived to evaluate the amount of the spring back for steam generator tubes. The model was developed on the basis of beam theory and elastic-perfectly plastic material property. This model was extended to consider the effect of plastic hardening and the effect of the tensile force on the spring back phenomena. Parametric studies were performed for various design variables of steam generator tubes in order to minimize the spring back in the design stage. A sensitivity analysis has shown that the low yield strength, the high elastic modulus, the small helix diameter, and the large tube diameter result in a small amount of the spring back. The amount of the spring back can be controlled by the selection of adequate design values in the basic design stage and reduced to an allowable limit by the application of the tensile force to the tube during the coiling process.

• Proceedings of the KIEE Conference
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• 2005.10c
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• pp.26-28
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• 2005

Induction generator is the most common generator in wind energy systems because of its simplicity, ruggedness, little maintenance, price and etc. But the main drawbacks in induction generator is its need of reactive power means to build up the terminal voltage. This drawback is not an obstacle today where PWM inverters can accurately supplies the induction generator with its need from reactive power. For a insurance of three-phase induction generator requires capacitive reactance of the terminal. Most of previous work uses numerical iterative method to determine this minimum capacitor. But the numerical iteration takes long time and divergence may be occurs. In this paper is presented the design methods of the minimum self-excited capacitor required for induction generator operation. And a new formula from the equivalent circuit for stable generation operation of self-excited induction generator calculates the proper capacity to obtain the terminal voltage of the load stage. The validity of proposed design methods is confirmed by experimental and computed results.

• Journal of Electrical Engineering and Technology
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• v.13 no.6
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• pp.2187-2195
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• 2018

In order to realize the multi-objective control of single-input multi-output nonlinear differential algebraic system (NDAS) and to improve the dynamic characteristics and static accuracy, a design method of nonlinear control with multi-objective feedback (NCMOF) is proposed, the principium of this method to arrange system poles, as well as its nature to coordinate dynamic characteristics and static accuracy of the system are analyzed in detail. Through NCMOF design method, the multi-objective control of the system is transformed into linear space, and then it is effectively controlled under the nonlinear feedback control law, the problem to balance all control objectives caused by less input and more output of the system thus is solved. Applying NCMOF design method to generator excitation system, the nonlinear excitation control law with terminal voltage, active power and rotor speed as objective outputs is designed. Simulation results show that NCMOF can not only improve the dynamic characteristics of generator, but also damp the mechanical oscillation of a generator in transient process. Moreover, NCMOF can control the terminal voltage of the generator to the setting value with no static error under typical disturbances.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.3
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• pp.80-87
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• 2012

This paper suggests the slot wedge shape for reducing the cogging torque of a direct-drive permanent magnet synchronous generator for a bike. To consider easy coil winding, we applied a structure of open slot for the permanent magnet synchronous generator (PMSG). Because the cogging torque of PWSG with the open slot is very large, we are designed the appropriate specifications of the PMSG by selected the appropriate material of slot wedge and various slot wedge shapes. The prototype model is selected by design theory for reducing cogging torque and maximizing efficiency of PMSG. And the detailed structure design of the model was designed by the loading distribution method. The PMSG models were analyzed by finite element method. Finally, we have suggested appropriate material of slot wedges and its shape which has benefit to further reducing cogging torque and preventing decreasing of the generating power.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.1
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• pp.34-39
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• 2002

Most X-ray generator had been used do rectifier type transformer high tension generator which is supplied in a clinical diagnosis. But it is difficult to miniaturize and become light weight. Also, because the ripple rate of tube voltage is high, X-ray generating efficiency is very low. Therefore, it is supplied gradually from abroad being developed high tension generator for inverter type X-ray generator which use semi-conductor switching element for electric power that have high speed switching ability to solved these problem. But, semi-conductor element of big capacity are used by X-ray tube's big consumption power and diffusion is difficult in the small size hospital because production cost is ascending by doing digital control through DSP and product price becomes expensive. Therefore, in this paper, design and manufactured CR type voltage divider for feedback control of tube voltage of high frequency resonance type inverter and high tension transformer for high frequency to apply economical diffusion type X-ray generator which have wide output voltage and load extent. It is Proved do X-ray generator and stability of X-ray tube's output characteristics through an experiment.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.05a
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• pp.849-853
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• 2009

A generator is in use for a moving vehicle like car, aircraft, ship as well as key industry including a thermal power plant, a water power plant, a nuclear power plant, and so on. Such the AC generator plays an important role in vehicle, ship, aircraft, and so forth, at the point of generating electric power. Especially in the matter of the ship, the emergency generator system is mounted to provide against malfunction of main generator on a voyage. So, it is ordered that the system can monitor the main generator and operate the emergency generator when the emergency happens. This study is about controller for the emergency diesel engine generator and design of a various software.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.451-453
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• 2012

Conceptual design and manufacturing scheme of a gas generator for 7 tonf class rocket engine were described. The combustion chamber pressure, O/F ratio, and total flow rate were decided to be 6 MPa, 0.321, and 1 kg/s respectively in consequence of the engine system design. Based on the parameters conceptual design of the gas generator was carried out and its outer dimension was about ${\Phi}100{\times}250mm$. Most parts of the gas generator to be jointed together by brazing or TIG welding and, if possible, the strength and leakproof tests are to be conducted in every step for checking the welding section.