• Journal of Industrial Technology
• /
• v.22 no.B
• /
• pp.89-93
• /
• 2002

When testing products before shipment to the customer, quality characteristics are measured to decide whether or not their values are between the specification limits. Unfortunately, this testing procedure can lead to incorrect decisions because of gauge error. That is, good products can erroneously be qualified as bad, and bad products as good, and this has consequences for producer's and consumer's risk. In cases of such as this, the compressed gauge limit can be used to achieve the desired product quality level dictated by the manufacturer or the customer. A compressed gauge limit is a limit set by the manufacturer on a test gauge that is tighter than the specification limit established by the customer. The compressed gauge limits should be set at levels to achieve the defect levels desired by the customer and simultaneously minimize the loss of good product that is rejected due to errors in the gauges. In this article, the models for determining the defect levels and the losses obtained by adding compressed gauge limits will be developed. A response surface model approach is utilized which allows an optimal operating condition to be generated relatively easily.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.15 no.2
• /
• pp.1-8
• /
• 2019

The integrity of the Reactor Pressure Vessel (RPV) is affected by the neutrons bombarding the vessel wall leading to embrittlement. This irradiation-induced embrittlement leads to reduction in the fracture toughness of RPV materials. This paper presents a comparative study of typical Optimized Power Reactor (OPR)1000 reactor pressure-temperature (P-T) limit curves using the pre-2006 American Society of Mechanical Engineers (ASME) editions used in the power plant and the current ASME edition of 2010. The current ASME Code utilizes critical reference stress intensity factor based on the lower bound of static, while the Pre-2006 ASME editions are based the critical reference stress intensity factor based on the lower bound of static, dynamic and crack arrest. Model-Based Systems Engineering approach was used to evaluate ASME Code Section XI Appendix G for generating the P-T limit curves. The results obtained from this analysis indicate decrease in conservatism in P-T limit curves constructed using the current 2017 ASME code, which can potentially increase operational flexibility and plant safety. Hence it is recommended to use ASME code edition after 2006 be used in all operating nuclear power plants (NPPs) to establish P-T limit curve.

• Proceedings of the KIEE Conference
• /
• 1993.07b
• /
• pp.1013-1015
• /
• 1993

The switched reluctance motor is excited and controlled by two kinds of excitation; chopped excitation and switched excitation. The former produces additional inverter losses, and onuses drive control to be complicated. The limit of chopping frequency reduces a range of operating speed and torque. This paper examines chopped excitation and switched excitation in a nonlinear switched reluctance motor. The result indicates switched excitation can be satisfactorily applied to the full operating range, and furthermore indicates the improved efficiency.

• Proceedings of the KIEE Conference
• /
• 2005.07a
• /
• pp.816-818
• /
• 2005

In this paper, we have developed an hourly operating strategy for Direct load control (DLC) considering the efficiency of DLC program and increasing the utility of DLC resource. According to the operating code for DLC, the DLC center should curtail the load for 4 hours when the control notification has been enforced. Since the above strategy may limit the participation of entities, who intend to take part in the DLC program, the new strategy to mitigate the above limitation is required. In this paper, we have developed the operating strategy of DLC program and the mechanism to apply the proposed strategy in the DLC center. The proposed strategy makes the important role from the view of guaranteing the effective alternative raising the participation and avoiding the penalty of the entities.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.55 no.10
• /
• pp.440-445
• /
• 2006

As an electricity industry transforms into a competitive system, an electricity market revolves into a combined market consisting of generation and operating reserve. This paper presents a market model combined by an energy market and an operating reserve market. In a competitive structure, Gencos strive to choose strategic bidding parameters that maximize total profit resulting from an energy market and a reserve market. The primary goal of the paper is to analyze power transactions of generation and operation reserve based on marginal profits and capacity limits at NE(Nash Equilibrium). In case studies, the reserve market and the energy market are compared at the n from the viewpoints of marginal profits, prices and transaction quantities. It is shown that the marginal profit in an energy market is equal to that in a reserve market, and Gencos strategic bidding is greatly influenced by capacity limit.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.30 no.8 s.251
• /
• pp.993-1000
• /
• 2006

Operating experience of steam generators has shown that cracks of various morphology frequently occur in the steam generator tubes. These cracked tubes can stay in service if it is proved that the tubes have sufficient safety margin to preclude the risk of burst and leak. Therefore, integrity assessment using exact limit load solutions is very important for safe operation of the steam generators. This paper provides global and local limit load solutions for surface cracks in the steam generator tubes. Such solutions are developed based on three-dimensional (3-D) finite element analyses assuming elastic-perfectly plastic material behavior. For the crack location, both axial and circumferential surface cracks, and for each case, both external and internal cracks are considered. The resulting global and local limit load solutions are given in polynomial forms, and thus can be simply used in practical integrity assessment of the steam generator tubes.

• Structural Engineering and Mechanics
• /
• v.53 no.6
• /
• pp.1271-1286
• /
• 2015

Recently, US NRC revised fracture toughness requirements as 10CFR50.61a to reduce the conservatism of 10CFR50.61. However, unlike previous studies relating to the initial regulation, structural integrity evaluations based on the alternative regulation are not sufficient. In the present study, PTS and P-T limit curve evaluations were carried out by using both regulations and resulting data were compared. With regard to the PTS evaluation, the results obtained from the alternative requirements were satisfied with the criterion whereas those obtained from the initial requirements did not meet the criterion. Also, with regard to the P-T limit curve evaluation, operating margin by 10CFR50.61a was greater than that by 10CFR50.61.

• Nuclear Engineering and Technology
• /
• v.30 no.3
• /
• pp.222-234
• /
• 1998

The Westinghouse OT$\Delta$T DNB protection logic heavily restricts the operation region by applying the same logic for a full range of operating pressure in order to maintain its simplicity. In this work, a fuzzy neural network method is used to estimate the DNB protection limit using the measured average temperature and pressure of a reactor core. Fuzzy system parameters are optimized by a hybrid learning method. This algorithm uses a gradient descent algorithm to optimize the antecedent parameters and a least-squares algorithm to solve the consequent parameters. The proposed method is applied to Yonggwang 3&4 nuclear power plants and the proposed method has 5.99 percent larger thermal margin than the conventional OT$\Delta$T trip logic. This simple algorithm provides a good information for the nuclear power plant operation and diagnosis by estimating the DNB protection limit each time step.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.25 no.8
• /
• pp.82-87
• /
• 2011

Induction motor is most widely used as the driving power in the industrial site. Induction motor current is composed of two parts, magnetizing current and load current. Load current uses energy what is doing the work. Load current varies with load variance but magnetizing current is constant, regardless of load variation. Magnetizing current needs for establishing the rotating magnetic field of induction motor and lags behind the voltage. Generally capacitor is used for power-factor compensation of inductive load. Self-excitation occurs when the capacitive reactive current from the capacitor is greater than the magnetizing current of the induction motor. When this occurs, excessive voltages can result on the terminals of the motor. This excessive voltage can cause insulation degradation and ultimately result in motor insulation failure. In this paper, we analyzed that how the magnetizing current and condenser current is operating at the allowable limit by the load variation. Condenser current is below allowable limit of magnetizing current but magnetizing current is above allowable limit at the lower load operation condition.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.19 no.1
• /
• pp.1-8
• /
• 2016

In this paper, we have described the performance improvement of surveillance radar to prevent damage or malfunction of surveillance radar RF head unit due to the strong reflections caused by artificial obstacles at close range. We have proposed a technique to improve the performance of the RF head unit as a solution to overcome the limitations of the operating system and improve radar performance. We have verified the effectiveness of the improvement by comparing the before and after results applied to actual system.