• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.5
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• pp.1-7
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• 2012

The transportation is almost dependent on a single fuel petroleum with transportation energy dilemma. Hybrid Electric Vehicle(HEV) technology holds more advantages on efficiency improvements for petroleum consumption at the transportation. And bearing is recognized as the important component of gearbox. Gearboxes for HEV transmission have been ensured the highest reliability over some years in withstanding high dynamic loads. At the same time, the demands of lightweight design and cost minimization are required by thought-out design, high-quality material, superior production quality and maintenance. In order to design a reliable and lightweight gearbox, it is necessary to analyze bearing rating life methods between standard and different bearing companies with calculation methods for modification factors. In this paper, the influence of life time of bearings will be pointed out. Bearing contact stress and load stress distribution of HEV gearbox are obtained and compared with Romaxdesigner and BearinX. And the unequal wear of the left bearing for the gearbox intermediate shaft is investigated between simulation and test.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.4
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• pp.25-30
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• 2012

The transportation is almost dependent on a single fuel petroleum with transportation energy dilemma. Hybrid Electric Vehicle(HEV) technology holds more advantages on efficiency improvements for petroleum consumption at the transportation. And bearing is recognized as the important component of gearbox. Gearboxes for HEV transmission have been ensured the highest reliability over some years in withstanding high dynamic loads. At the same time, the demands of lightweight design and cost minimization are required by thought-out design, high-quality material, superior production quality and maintenance. In order to design a reliable and lightweight gearbox, it is necessary to analyze bearing rating life methods between standard and different bearing companies with calculation methods for modification factors. In this paper, the influence of life time of bearings will be pointed out. Bearing contact stress and load stress distribution of HEV gearbox are obtained and compared with Romaxdesigner and BearinX. And the unequal wear of the left bearing for the gearbox intermediate shaft is investigated between simulation and test.

• Proceedings of the KIEE Conference
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• 1990.07a
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• pp.154-157
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• 1990

This paper describes a new method of calculating expected energy generation and loss of load probability (L.O.L.P) for electric power system operation and expansion planning. The method represents an equivalent load duration curve (E.L.D.C) as a mixture of cumulants approximation (M.O.C.A), which is the general case of mixture of normals approximation (M.O.N.A). By regarding a load distribution as many normal distributions-rather than one normal distribution-and representing each of them in terms of Gram-Charller expansion, we could improve the accuracy of results. We developed an algorithm which automatically determines the number of distribution and demarcation points. In modelling of a supply system, we made subsets of generators according to the number of generator outage: since the calculation of each subset's moment needs to be processed rapidly, we futher developed specific recursive formulae. The method is applied to the test systems and the results are compared with those of cumulant, M.O.N.A and Booth-Baleriaux method. It is verified that the M.O.C.A method is faster and more accurate than any other methods.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.11
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• pp.776-781
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• 2007

Optimized capacity of equipments are essential for energy saving and low cost construction and operation. So we must use proper design data for HVAC system design. We investigated for architectural data, equipment capacity, cooling and heating load design criteria of 52 office buildings. Following research results were obtained by carrying out each task. Office building effective area rate is 63%. The average building cooling load of South Korea is $140W/m^2$ and average heating loads in Seoul and Pusan area are $120{\sim}130W/m^2$ and $70{\sim}80W/m^2$. We also analysised HVAC design criteria. Person ratio in effective building area is $0.2person/m^2$, sensitive and latent heat loads of a person are 60W and 65W, light and equipment loads of office buildings are $25W/m^2$ and $20W/m^2$.

• Wind and Structures
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• v.28 no.6
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• pp.381-388
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• 2019

This paper described the application of Geospatial Analysis in determining mean wind speed, $V_h$ for wind load calculation imposed to electrical transmission tower structural design. The basic wind speed data on available station obtained from Malaysian Meteorology Department is adjusted by considering terrain and ground roughness factor. The correlation between basic wind speed, terrain factor and ground roughness stated in EN-50341-1 is used to obtain the $V_h$ for overhead transmission line elements 50 m above ground. Terrain factor, $k_r$ and ground roughness, $z_0$ in this study are presented by land use types of study area. Wind load is then calculated by using equation stated in design code EN-50341-1 by using the adjusted mean wind speed. Scatter plots of $V_h$ for different $k_r$and $z_0$ are presented in this paper to see the effect of these parameters to the value of $V_h$. Geospatial analysis is used to represent the model of $V_h$. This model can be used to determine possible area that will subject to wind load which severe to the stability of transmission tower and transmission line.

• Aerospace Engineering and Technology
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• v.9 no.2
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• pp.176-184
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• 2010

The power simulator for a LEO satellite is a useful tool to analyze mission validity and energy balance for various mission scenarios by estimating power generation, power consumption, depth of discharge, bus voltage, charging/discharging current, etc. In this paper, it is described the calculation algorithm of the solar array (SA) power, the satellite load power and the battery modeling method to develop a satellite power simulation. To simulate the SA power generation, three different operation modes (DET, MPPT, CV) of SAR (Solar Array Regulator) are considered with a SA model. The satellite load power is estimated using the satellite unit power database, the unit on/off configuration at some satellite operation modes. The bus voltage and battery charging/discharging current at the specific DoD (Depth of Discharge) are calculated based on the battery characteristics. By this satellite power simulator, it can be conveniently analyzed the energy balance and the validity of a planned mission of a LEO satellite.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.835-838
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• 2002

An experiment has been performed using a facility, which simulates the safety depressurization system (SDS) and in-containment refueling water storage tank (IRWST) of APR1400, an advanced PWR being developed in Korea, to investigate the dynamic load resulting from the blowdown of steam from a steam generator through a sparser. The influence of the key parameters, such as air mass, steam pressure, submergence, valve opening time, and pool temperature, on frequency and peak toads was investigated. The blowdown phenomenon was analyzed to find out the real cause of the initiation of bubble oscillation and discrepancy in frequencies between the experiment and calculation by conventional equation for bubble oscillation. The cause of significant damping was discussed and is presumed to be the highly tortuous flow path around bubble. The Rayleigh-Plesset equation, which is modified by introducing method of image, reasonably reproduces the bubble oscillation in a confined tank. Right after the completion of air discharge the steam discharge immediately follows and it condenses abruptly to provide low-pressure pocket. It may contribute to the negative maximum being greater than positive maximum. The subsequently discharging steam does not play as at the driving force anymore.

• Solar Energy
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• v.2 no.1
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• pp.49-58
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• 1982

Aim of this study was to obtain the heating performance and the economic evaluation on solar heating system for greenhouse which area of floor was $90m^2$. For heating performance effective solar energy for the greenhouse was compared with overall heating loads including coefficient of heat transfer and conduction. And the economic evaluation solar heating system was evaluated by comparison its initial investiment costing with oil saving cost. Initial investiment costing included collector cost, storage cost, piping cost, control system cost and miscellaneous costs which included pumps, motors etc. The contents of this study included the survey of climate conditions for solar heating, long-term collector performance and optimum collector area of solar heating system in existing greenhouse. The results are follows: 1. Average horizontal radiation during winter was $2,434Kcal/m^2$ day which was the highest value in this country, so the climate conditions of Suwon was suitable for solar heating. 2. Resulting calculation of the optimum collector area was $30m^2$ and the solar energy accounted for 30% of the overall heating load. 3. The capacity of storage tank required 60 liter per unit area ($m^2$) of solar collector.

• Journal of Energy Engineering
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• v.29 no.3
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• pp.64-73
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• 2020

This paper presented a methodology for calculating daily load curves per city by taking into account the charging/discharging location of electric vehicle. In other words, this is the daily load curve calculation algorithm by city, which takes into account the charging/discharging location of electric vehicles, so that the impact of loads generated by charging/discharging of electric vehicles on the power grid can be easily understood in certain cities. Specifically, in accordance with the PEVs share scenario, the PEVs discharge power was calculated to reflect both the characteristics of the arriving vehicle in the morning and the SMP plan after establishing a assumption that the electric vehicle arrived at work in the morning and the electric vehicle arrived at home in the afternoon for each of the charging/discharging locations, that is, work and home, of electric vehicles in the city. After calculating the daily load curve for each charging/discharging power type for the PEVs charging strategy, which takes into account both the characteristics of the vehicle arriving at home in the afternoon and the TOU fare system, it was analyzed by comparing the impact assessment on the grid by adding the existing load.

• Journal of Power Electronics
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• v.17 no.1
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• pp.136-148
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• 2017

In recent years, voltage source multilevel converters are very popular in medium/high-voltage industrial applications, among which the NPC/H-Bridge converter is a popular solution to the medium/high-voltage drive systems. The conventional finite control set model predictive control (FCS-MPC) strategy is not practical for multilevel converters due to their substantial calculation requirements, especially under high number of voltage levels. To solve this problem, a hierarchical model predictive voltage control (HMPVC) strategy with referring to the implementation of g-h coordinate space vector modulation (SVM) is proposed. By the hierarchical structure of different cost functions, load currents can be controlled well and common mode voltage can be maintained at low values. The proposed strategy could be easily expanded to the systems with high number of voltage levels while the amount of required calculation is significantly reduced and the advantages of the conventional FCS-MPC strategy are reserved. In addition, a HMPVC-based field oriented control scheme is applied to a drive system with the NPC/H-Bridge converter. Both steady-state and transient performances are evaluated by simulations and experiments with a down-scaled NPC/H-Bridge converter prototype under various conditions, which validate the proposed HMPVC strategy.