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  • 1.
    Gholinejad, Hassan
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Mousavi Takami, Kourosh
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Dahlquist, Erik
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling. Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Estimation of electricity losses by numerical approach to present a solution for losses reduction2014Ingår i: International Journal of Advanced Engineering Applications, ISSN 2321-7723, Vol. 7, nr 4, s. 30-40Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Electricity losses are one of the big anxieties for utilities. Electricity loss in Iran network according to Tavanir report is over 15% but individual researchers have different comments. Also, the lack of sufficient information is a network problem. To overcome on the problems authors used Top-Down/Bottom-Up method to estimate of losses in Iran’s electricity network. To achieve the model, at a certain moment measurements of input complex power in the feeder and voltages in the farthest network node and power flow calculation has been done. Using the estimated losses, authors suggest a strategy to losses reduction in every different part of distribution networks. Due to different culture, climate and network topology, losses are different and separate solution is needed. Proposed method was carried out by performing tests on a feeder with 88+35 nodes according to the IEEE 123 node test feeder. An economical investigation showed the benefits for utilities and improved the proposed plan. The main innovation in the presented paper is to combine a forecasting approach with experimental data to define a model for networks with unknown parameters.

  • 2.
    Gholinejad, Hassan
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Mousavi Takami, Kourosh
    Mahmoudi, Jafar
    Description of techniques for hot spot monitoring and detection in power transformers2008Ingår i: Energitinget Scientific Conference 2008, 2008Konferensbidrag (Refereegranskat)
  • 3.
    Gholinejad, Hassan
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Mousavi Takami, Kourosh
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Mousavi Takami, Amin
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Dahlquist, Erik
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling. Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    To promote electricity smart grid performances by numerical modeling applications2014Ingår i: Proceedings of the 55th Conference on Simulation and Modelling(SIMS 55): “Modelling, Simulation and Optimization” / [ed] Alireza Rezania Kolai, Kim Sørensen & Mads Pagh Nielsen, Linköping: Linköping University Electronic Press, 2014, s. 347-355Konferensbidrag (Refereegranskat)
    Abstract [en]

    Wide world’s utilities are generating, transmitting and distributing of electricity throughout the country andare responsible to its quality.Distributed automated distribution system has been proposed for planning to reduce losses, optimize capacityand load balancing in electricity networks. The world electricity average loss is about and outage percustomer time is about min/ year. The indices are needed to optimize in developing countries.This paper deals on a modeled distribution system in Sari distribution region and evaluates three mentionedparameters on network quality. Restoration, maneuvers to achieve the minimum loss, reactive powercontrolling, load balancing etc are investigated.Modeling performs by MATLAB software, EMTP for transient modeling and Digsilent with real data bySari Distribution Company. In this paper, a new approach by rearrangement aimed at reducing losses andimproving of load balancing in distribution networks was presented.

    Keywords: Modelling, smart grid, electricity network

  • 4.
    Mousavi Takami, Kourosh
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Optimization of Kanthal Superthal High Power Reflectors2008Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Kanthal AB, the market's foremost supplier of heating solutions to industry, often creates optimum solutions for each customer. One of their solutions is the High Power Reflector, which consists of a vacuum formed ceramic fibre 'hood' with an integrated Kanthal Super ceramic heating element. The performed project is to optimize heat performance of the High Power Reflector with respect to output power and temperature distribution. The task was solved using heat transfer simulations in with reflector different models. The simulation in COMSOL software environment in two-dimensional was performed to find the best reflector shape. Authors have simulated five different types of proposed reflectors. The temperature distributions were simulated as well as temperature profile and curve in 20 cm on the top of element until 50 cm have obtained, in this way with respect to higher out power and uniform temperature distribution, was found the optimized model of reflector and hood for using in power heating system. For verification used the three-dimensional simulation. It is shown that the difference is less than of 3%. Results have a satisfied fit with furnace average temperature. In this research Kanthal AB handbook has been our reference for comparison. In future work to verify the simulations, tests can be performed at Kanthal's facilities.

     

  • 5.
    Mousavi Takami, Kourosh
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Process Control and Simulation of Ferromagnetic Strip in the Power Transformers and Electrical Machines Applications: Electric power systems2009Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Denna avhandling behandlar optimering och kontroll av elektrisk och termisk utrustning med hjälp av FEM och CFD-modellering i kombination med dynamiska simuleringsmodeller.

    Avhandlingen fokuserar på produktion av remsor och styrsystemet i syfte att minska förluster och ge bättre magnetiska egenskaper. Flera parametrar och faktorer bidrar till förluster i kärnan. Tjockleksavvikelser i remsor, höga nivåer av föroreningar i kärnan, orientering, åldrande, yta oxidation, överbelastning och temperaturer i heta punkter finns bland orsakerna till förlusterna i kärnan. Några av de förluster som uppstår under klippning av remsor och ihopsättningen av kärnan. Denna avhandling fokuserar på att minska förlusterna i produktionsstegen för kallvalsning och  glödgning.

    Kallvalsningen har ett direkt inflytande på riktigheten av remsornas tjocklek och magnetiska åldrande. Vissa störningar i till exempel excentriciteten, gapet mellan valsarna, form och kanter måste minimeras för att uppnå korrekt tjocklek. Tjockleksmätningar utgör en viktig del av utvärderingen av förluster  i elektrisk utrustning. Föroreningar och smutsiga bandytor i kallvalsningssteget kan öka kolhalten i band som passerar genom ugnar efter kallvalsning. Valsämnet bör rengöras innan avhaspling och upprullning.

    När bandet passerar genom glödgningsugnar bör temperaturen vara homogen över hela remsan. Enligt simuleringar av ugnen och remsans temperatur kan homogen temperatur uppnås med elektriska värmeelement (Molybden disilikat, MoSi2) insatta i reflektorer. De kan ersätta den gaseldade brännare som för närvarande används.

    Modellering av kallvalsningsprocessen sker i syfte att hitta korrelation mellan styrsystemparametrar. En multivariabel matematisk modell för valsningsprocessen har tagits fram som använder korrelation mellan variabler. Denna metod ger numeriskt effektiva algoritmer som behövs för att köra i en realtids-miljö.

    En modell har tagits fram för att bestämma remsornas med tjocklek för kontinuerlig och icke-kontinuerligt tillstånd med hjälp av en robust algoritm. Det kritiska problemet i reglerloopen för tjocklek har analyserats, och en adaptiv regleralgoritm föreslås.

    Ett antal metoder har undersökts för att förbättra de slutliga bandegenskaperna. Avvikelser i kallvalsade band med avseende på tjocklek, excentriciteter och form kompenseras. Simuleringsresultaten har verifierats med mätdata och de viktigaste källorna till störningar upptäckts.   Slutligen, för att lösa problemet med heta punkter i stora transformatorer föreslås en ny metod för oljesprutning, vilken också analyseras i avhandlingen.

  • 6.
    Mousavi Takami, Kourosh
    Mälardalens högskola, Institutionen för samhällsteknik.
    Temperature and heat losses simulation in core and winding of a power transformer2008Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Simulering av temperatur och värmeförluster i kärna och lindning för en högspänningstransformator

    “... Ett ljus som lyser dubbelt så starkt, varar hälften så länge …”, i analogi med ljuset så kan transformatorer köras med överlast inom vissa gränser, men med följden att livslängden blir kortare.

     

    Transformatorn är vital del i en kraftindustri; transformatorn står för en betydande del av investeringen i en kraftanläggning. Tekniska livslängden för en transformator är cirka 30 år, men överlast kan förkorta livslängden. Överlast orsakar heta punkter i transformatorlindningen och kärnan och leder till nedbrytning av isoleringsförmåga samt orsakar förkortad livslängd och kylproblem. Det finns ett ökande intresse i att nyttja hela transformatorns kapacitet och samtidigt hålla sig inom säkra gränser. För att konstruera en transformator behövs kunskap om dynamik under varierande last, temperaturer i heta punkter, temperaturer i lindningen och förluster. Data kan erhållas genom att mäta på transformatorer, ställa upp och använda analytiska uttryck och utföra datorsimuleringar. Att bygga simuleringsmodell före fysisk prototyp har fördelen att man enkelt kan prova konsekvenserna av ändringar i transformatorns parametrar innan man bygger prototypen.

     

    Under driften av transformatorn är temperaturen i den heta punkten den kritiska parametern. Temperaturen i heta punkten får inte överskrida en viss temperatur. Den sammanlagda effekten av åldring av isolering på grund av temperaturen i heta punkten bör också ligga lägre än ett förutbestämt värde.

    Nya metoder behövs för detektion, övervakning och eliminering av heta punkter. I avhandlingen föreslås en ny apparatur och system för eliminering av heta punkter. Oljesprutningens effekt på transformatoroljan och oljecirkuleringen har utvärderats, simulerats och beräknats. Baserat på data och mätningar från en transformatorstation 230/63/20 kV i Sari i Iran har det utförts beräkningar och simuleringar. Resultaten visar att elektrisk nyttig energi kan ökas genom att minska begränsningarna i last på grund av problem med heta punkter i transformatorer. System för sprutning av olja är undersökta och modifierade för lokal kylning. En robust algoritm har föreslagits, utvecklats och optimerats för ökad noggrannhet i kylningen. Ett viktigt resultat är möjligheten att simulera temperaturer, speciellt heta punkter och förluster i magnetiska kärnan och lindningarna.

  • 7.
    Mousavi Takami, Kourosh
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Dahlquist, Erik
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Modeling and Simulation of Short Circuit Current and TRV to Develop a Synthetic Test System for Circuit Breakers2014Ingår i: Proceedings of the 55th Conference on Simulation and Modelling (SIMS 55), 2014, Vol. 108, s. 285-292Konferensbidrag (Refereegranskat)
    Abstract [en]

    A parallel injection of short circuit current and transient voltage to medium and high voltage circuit breaker (CB) by a synthetic model is studied. Transient recovery voltage is created by a capacitor bank and is applied to CB. Also short circuit current is supplied by a 20/0.765 Kv short circuit transformer. Texas DSP is used as controller and programmed in code composer.To test of circuit breakers by synthetic test equipments, an accurate control system can satisfy the test criterion. An optical triggered spark gap has been used to interrupt short circuit current and to initialize of transient recovery voltage (TRV) that is applied across the contacts of circuit breaker. Modeled results are verified by a laboratory based synthetic test system. Test object CB is a 24 Kv, 25 KA with vacuum type chamber. To find a desired sequence to open/close of backup- test object and auxiliary circuit breakers within appropriate time to inject of recovery voltage is main goal of the presented paper. Modeling and simulation has been done in MATLAB software. Test procedure has been done under IEC 62271-100 , 62271-101.

  • 8.
    Mousavi Takami, Kourosh
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Dahlquist, Erik
    Power transformer parameter estimation with on-line data aquisition using the Kalman filter method2008Konferensbidrag (Refereegranskat)
  • 9.
    Mousavi Takami, kourosh
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Gholinejad, Hasan
    Mahmoudi, Jafar
    Thermal and hot spot evaluations on oil immersed power Transformers by FEMLAB and MATLAB software’s2007Ingår i: EuroSime 2007: International Conference on Thermal, Mechanical and Multi-Physics Simulation Experiments in Microelectronics and Micro-Systems, 2007, 2007, s. 529-534Konferensbidrag (Refereegranskat)
    Abstract [en]

    Transformers are important and expensive elements of a power system. Inordinate localized temperature rise, hottest spot temperature (HST), causes rapid thermal degradation of insulation and subsequent thermal breakdown. To prescribe the limits of short-term and long-term loading capability of a transformer, it is necessary to estimate the HST of transformer winding to as high a degree of accuracy as can possibly be made. These papers have now improved the accuracy of estimation of hottest spot temperature. Inordinate temperature rise in a power transformer due to load current is known to be the most important factor in causing rapid degradation of its insulation and decides the optimum load catering ability or the load ability of a transformer. The Top Oil Temperature (TOT) and Hottest Spot Temperature (HST) being natural outcome of this process, an accurate estimation of these parameters is of particular importance. IEEE / IEC among others have proposed procedure to estimate the temperatures, however, the accuracy of the predictions are not always as good as are desired. Unacceptable temperature rise may occur due to several fault conditions other than overloading, and hence warrant an online monitoring of the transformer.

  • 10.
    Mousavi Takami, Kourosh
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Hekmat, Homa
    Tehran Medical University, obstetrics and genecology dep..
    Simulation and Calculation of Magnetic and Thermal Fields of Human using Numerical Method and Robust Soft wares2008Manuskript (Övrigt vetenskapligt)
    Abstract [en]

    A numerical calculation and simulation of the bio-heat transfer and magnetic flux equations has been presented in this article. It expresses heat and magnetic distribution and transfer phenomena within the human body.Magnetic simulation on the body using a predefined electrical and magnetically models has been performed. A 40-cylindersegment model was used as the geometry of the human body. Thermal infrared (IR) images were used to verifications of claims.Comparisons of IR images with their simulated and calculated models indicate that this method is effective in eliminating the influence of the thermal environmental and magnetic conditions. However, the difference between the images and the computerized results varies among segments.Our computer simulation can predict the skin and tissue temperature and magnetic fields distribution; it is valuable in that a user can employ it to various change parameters reflecting environmental and physiological conditions.

  • 11.
    Mousavi Takami, Kourosh
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Jafar, Mahmoudi
    A novel device (oil spraying system) for local cooling of hot spot and high temperature areas in power transformer2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    Power transformer is a vital device in substations. Load and no load losses create a hot spot point in transformer, so it is obviously necessary to limit the core temperature to values that cause no damage to the core itself, adjacent materials, or the oil. Core temperatures as low as 110 C–120 may degrade oil. This has led experts in the field to suggest that 130 C would be a reasonable limit for the core temperature. For this reason, need to a device for local cooling is necessary. Authors in this paper find a novel method for oil cooling in hot spot point or area. Oil spraying device is simulated and then path of pressured oil after shooting in hot spot point, is evaluated. With using of 230/63/20kv Punel substation in Iran data, and after simulation and calculation, authors find that with using of this device utilities could remove their problem for over loading of transformers in the load peak time.

  • 12.
    Mousavi Takami, Kourosh
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Jafar, Mahmoudi
    danielson, Örja
    High temprature power reflector simulation using of COMSOL software's2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    Super heater elements concentrated in very high and clean power at temperature up to 1800 ºc is needed for aluminium melting, oil drying equipment using for power transformers and same that material. There fore, always it is need to minimize power consumption and increase effectiveness at power reflector customers. This means to minimize heat losses in the High Power Reflector, and to optimize heat performance with respect to output power and temperature distribution. This can be done by altering the size and form of the insulating ceramic fiber to have as much power as possible 'reflected' out from the module. It can also be done by altering the size and form of the element.It has been done and the task solved mainly by heat transfer simulations, using COMSOL and MTLAB software’s. To minimize the number of different designs (and thus the number of calculations) were studied; it is also done that statistical methods for experimental design used to determine which designs should be used in the calculations.When an optimal solution has been found, it has been tested at Kanthal's facilities, with two reference designs.

  • 13.
    Mousavi Takami, Kourosh
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Mahmoudi, Jafar
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    A new apparatus for mitigating the hot spot problem in large power transformers using Ants algorithm2007Ingår i: IEEE PES PowerAfrica 2007 Conference and Exposition, PowerAfrica, 2007, s. 587-594Konferensbidrag (Refereegranskat)
    Abstract [en]

    Hot spot temperature (HST) is the most important parameter in the operation of power transformers. The HST has to be held under a prescribed limit. HST has a considerable effect on the insulation aging. Therefore detecting, monitoring and removing the HST could be a very important and necessary action for Utilities. A new design of oil spraying and its effect, along with a thermal management in a transformer cooling system has been studied in this paper. The effect of oil fluid flow on the HST problem has been considered in this paper; and the calculations and simulation have been performed by Ants algorithm. The simulation results have been validated based on a 230/63/20 kV, 250MVA transformer at the Sari substation in Iran, and the results indicate that the new design could mitigate the limitations of transformer loading due to the HST problem. The Ants algorithm have been proposed and applied for accomplishing this task and to give an improved level of accuracy.

  • 14.
    Mousavi Takami, Kourosh
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Mahmoudi, Jafar
    Design of a new oil spraying device for hot spot cooling in large scale electric power transformers2008Ingår i: International Journal of Emerging Electric Power Systems, ISSN 2194-5756, E-ISSN 1553-779X, Vol. 9, nr 2Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hot spot temperature (HST) is the most important parameter in the operation of power transformers. The HST has to be held under a prescribed limit. HST has a considerable effect on the insulation aging. Therefore detecting, monitoring and removing the HST could be a very important and necessary action for utilities. A new design of oil spraying and its effect, along with a thermal management in a transformer cooling system has been studied in this paper. The effect of oil fluid flow on the HST problem has been considered in this paper; and the calculations and simulation have been performed by Ants algorithm. The simulation results have been validated based on a 230/63/20 kV, 250MVA transformer at the Sari substation in Iran, and the results indicate that the new design could mitigate the limitations of transformer loading due to the HST problem. The Ants algorithm have been proposed and applied for accomplishing this task and to give an improved level of accuracy.

  • 15.
    Mousavi Takami, Kourosh
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Mahmoudi, Jafar
    Identification of a best thermal formula and model for oil and winding2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    System identification is about building models from data. A data set is characterized by several pieces of information: The input and output signals, the sampling interval, the variable names and units, etc.Similarly, the estimated models contain information of different kinds, estimated parameters, their covariance matrices, and model structure and so on. In this paper we collected Temperature of oil and winding in 230/63kv transformer of SARI Substation and considered the winding temperature for input in the model and oil temperature for out put. After that calculated their data by MATLAB software and get a new model with the good best fit for the heat transfer from core and winding to oil. For verification of were calculated results, has been simulated the process in COMSOL Software.

  • 16.
    Mousavi Takami, Kourosh
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Mahmoudi, Jafar
    Numerical Modelling of Heat Generation and Distribution in the Core and Winding of Power Transformers2008Ingår i: International Journal of Emerging Electric Power Systems, ISSN 1553-779X, Vol. 9, nr 2, s. 1-20Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The power transformer is a complex and critical component of the power transmission and distribution system. System abnormalities, loading, switching and ambient condition normally contribute to accelerated aging and sudden failure. In the absence of critical components monitoring, the failure risk is always high. For early fault detection and real time condition assessment, an online monitoring system in accordance with the age and conditions of the asset would be an important tool. Power loss, heat generation and heat distribution evaluations in a large-scale oil immersed power transformer are presented here, along with the details of computer implementation and experimental verification. Core power losses are approximately constant with temperature variation or may decrease with that. Over the temperature range of 20 to 100°C the change in hysteresis loss Ph with temperature was negligible. Since the total core loss PT decreased with increasing temperature over this range, almost all the loss reduction was due to a reduction in the eddy current loss component Pe that was inversely proportional to the resistivity. Winding and oil temperature will increase with the load increasing and may create a hot spot. This is caused by degradation insulation and the loss of life in the power transformer. Hottest spot temperature and temperature profiles in radial and height coordinates were found using three different methods in this paper. The finite element method (FEM), finite difference method (FDM) and discrete furrier transform methods (DFT) are used to analyze algorithms in this paper. Computational results based on theoretical considerations and using the DFT method are shown to be in good agreement with FDM and FEM. Two mathematical formulae are proposed for temperature distribution in both radial and horizontal axes of core and windings. COMSOL for FEM, GEMINI for FDM and MATLAB for DFT are used.

  • 17.
    Mousavi Takami, Kourosh
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Mahmoudi, Jafar
    Numerical modelling of heat generation and distribution in the core and winding of power transformers2008Ingår i: International Journal of Emerging Electric Power Systems, ISSN 2194-5756, E-ISSN 1553-779X, Vol. 9, nr 2, s. article number: 7-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The power transformer is a complex and critical component of the power transmission and distribution system. System abnormalities, loading, switching and ambient condition normally contribute to accelerated aging and sudden failure. In the absence of critical components monitoring, the failure risk is always high. For early fault detection and real time condition assessment, an online monitoring system in accordance with the age and conditions of the asset would be an important tool. Power loss, heat generation and heat distribution evaluations in a large-scale oil immersed power transformer are presented here, along with the details of computer implementation and experimental verification. Core power losses are approximately constant with temperature variation or may decrease with that. Over the temperature range of 20 to 100°C the change in hysteresis loss Ph with temperature was negligible. Since the total core loss PT decreased with increasing temperature over this range, almost all the loss reduction was due to a reduction in the eddy current loss component Pe that was inversely proportional to the resistivity. Winding and oil temperature will increase with the load increasing and may create a hot spot. This is caused by degradation insulation and the loss of life in the power transformer. Hottest spot temperature and temperature profiles in radial and height coordinates were found using three different methods in this paper. The finite element method (FEM), finite difference method (FDM) and discrete furrier transform methods (DFT) are used to analyze algorithms in this paper. Computational results based on theoretical considerations and using the DFT method are shown to be in good agreement with FDM and FEM. Two mathematical formulae are proposed for temperature distribution in both radial and horizontal axes of core and windings. COMSOL for FEM, GEMINI for FDM and MATLAB for DFT are used. 

  • 18.
    Mousavi Takami, Kourosh
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Mahmoudi, Jafar
    Simulation and optimization of high power super heater reflectors2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    Super heater elements concentrated in very high and clean power at temperature up to 1800 ºc is needed for aluminium melting, oil drying equipment using for power transformers and same that material. There fore, always it is need to minimize power consumption and increase effectiveness at power reflector customers. This means to minimize heat losses in the High Power Reflector, and to optimize heat performance with respect to output power and temperature distribution. This can be done by altering the size and form of the insulating ceramic fiber to have as much power as possible 'reflected' out from the module. It can also be done by altering the size and form of the element .It has been done and the task solved mainly by heat transfer simulations, using COMSOL and MTLAB software’s. To minimize the number of different designs (and thus the number of calculations) were studied; it is also done that statistical methods for experimental design used to determine which designs should be used in the calculations. When an optimal solution has been found, it has been tested at factory’s facilities, with two reference designs.

  • 19.
    Mousavi Takami, Kourosh
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Mahmoudi, Jafar
    Simulation of a novel copper heat Sink using copper pipe and AM method for CPU group heat removing in power transformer’s cabinet2007Ingår i: Proceedings of the Electronic Packaging Technology Conference, EPTC, IEEE , 2007, s. Article number 4441469-Konferensbidrag (Refereegranskat)
    Abstract [en]

    Heat sinks operate by conducting heat from the processor to the heat sink and then radiating it to the air. The better the transfer of heat between the two surfaces (the CPU and the heat sink metal) the better the cooling. Some processors come with heat sinks glued to them directly, ensuring a good transfer of heat between the processor and the heat sink. In this paper author have simulated a new copper heat sink and heat pipe (is a simple device that can quickly transfer heat from one point to another) that has a best heat transferring. A three Dimensional finite element is used for simulations of temperature behaviour on around of heat sink. Analytically approach is applied to determine of heat transfer coefficients. The method has a good convergence and is adaptive with other best designed heat sinks. And so we examine the use of activity migration which reduces peak junction temperature by moving computation between multiple replicated units.

  • 20.
    Mousavi Takami, Kourosh
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Mahmoudi, Jafar
    Thermal evaluation and energy saving with loss reduction in core and winding of power transformers2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    A power loss, heat generation and heat distribution evaluations in a large-scale oil cooled power transformer are presented here, along with the details of computer implementation and experimental verification. In this paper, we consider that core power losses are approximately constant with temperature various or might decreased with that. Winding temperature and oil will increase with the load increasing and might create a hot spot and that is caused by degradation insulation and the loss of life in the power transformer. Therefore the authors tried to Asses these phenomena with use of electrical and thermal soft wares. On the results (with Iranian network data) of simulation showed that in case of oil spraying on the hotspot point or area, very low temperature with the best conditions would be obtained. Then it is best to provide a cooling system with the best insulation and with the minimum side effect on the magnetic and electrical field distribution. Finally by reduction in transformer losses, could savings potential of 22 TWh / year for EU.

  • 21.
    Mousavi Takami, Kourosh
    et al.
    Mälardalens högskola, Institutionen för samhällsteknik.
    Mahmoudi, Jafar
    Mälardalens högskola, Institutionen för samhällsteknik.
    Dahlquist, Erik
    Mälardalens högskola, Institutionen för samhällsteknik.
    Process control in steel core production to reduce of power losses in electrical machines and transformers: Process Control2009Ingår i: Proceedings MATHMOD 09 Vienna, Vienna- Austria: Mathematical Modelling (MATHMOD) 2009 , 2009Konferensbidrag (Refereegranskat)
    Abstract [en]

    The main aim of cold rolling is reduction of strips to the desired final thickness. As the cold rolled strip is being manufactured from hot rolled strip, the uniformity of width, thickness, hardness, etc. are all now intended for improvement.  To reach to this target, need to abound control system to reach the higher quality of slabs.  It should satisfy the several factors, as regards geometrical, mechanical, chemical and surface properties.

    Process control has taken advantage of new measurement equipments, new control actuators and algorithms. Automation and automatic process control can advance the quality further than what is achievable by manual control. This is an important desideration in rolling industry that rolling of slabs needs advanced and optimized process control to increase the productivity and reduction of the variations in the final properties.

    A typical cold rolling stand performs one step in a chain of processes in the cold rolling mill, which can include pickling, rolling, annealing, temper rolling and downstream processes. All these processes contribute to the final properties of the strips. When the main process or the main objective is well controlled, it is important to continue with the other processes. In continuous annealing furnaces, the temperature controls the mechanical properties, but temperature differences and bending around rollers change the flatness. Temper rolling needs the same flatness control as other cold rolling processes. Cooling and lubrication can affect several properties of the strips.

    Precise general control of the strip in a cold steel rolling mill will be discussed in this article.

    Typically, the rolling process is modelled with numerical techniques. But these are not appropriate for a controller design, because they are too difficult. Thus, a linear mathematical model for the rolling process is presented here, which describes the interaction of the required influencing parameters. The attempt leads to numerically professional algorithms, which are essential to run in a real-time situation. With the help of these linear descriptions, the vital elements for the control are investigated. Modern rolling mills are equipped with a servo-hydraulic gap adjustment system, eccentricity control of the rolls, thickness, speed, force and tension controls.

    A model to optimize of the control design process and increasing of accuracy is presented. In this way using the process transfer function in system at different control mode like to thickness, flatness, shape and etc designed a PID and PI optimized controller with using of the best optimization method, final properties increased. The measurements are used to verify the model approach and to detect the most significant sources of disturbances.

    A new linearised numerical model for the rolling process which is suitable for closed loop control has been developed. The model is based on the calculation of the operating point using an available numerical method, followed by determining the partial derivatives at the operating point with respect to all input parameters. Finally, the partial derivatives are combined using superposition to describe the behaviour of the complete system. In this manner, the changes in the output parameters can be determined for small changes in the input parameters. This calculation is numerically efficient and suitable for use in closed loop control.

    Moreover, the roll eccentricity problem and the possibilities to perform compensation will be explained here. Due to the great variety of solutions, a classification of the methods will be sketched. The basic properties of these classes are discussed. Then, a special solution is presented, which has proved its worth already in a practical application. The investigation of its properties is proposed to be typical for the every class, to which the method belongs.

    Finally measurement data which can be used to verify the new model will be performed. The model has been incorporated as a simulation system developed by the authors who enable the simulation of a multi-pass single stand rolling process. To get practical information about the rolling process, a data logging system was developed and installed in Sura AB for data collection.

  • 22.
    Mousavi Takami, Kourosh
    et al.
    Mälardalens högskola, Institutionen för samhällsteknik.
    Mahmoudi, Jafar
    Mälardalens högskola, Institutionen för samhällsteknik.
    Dahlquist, Erik
    Mälardalens högskola, Institutionen för samhällsteknik.
    Lindenmo, Magnus
    Surahammars Bruks AB, R&D.
    Evaluation of magnetic aging in transformers and electrical machines cores during operation: Modelling2009Ingår i: Proceedings of the Scientific Conference on Energy and IT at Älvsjö fair, Stockholm March 11-12, 2009 in connection with the “Energitinget 2009, 2009, s. 218-232Konferensbidrag (Refereegranskat)
    Abstract [en]

    Electric steels are processed to avoid the phenomenon known as magnetic aging. Non-oriented electrical steels are mostly used in rotating electrical machines and oriented steels used in transformers, which during operation generates heat. This could cause carbide precipitation/coalescence in the metallic matrix, impairing the magnetic properties of the steel, called magnetic aging. The steel has to contain very little carbon to avoid aging. This is achieved during the making of the steel or by a decarburising annealing of the final thickness strip or of the stamped laminations.

    The magnetic material for cores of a transformer and electrical machines should be characterised by high permeability and low energy losses in changing magnetic flux.

    In order to test that the magnetic properties do not become worse during these working conditions, the steel can be tested for magnetic ageing. The European standard defines the test cycle as 225°C for 24 hours. The American ASTM standard suggests two different cycles: 100 hours at 150°C or 600 hours at 100 °C.

     

    A test the losses after a heat treatment of 150°C f or 10 days for coils with higher carbon content than 26 ppm of the final product has performed here. This longer cycle has proved to give larger increases in the loss than the shorter one according to the European standard.

    The ageing process was much faster for a higher carbon content slab with 90 ppm C than for a lower one with 30 ppm C.

    ANN method using LMS has performed to aging real time identification. Results showed a 97% best fit. It showed that using ANN can predict the aging and a modern advanced relay can control the loading and temperature of electrical equipments to prevent of harmful damages.

  • 23.
    Mousavi Takami, Kourosh
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Mahmoudi, Jafar
    Gholinejad, Hasan
    Evaluation of Large Power Transformer Losses for green house gas and final cost reductions2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    Transformers are more complex devices, consisting of an iron core around which are wrapped various coils of insulated wires, inside a tank filled with insulating oil, along with connectors, bushings and various other small components. Overloading causes excess heat in a transformer, the negative effects of which are degradation of the kraft paper insulation around the wires (leading to internal failures of the coils), excessive tank pressure or degradation of the insulating oil (either of which can cause catastrophic failures, even explosions), and leaking gaskets and seals. (Since the copper used in the windings is already soft (annealed) and is not under tension, overheating of the conductors is generally not a concern.) Thermal cycling contributes to mechanical damage by loosening connections. Because of hysteresis in the transformer core, overloading generates harmonics and these can cause mechanical vibration of the transformer, contributing to physical damage. Overloading also assumes that faults near the transformer, when they occur, will be greater than normal, so there is the increased likelihood of damage to the transformer from fault currents; such damage can be manifested by coil failures, bushing flashovers, blown gaskets and seals, connector failures, oil explosions and fires, and physical displacement of internal components due to electromechanical torques. In the world consume millions barrels oils for cover of electrical losses then produced green house gas. With introduce of new method for loss reduction authors find a new method that presented in this paper. In this paper we Asses the impact of losses on final cost of transformer and so green house gas. And would proved that losses cost is equal of capital investment for buying a transformer. Emissions of in electrical network is 0.4 kg / kWh, that for the world only for transformer losses are (11,500 billion kilowatts hours are produced electricity) closed to 46 billion tons and can reduce it to 23 billion ton by a good looses management.

  • 24.
    Mousavi Takami, Kourosh
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Mahmoudi, Kourosh
    A novel study on the power transformer losses in relation to CO2 capturing technology2008Ingår i: International journal of energy research (Print), ISSN 0363-907X, E-ISSN 1099-114X, Vol. 32, nr 12, s. 1151-1163Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Transformers are complex devices consisting of an iron core around which are wrapped various coils of insulated wires, inside a tank filled with insulating oil, along with connectors, bushings and various other small components. Overloading causes excess heat in a transformer, the negative effects of which are degradation of the kraft paper insulation around the wires (leading to internal failures of the coils), excessive tank pressure or degradation of the insulating oil (either of which can cause catastrophic failures, even explosions), and leaking gaskets and seals. (Since the copper used in the windings is already soft (annealed) and is not under tension, overheating of the conductors is generally not a concern.) Thermal cycling contributes to mechanical damage by loosening connections. Because of hysteresis in the transformer core, overloading generates harmonics and these can cause mechanical vibration of the transformer, contributing to physical damage. Overloading also assumes that faults near the transformer, when they occur, will be greater than normal, so there is the increased likelihood of damage to the transformer from fault currents; such damage can be manifested by coil failures, bushing flashovers, blown gaskets and seals, connector failures, oil explosions and fires, and physical displacement of internal components due to electromechanical torques. In addition, the world consumes millions of barrels of oils to cover the electrical losses, which then produces green house gases. With the introduction of new method for loss reduction, authors found a new method that is presented in this paper. In this paper we assess the impact of losses on final cost of transformer and green house gases. It is proved that losses cost is equal to the capital investment of the transformer. Emissions of CO2 in the electrical network is 0.4 kg CO2 kWh-1, which is (11 500 billion kilowatts hours of electricity produced) around 46 billion tons of transformer losses. This can be reduced to 23 billion ton using loss management. It is obvious that to cover losses generation of extra electricity is needed. Extra production leads to more CO2 emission. Installation of CO2 capturing device utilities at least can prevent more pollution emissions. For these reasons, a CO2 capturing condenser applicable in power station is presented here. It was simulated using COMSOL software. Copyright © 2008 John Wiley & Sons, Ltd.

  • 25.
    Mousavi Takami, Kourosh
    et al.
    Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling.
    Mousavi Takami, Seyyed Mohammad Esmail
    Simulation of energy in the building and design a new intelligent2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    Building energy simulation is important for the studyof energy efficiency in buildings. An energy saving control system of lightning, heating and variable-airvolume air conditioner in intelligence building is simulated in this paper. It reaches good control effect and energy efficiency by making the best of the advantages of intelligence building. In the regulating period, the lightning lux, heating flux and air volume is decided by means of feed forward control. The previous turning off period is determined in the way of penalty function. It has been used in a sample building for developing building energy standards and analysing energy consumption and conservation measures of buildings.

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