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## Ðề: Inrush current in transformer

**"inrush current in transformer" thuộc dòng điện xung kích Khi đóng MBA không cài đặt vào lưới năng lượng điện, vào quy trình quá đáng này cái năng lượng điện này đã không hề nhỏ cùng gồm những thành phần sóng hàicòn về cụ thể thì bạn đọc sách nhé**

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**chúng ta cũng có thể chỉ ra rằng cho doanh nghiệp mối cung cấp tài liệu cơ mà bạn tham khảo về sự việc này không?tôi đã đọc nhiều tài liệu giờ Việt cơ mà không thấy tài liệu nào nói chuyên sâu về vụ việc này không còn.Tài liệu tiếng Anh thì bản thân kiếm được bên trên mạng dẫu vậy không có gì bảo vệ là an toàn.Tài liệu tin cậy nhất là các bài báo của IEEE cơ mà bắt buộc tốn 10$ mới down được bài xích.Thanks chúng ta trước !!!!!!!!!!!!!!!!!**

**tôi bao gồm một số trong những tài liệu giờ đồng hồ Anh của một ông TS Iran nè:Nhưng gọi hoài thiếu hiểu biết, trên bởi vì câu chữ của nó nói hết sức giống văn bản nói đến chiếc năng lượng điện từ bỏ hóa: bạn gồm hiểu Theo phong cách như thế nào xin chỉ giáo cho. Nội dung nlỗi sau: ELECTRONICS AND ELECTRICAL ENGINEERING ISSN 1392 – 1215 2011. No. 3(109) ELEKTRONIKA IR ELEKTROTECHNIKA ELECTRICAL ENGINEERING T 190 ────────────────� �──── ELEKTROS INŽINERIJACalculation & Analysis of Transformer Inrush Current Based onParameters of Transformer and Operating ConditionsM. Jamali, M. Mirzaie, S. Asghar GholamianDepartment of Electrical and Computer Engineering, Babol University of Technology,P. O. Box. 484, Shariaty Ave sầu., Babol, Iran, phone: +981113239214, e-mail: m.jamali**

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stu.nit.ac.ir energizing circuit impedance và remanent flux on theIntroduction characteristics of inrush current are investigated in detail. Magnetizing inrush current in transformers resultsfrom any abrupt changes of the magnetizing voltage. This Fundamentals of Inrush Currentcurrent in transformer may be caused by energizing an It is very well known that a transformer willunloaded transformer, occurrence of an external fault, experience magnetizing inrush current during energization.voltage recovery after clearing an external fault and out-of- Inrush current occurs in a transformer whenever thephase synchronizing of connected generator <1-2>. Because residual flux does not match the instantaneous value of thethe amplitude of inrush current can be as high as a short- steady-state flux which would normally be required for thecircuit current, a detailed analysis of the magnetizing particular point on the voltage wavekhung at which theinrush current under various conditions is necessary for the circuit is closed <13>.concerns of a protective system for the transformers. In For the explanation of the mechanism causing inrushthis regard, some numerical và analytical methods have sầu current in a transformer’s primary winding whenbeen proposed in the literature. In <3>, analytical connected to an AC voltage source, we consider (1), whereexpressions for the magnetic fluxes of no-load three-phase λ và v are the instantaneous flux in a transformer core andtransformer is presented that can be used for inrush current voltage drop across the primary winding, respectivelycalculation. In <4>, by analytical solution of two differentialequations that governs the behavior of a transformer, the (1) .magnetic flux và inrush current are determined. Formodeling transformer core including hysteresis, <5> used As we see from (1), the rate of change ofJiles-Atherton theory & presented a new algorithm on a instantaneous flux in a transformer core is proportional tosample transformer. In <6>, an analytic formula is presented the instantaneous voltage drop in the primary winding orkhổng lồ calculate the peak inrush current of a nonlinear inductor on the other hand, the flux waveform is the integral of thewith a series resistor. In <7>, a simple mã sản phẩm for the voltage waveform. In continuously-operating transformer,transient period of inrush current is presented. This Mã Sản Phẩm these two waveforms are shifted by 90°. But a significantis developed from the structural parameters of transformer. difference exists between continuous-mode operation andTo avoid malfunctiom of protection system under energization of a transformer. During continuousmagnetizing inrush current, many researches are conducted operation, the flux level is at its negative sầu peak whenfor the discrimination of inrush current from internal fault voltage is at its zero point, but during energization the fluxcurrents. For example, in <8-10>, inrush current are has to lớn start at zero. So, for a rising voltage just started fromdiscriminated from internal fault current by second zero, the magnetic flux will reach approximately twice itsharmonic criterion. For discrimination of these currents, normal peak as it integrates the area under the voltage<11> used the sum of active power flowing inkhổng lồ the waveform’s first half-cycle. This amount of flux, becausetransformer from each terminal. In <12>, a criterion of the nonlinear characteristic of the magnetization curve sầu,function in terms of difference of amplitude of wavelet causes saturation of the transformer. During saturation,coefficients is defined. Then by using this criterion disproportionate amounts of mmf are needed lớn generatefunction for three phases, the internal faults are magnetic flux. This means the winding current, whichdiscriminated from the inrush current. creates the mmf to cause flux in the core, will In this paper, first, the fundamentals of inrush current disproportionately rise to a value easily exceeding twice itsand the formulas that are used for calculation it, are normal peak. Fig. 1 shows the generation of inrush currentpresented. Then a one-phase transformer is simulated in in a transformer. As seen from the figure, exceeding fluxMATLAB and the effects of switching angle variation, 17 with those parameters are presented in <4>, is selected. Thefrom the knee point, results in large magnetizing current parameters of the equivalent circuit of this transformerthat in some circumstances can be ten times of the rated referred to the 220V winding are shown in Table 1.current in a transformer. Fig. 2. Equivalent circuit of the transformer under no load Table 1. Parameters of the simulated transformerFig. 1. Generation of inrush current in a transformer Rs (Ω) Ls (mH) Rp (Ω) Parameter The general equation that gives the amplitude of 15.476 12 7260 Valueinrush current as a function of time can be expressed as Also, the magnetization curve of the transformer is(2): given in (4) where i và λ are magnetizing current & flux respectively √ . , (2)where Vm – maximum applied voltage; Zt – total impedance sinc 2.43 . 63.084 10 (4)under inrush, including system; φ – energization angle; t –time; t0 – point at which core saturates; τ – time constant of It should be noted that equations (5)-(8) are used totransformer winding under inrush conditions; α – function calculate the fundamental & second harmonicof t0; Kw – accounts for 3 phase winding connection; Ks – components of inrush current, where N, T & f are numberaccounts for short-circuit power of network. of samples in each cycle, period & frequency of the For the purpose of designing a protective sầu system for power system, respectively. Also, m indicates fundamentaltransformer, the peak value of inrush current is an và second components with the numbers 1 và 2,important factor. In these cases, a simplified equation can respectively. The sampling rate of 30 kHz has been used inbe used to lớn calculate the peak value of the first cycle of the this paper:inrush current. This equation is as follow 2 2. √2 . cos .2 . , (3) (5) , .where Vm – maximum applied voltage; L – air coreinductance of the transformer; R – total dc resistance of the 2 . sin .2 . , (6)transformer; BN – normal rated flux density of thetransformer core; BR – remanent flux density of thetransformer core; BS – saturation flux mật độ trùng lặp từ khóa of the corematerial. (7) , As seen from the equations (2) và (3), the value ofinrush current is dependent to lớn the parameters oftransformer và operating conditions. So a detailed %2 100. (8)analysis for finding the relations between the inrushcurrent characteristics và these factors are needed. Effects of switching angleSimulation results In this section, the effect of switching angle variation When a transformer is energized under no load or on the characteristics of inrush current has beenlightly loaded conditions, inrush current may flow in the investigated. The remanent flux (Br) for all switchingprimary circuit. In this situation, the equivalent circuit of angles is 0.826 Wb-coil. Also the source resistance hastransformer can be shown as Fig. 2 where Rs, Ls, Rp, Lm been considered to zero. Fig. 3 shows the effect ofvà Rt are series resistance, series inductance, core losses different switching angles (θ) on the amplitude of inrushresistance, magnetizing inductance & source resistance current. As seen from the figure, the highest amplitude ofrespectively. inrush current is at 0 ̊ that is 5.52A. Also, it can be seen, In order to investigate the effects of some parameters increasing of the switching angle will decrease theof transformer or network on the inrush current of a typical amplitude of inrush current.transformer, a 120 VA, 60 Hz, (220/120) V transformer 18 inrush current. Also, it causes faster decay in the amplitude of inrush current. Therefore, it can be said that transformers located closer to the generating plants display higher amount of inrush currents lasting much longer than transformer installed electrically away from generator.Fig. 3. Effect of switching angle variation on the amplitude ofinrush current The second harmonic content of inrush current isshown in Fig. 4. As seen from this figure, increasing of theswitching angle causes to lớn a decrease in the percentage Fig. 5. Effect of source resistance on the amplitude of inrushsecond harmonic. current The effect of source resistance in the percentage of second harmonic has been shown in Fig. 6. The results show that the amount of percentage of second harmonic will be decreased by increasing the source resistance.Fig. 4. Effect of switching angles in the percentage secondharmonic It should be noted that, although, the highestamplitude of the inrush current appears in the first cycle& then decays, but the highest percentage second Fig. 6. Effect of source resistance in the percentage secondharmonic does not necessarily appear in the first cycle. For harmonicinstance as seen from Fig. 3 và Fig. 4, at θ=90 ̊, bothamplitude và percentage second harmonic have sầu been Effects of the remanent fluxdecreased with increasing cycle, but at θ=0 ̊, although theamplitude of inrush current have sầu been decreased, but The effect of remanent flux on the first cycle peaksecond harmonic firstly increased và then decreased. This current at different switching angles is shown in Fig. 7. Asis important when using second harmonic content lớn seen from figure, the first cycle peak current has largerestrain the relay operation during magnetizing inrush change when the remanent flux varies. Also the resultsconditions. indicate that switching at θ=90 ̊ or Br=0 may not necessarily reduce the magnitude of inrush current. So, forEffects of source resistance reducing inrush current, an appropriate switching angle by considering remanent flux must be selected. In this case, the switching angle (θ) is 0 ̊. Also, theremanent flux (Br) is the same as the previous section. The Conclusionseffects of source resistance have been considered byincreasing Rt. Fig. 5 shows the effect of source resistance In this paper, the effects of some parameters on theon the amplitude of inrush current. As seen from figure, characteristics of inrush current are investigated inincreasing source resistance will decrease the amplitude of MATLAB Simulinks. 19 4. Vanti M. G., Bertoli S. L. Semianalytic solution for a simple model of inrush currents in transformers // IEEE Trans. Magnetics. – June, 2008. – Vol. 44. – No. 6. – P.. 1270–1273. 5. Vahidi B., Tavakoli M. R. B. An algorithm for evaluating inrush current in transformers using Jiles–Atherton theory of ferromagnetic hysteresis // IEEE Conf. Tencon, Hong Kong. – November, 2006. – P. 1–4. 6. Wang Y., Abdulsalam S. G., Xu W. Analytical formula khổng lồ estimate the maximum inrush current // IEEE Trans. nguồn Delivery. – April, 2008. – Vol. 23. – No. 2. – P. 1266–1268. 7. Chen S. D., Lin R. L. Magnetizing inrush Model of transformers based on structure parameters // IEEE Trans. nguồn Delivery. – July, 2005. – Vol. đôi mươi. – No. 3. – P.. 1947– 1954. 8. Sykes J. A., Morrison I. F. A proposed method of harmonic restraint differential protecting of transformers by digital computer // IEEE Trans. nguồn App. Systems. – May, 1972.Fig. 7. Effect of remanent flux on first cycle peak current – Vol. PAS–91. – No. 3. – P.. 1266–1272. 9. Kasztenny B., Kulidjian A. An improved transformer inrush Results show that increasing switching angle at a restraint algorithm increases security while maintaining faultpositive sầu remanent flux or source resistance will decrease response performance // 53rd Annual Conference forthe amplitude of inrush current. It has been shown that Protective Relay Engineers. – April, 2000. –P. 1–27.largest second harmonic nội dung may not necessarily 10. Wang J. Hamilton R. Analysis of transformer inrush currentappear at the first cycle. The effect of remanent flux on the and comparison of harmonic restraint methods infirst cycle peak current shows that it has large changes transformers protection // 61st Annual Conference forwhen the remanent flux varies. Also, it has been concluded Protective sầu Relay Engineers. – April, 2008. – P. 142–169. 11. Yabe K. Power differential method for discriminationthat for reducing inrush current, an appropriate switching between fault & magnetizing inrush current in transformersangle by considering remanent flux, must be selected. // IEEE Trans. nguồn Delivery. – July, 1997. – Vol. 12. – No. 3. – Phường. 1109–1118.References 12. Faiz J. Lotfi–Fard S. A novel wavelet–based algorithm for discrimination of internal faults from magnetizing inrush1. Blume L. F. Transformer Engineering. – New York: Wiley currents in power transformers // IEEE Trans. Power & Sons, 1951. Delivery. – October, 2006. – Vol. 21. – No. 4. – P. 1989–2. Karkhông nên K., Kerenyi D. and Kiss L. Large power 1996. transformers. – New York: Elsevier, 1987. 13. Sonnemann W. K., Wagner C. L., Rockefeller G. D.3. L. Andriušienė, Phường. Kostrauskas, D. Mikalajūnas. Magnetizing Inrush Phenomena in Transformer Banks // Determination of the Magnetic Fluxes of No–Load Three– AIEE Transaction. – October, 1958. – Part III. – Vol. 77. – P. Phase Power Transformer // Electronics & Electrical 884–892. Engineering. – Kaunas: Technologija, 2003. – No. 2(44). – P.. 43–47. Received 2010 07 04M. Jamali, M. Mirzaie, S. Asghar Gholamian. Calculation and Analysis of Transformer Inrush Current Based on Parametersof Transformer và Operating Conditions // Electronics và Electrical Engineering. – Kaunas: Technologija, 2011. – No. 3(109).– P. 17–đôi mươi. An inrush current is a transient current with high amplitude that may occur when a transformer is energized under no load or lightlyloaded conditions. The magnitude of inrush current may be as high as ten times or more times of transformer rated current. This couldresult in huge mechanical và thermal stresses on transformer in addition to inadvertent operation of the protective sầu relay systems. Thispaper represents the effects of some factors on the inrush current of transformers. For this purpose, a one-phase transformer is simulatedin MATLAB & the effects of switching angle variation, the energizing circuit impedance và the remanent flux on the characteristicsof inrush current are investigated. The results show that increasing circuit resistance or switching angle will decrease inrush currentamplitude. Also, it is concluded that for reducing inrush current, appropriate switching angle with respect to the remanent flux must beselected. The results can be used for a better understanding of the inrush current characteristics and proper actions of the protectivesystem. Ill. 7, bibl. 13, tabl. 1 (in English; abstracts in English và Lithuanian).M. Jamali, M. Mirzaie, S. Asghar Gholamian. Transformatoriaus parametrų ir darbo sąlygų įtakos transformatoriausįmagnetinimo srovei apskaičiavimas ir tyrimas // Elektronika ir elektrotechnika. – Kaunas: Technologija, 2011. – Nr. 3(109). –Phường. 17–20. Įmagnetinimo srovė yra didelės amplitudės momentinė srovė, kuri gali atsirasti, kai transformatorius susižadimãng cầu, kai nėra jokiosapkrovos artía kai ji maža. Įmagnetinimo srovė gali būti daugiau nei dešimt kartų didesnė už nominalią vertę. Toks poveikis, atsiradęsdėl mechaninių ir terminių procesų, neigiamai veitê reles. Aprašongươi veiksniai, turintys įtakos įmagnetinimo srovei. Atliktas vienfaziotransformatoriaus modeliavimas programų paketu Matlab, įvertinti pagrindiniai parametrai. Il. 7, bibl. 13, lent. 1 (anglų kalba;santraukos anglų ir lietuvių k.). 20

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stu.nit.ac.ir energizing circuit impedance và remanent flux on theIntroduction characteristics of inrush current are investigated in detail. Magnetizing inrush current in transformers resultsfrom any abrupt changes of the magnetizing voltage. This Fundamentals of Inrush Currentcurrent in transformer may be caused by energizing an It is very well known that a transformer willunloaded transformer, occurrence of an external fault, experience magnetizing inrush current during energization.voltage recovery after clearing an external fault and out-of- Inrush current occurs in a transformer whenever thephase synchronizing of connected generator <1-2>. Because residual flux does not match the instantaneous value of thethe amplitude of inrush current can be as high as a short- steady-state flux which would normally be required for thecircuit current, a detailed analysis of the magnetizing particular point on the voltage wavekhung at which theinrush current under various conditions is necessary for the circuit is closed <13>.concerns of a protective system for the transformers. In For the explanation of the mechanism causing inrushthis regard, some numerical và analytical methods have sầu current in a transformer’s primary winding whenbeen proposed in the literature. In <3>, analytical connected to an AC voltage source, we consider (1), whereexpressions for the magnetic fluxes of no-load three-phase λ và v are the instantaneous flux in a transformer core andtransformer is presented that can be used for inrush current voltage drop across the primary winding, respectivelycalculation. In <4>, by analytical solution of two differentialequations that governs the behavior of a transformer, the (1) .magnetic flux và inrush current are determined. Formodeling transformer core including hysteresis, <5> used As we see from (1), the rate of change ofJiles-Atherton theory & presented a new algorithm on a instantaneous flux in a transformer core is proportional tosample transformer. In <6>, an analytic formula is presented the instantaneous voltage drop in the primary winding orkhổng lồ calculate the peak inrush current of a nonlinear inductor on the other hand, the flux waveform is the integral of thewith a series resistor. In <7>, a simple mã sản phẩm for the voltage waveform. In continuously-operating transformer,transient period of inrush current is presented. This Mã Sản Phẩm these two waveforms are shifted by 90°. But a significantis developed from the structural parameters of transformer. difference exists between continuous-mode operation andTo avoid malfunctiom of protection system under energization of a transformer. During continuousmagnetizing inrush current, many researches are conducted operation, the flux level is at its negative sầu peak whenfor the discrimination of inrush current from internal fault voltage is at its zero point, but during energization the fluxcurrents. For example, in <8-10>, inrush current are has to lớn start at zero. So, for a rising voltage just started fromdiscriminated from internal fault current by second zero, the magnetic flux will reach approximately twice itsharmonic criterion. For discrimination of these currents, normal peak as it integrates the area under the voltage<11> used the sum of active power flowing inkhổng lồ the waveform’s first half-cycle. This amount of flux, becausetransformer from each terminal. In <12>, a criterion of the nonlinear characteristic of the magnetization curve sầu,function in terms of difference of amplitude of wavelet causes saturation of the transformer. During saturation,coefficients is defined. Then by using this criterion disproportionate amounts of mmf are needed lớn generatefunction for three phases, the internal faults are magnetic flux. This means the winding current, whichdiscriminated from the inrush current. creates the mmf to cause flux in the core, will In this paper, first, the fundamentals of inrush current disproportionately rise to a value easily exceeding twice itsand the formulas that are used for calculation it, are normal peak. Fig. 1 shows the generation of inrush currentpresented. Then a one-phase transformer is simulated in in a transformer. As seen from the figure, exceeding fluxMATLAB and the effects of switching angle variation, 17 with those parameters are presented in <4>, is selected. Thefrom the knee point, results in large magnetizing current parameters of the equivalent circuit of this transformerthat in some circumstances can be ten times of the rated referred to the 220V winding are shown in Table 1.current in a transformer. Fig. 2. Equivalent circuit of the transformer under no load Table 1. Parameters of the simulated transformerFig. 1. Generation of inrush current in a transformer Rs (Ω) Ls (mH) Rp (Ω) Parameter The general equation that gives the amplitude of 15.476 12 7260 Valueinrush current as a function of time can be expressed as Also, the magnetization curve of the transformer is(2): given in (4) where i và λ are magnetizing current & flux respectively √ . , (2)where Vm – maximum applied voltage; Zt – total impedance sinc 2.43 . 63.084 10 (4)under inrush, including system; φ – energization angle; t –time; t0 – point at which core saturates; τ – time constant of It should be noted that equations (5)-(8) are used totransformer winding under inrush conditions; α – function calculate the fundamental & second harmonicof t0; Kw – accounts for 3 phase winding connection; Ks – components of inrush current, where N, T & f are numberaccounts for short-circuit power of network. of samples in each cycle, period & frequency of the For the purpose of designing a protective sầu system for power system, respectively. Also, m indicates fundamentaltransformer, the peak value of inrush current is an và second components with the numbers 1 và 2,important factor. In these cases, a simplified equation can respectively. The sampling rate of 30 kHz has been used inbe used to lớn calculate the peak value of the first cycle of the this paper:inrush current. This equation is as follow 2 2. √2 . cos .2 . , (3) (5) , .where Vm – maximum applied voltage; L – air coreinductance of the transformer; R – total dc resistance of the 2 . sin .2 . , (6)transformer; BN – normal rated flux density of thetransformer core; BR – remanent flux density of thetransformer core; BS – saturation flux mật độ trùng lặp từ khóa of the corematerial. (7) , As seen from the equations (2) và (3), the value ofinrush current is dependent to lớn the parameters oftransformer và operating conditions. So a detailed %2 100. (8)analysis for finding the relations between the inrushcurrent characteristics và these factors are needed. Effects of switching angleSimulation results In this section, the effect of switching angle variation When a transformer is energized under no load or on the characteristics of inrush current has beenlightly loaded conditions, inrush current may flow in the investigated. The remanent flux (Br) for all switchingprimary circuit. In this situation, the equivalent circuit of angles is 0.826 Wb-coil. Also the source resistance hastransformer can be shown as Fig. 2 where Rs, Ls, Rp, Lm been considered to zero. Fig. 3 shows the effect ofvà Rt are series resistance, series inductance, core losses different switching angles (θ) on the amplitude of inrushresistance, magnetizing inductance & source resistance current. As seen from the figure, the highest amplitude ofrespectively. inrush current is at 0 ̊ that is 5.52A. Also, it can be seen, In order to investigate the effects of some parameters increasing of the switching angle will decrease theof transformer or network on the inrush current of a typical amplitude of inrush current.transformer, a 120 VA, 60 Hz, (220/120) V transformer 18 inrush current. Also, it causes faster decay in the amplitude of inrush current. Therefore, it can be said that transformers located closer to the generating plants display higher amount of inrush currents lasting much longer than transformer installed electrically away from generator.Fig. 3. Effect of switching angle variation on the amplitude ofinrush current The second harmonic content of inrush current isshown in Fig. 4. As seen from this figure, increasing of theswitching angle causes to lớn a decrease in the percentage Fig. 5. Effect of source resistance on the amplitude of inrushsecond harmonic. current The effect of source resistance in the percentage of second harmonic has been shown in Fig. 6. The results show that the amount of percentage of second harmonic will be decreased by increasing the source resistance.Fig. 4. Effect of switching angles in the percentage secondharmonic It should be noted that, although, the highestamplitude of the inrush current appears in the first cycle& then decays, but the highest percentage second Fig. 6. Effect of source resistance in the percentage secondharmonic does not necessarily appear in the first cycle. For harmonicinstance as seen from Fig. 3 và Fig. 4, at θ=90 ̊, bothamplitude và percentage second harmonic have sầu been Effects of the remanent fluxdecreased with increasing cycle, but at θ=0 ̊, although theamplitude of inrush current have sầu been decreased, but The effect of remanent flux on the first cycle peaksecond harmonic firstly increased và then decreased. This current at different switching angles is shown in Fig. 7. Asis important when using second harmonic content lớn seen from figure, the first cycle peak current has largerestrain the relay operation during magnetizing inrush change when the remanent flux varies. Also the resultsconditions. indicate that switching at θ=90 ̊ or Br=0 may not necessarily reduce the magnitude of inrush current. So, forEffects of source resistance reducing inrush current, an appropriate switching angle by considering remanent flux must be selected. In this case, the switching angle (θ) is 0 ̊. Also, theremanent flux (Br) is the same as the previous section. The Conclusionseffects of source resistance have been considered byincreasing Rt. Fig. 5 shows the effect of source resistance In this paper, the effects of some parameters on theon the amplitude of inrush current. As seen from figure, characteristics of inrush current are investigated inincreasing source resistance will decrease the amplitude of MATLAB Simulinks. 19 4. Vanti M. G., Bertoli S. L. Semianalytic solution for a simple model of inrush currents in transformers // IEEE Trans. Magnetics. – June, 2008. – Vol. 44. – No. 6. – P.. 1270–1273. 5. Vahidi B., Tavakoli M. R. B. An algorithm for evaluating inrush current in transformers using Jiles–Atherton theory of ferromagnetic hysteresis // IEEE Conf. Tencon, Hong Kong. – November, 2006. – P. 1–4. 6. Wang Y., Abdulsalam S. G., Xu W. Analytical formula khổng lồ estimate the maximum inrush current // IEEE Trans. nguồn Delivery. – April, 2008. – Vol. 23. – No. 2. – P. 1266–1268. 7. Chen S. D., Lin R. L. Magnetizing inrush Model of transformers based on structure parameters // IEEE Trans. nguồn Delivery. – July, 2005. – Vol. đôi mươi. – No. 3. – P.. 1947– 1954. 8. Sykes J. A., Morrison I. F. A proposed method of harmonic restraint differential protecting of transformers by digital computer // IEEE Trans. nguồn App. Systems. – May, 1972.Fig. 7. Effect of remanent flux on first cycle peak current – Vol. PAS–91. – No. 3. – P.. 1266–1272. 9. Kasztenny B., Kulidjian A. An improved transformer inrush Results show that increasing switching angle at a restraint algorithm increases security while maintaining faultpositive sầu remanent flux or source resistance will decrease response performance // 53rd Annual Conference forthe amplitude of inrush current. It has been shown that Protective Relay Engineers. – April, 2000. –P. 1–27.largest second harmonic nội dung may not necessarily 10. Wang J. Hamilton R. Analysis of transformer inrush currentappear at the first cycle. The effect of remanent flux on the and comparison of harmonic restraint methods infirst cycle peak current shows that it has large changes transformers protection // 61st Annual Conference forwhen the remanent flux varies. Also, it has been concluded Protective sầu Relay Engineers. – April, 2008. – P. 142–169. 11. Yabe K. 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Phase Power Transformer // Electronics & Electrical 884–892. Engineering. – Kaunas: Technologija, 2003. – No. 2(44). – P.. 43–47. Received 2010 07 04M. Jamali, M. Mirzaie, S. Asghar Gholamian. Calculation and Analysis of Transformer Inrush Current Based on Parametersof Transformer và Operating Conditions // Electronics và Electrical Engineering. – Kaunas: Technologija, 2011. – No. 3(109).– P. 17–đôi mươi. An inrush current is a transient current with high amplitude that may occur when a transformer is energized under no load or lightlyloaded conditions. The magnitude of inrush current may be as high as ten times or more times of transformer rated current. This couldresult in huge mechanical và thermal stresses on transformer in addition to inadvertent operation of the protective sầu relay systems. Thispaper represents the effects of some factors on the inrush current of transformers. For this purpose, a one-phase transformer is simulatedin MATLAB & the effects of switching angle variation, the energizing circuit impedance và the remanent flux on the characteristicsof inrush current are investigated. The results show that increasing circuit resistance or switching angle will decrease inrush currentamplitude. Also, it is concluded that for reducing inrush current, appropriate switching angle with respect to the remanent flux must beselected. The results can be used for a better understanding of the inrush current characteristics and proper actions of the protectivesystem. Ill. 7, bibl. 13, tabl. 1 (in English; abstracts in English và Lithuanian).M. Jamali, M. Mirzaie, S. Asghar Gholamian. Transformatoriaus parametrų ir darbo sąlygų įtakos transformatoriausįmagnetinimo srovei apskaičiavimas ir tyrimas // Elektronika ir elektrotechnika. – Kaunas: Technologija, 2011. – Nr. 3(109). –Phường. 17–20. Įmagnetinimo srovė yra didelės amplitudės momentinė srovė, kuri gali atsirasti, kai transformatorius susižadimãng cầu, kai nėra jokiosapkrovos artía kai ji maža. Įmagnetinimo srovė gali būti daugiau nei dešimt kartų didesnė už nominalią vertę. Toks poveikis, atsiradęsdėl mechaninių ir terminių procesų, neigiamai veitê reles. Aprašongươi veiksniai, turintys įtakos įmagnetinimo srovei. Atliktas vienfaziotransformatoriaus modeliavimas programų paketu Matlab, įvertinti pagrindiniai parametrai. Il. 7, bibl. 13, lent. 1 (anglų kalba;santraukos anglų ir lietuvių k.). 20