các yếu tố vĩ mô ảnh hưởng đến chi phí hàng tồn kho
CƠ SỞ LÝ THUYẾT VỀ CHẤT LƯỢNG ĐIỆN (Power Quality Primer)
Ngày tải lên :
14/08/2014, 12:31
... circuit (IC) chips They are the source of this sensitivity, which has increased over the last 25 years as more transistors have been placed on a micro chip The number of transistors on a chip has ... industry has observed that each new chip contains roughly twice as much capacity as its predecessor and each chip is released within 18 to 24 months of the previous chip This principle has become ... made this observation in a 1965 speech As computer chip manufacturers seek to increase the density of electrical components on a chip, the chips become even more sensitive to changes in the electrical...
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AN UPDATE ON POWER QUALITY pptx
Ngày tải lên :
17/03/2014, 02:20
... 26] Here the increase in switching frequency reduces the current harmonics but this makes the switching losses too much Furthermore, we cannot keep on increasing switching frequency because this ... fluctuations other that wind turbine switching operation The second one is regarding the switching operation The voltage and current transients are measured during the switching operation of wind turbine ... proposed [20] PWM is a magical technique of switching that gives unique results by varying the associated parameters like modulation index, switching frequency and the modulation ratio The frequency...
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AN UPDATE ON POWER QUALITY doc
Ngày tải lên :
23/03/2014, 15:20
... 26] Here the increase in switching frequency reduces the current harmonics but this makes the switching losses too much Furthermore, we cannot keep on increasing switching frequency because this ... fluctuations other that wind turbine switching operation The second one is regarding the switching operation The voltage and current transients are measured during the switching operation of wind turbine ... proposed [20] PWM is a magical technique of switching that gives unique results by varying the associated parameters like modulation index, switching frequency and the modulation ratio The frequency...
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Power Quality Harmonics Analysis and Real Measurements Data Part 15 doc
Ngày tải lên :
18/06/2014, 22:20
... FFT analysis for this waveform is shown It is observed that the harmonics components near the switching frequency are considerably higher than the fundamental component Harmonics components 70 (3500 ... 271 harmonic 70 has a magnitude of 17.54 V, as shown in Fig 9a Moreover, the multiples of the switching frequencies are also considerable respect to the fundamental component, as shown in Fig 9b, ... Consistently with the voltage waveform, the dominant harmonic component in the ground current fits the switching frequency of the converter That is harmonic component 68 with 503% of the fundamental component...
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Power Quality Harmonics Analysis and Real Measurements Data Part 1 pdf
Ngày tải lên :
19/06/2014, 08:20
... ripples in the voltage waveform of rotating machines Variations in air-gap reluctance over synchronous machine pole pitch Flux distortion in the synchronous machine from sudden load changes Non-sinusoidal ... conservation measures, such as those for improved motor efficiency and load matching, which employ power semiconductor devices and switching for their operation These devices often produce irregular voltage ... mis-operation of systems which accomplish remote switching, load control, and metering Excessive losses in – and heating of – induction and synchronous machines Over voltages and excessive currents on...
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Power Quality Harmonics Analysis and Real Measurements Data Part 2 docx
Ngày tải lên :
19/06/2014, 08:20
... constant during the data window size used in the estimation process In real time, due to the switching on-off of power electronic equipments (devices) used in electric derives and power system...
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Power Quality Harmonics Analysis and Real Measurements Data Part 3 ppt
Ngày tải lên :
19/06/2014, 08:20
... sub-harmonics (interharmonics); dynamic case As we said in the beginning of this chapter, the off-on switching of the power electronics equipment in power system control may produce damped transients of...
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Power Quality Harmonics Analysis and Real Measurements Data Part 4 docx
Ngày tải lên :
19/06/2014, 08:20
... V.M.M Saiz and J Barros Gaudalupe, “Application of Kalman Filtering for Continuous Real-Time Traching of Power System Harmonics,” IEE Proc.-Gener Transm Distrib Vol 14, No 1, pp 13-20, 1998 S.A ... Absolute Value Based on Dynamic Filtering for on-line Power System Frequency Relaying”, Elect Machines & Power Systems, Vol 20, pp 569-592, 1992 S A Soliman, G S Christensen, D H Kelly, and K ... System Magnitude and Frequency Using Linear Kalman Filter: a Variable Frequency Model”, Elect Machines & Power Systems, Vol 20, pp 593-611, 1992 S A Soliman and G S Christensen, “Estimating of...
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Power Quality Harmonics Analysis and Real Measurements Data Part 5 doc
Ngày tải lên :
19/06/2014, 08:20
... Rules-based Algorithm for Detecting Transient Overvoltages due to Capacitor Switching and Statistical Analysis of Capacitor Switching in Distribution Systems, Proceedings of the IEEE Transmission and ... confidence level will widen the confidence interval For example, a 90% confidence interval for the achieved resistance will result in a 0.0717 ± 0.0055 confidence interval In the other words, the ... calculated by using Zeq h V h I h (10) 3.1 Characterization of the capacitor switching transient Traditionally, transients are characterized by their magnitude and duration For...
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Power Quality Harmonics Analysis and Real Measurements Data Part 6 pptx
Ngày tải lên :
19/06/2014, 08:20
... winding Noticeable simplification of parasitic capacitances distribution in VT winding can also be achieved by changing winding arrangement and introducing windings’ shields Example of influence of ... identification problems the model complexity should be kept within a reasonable level to allow achieving high usefulness Fig Parasitic capacitances arrangement in shielded VT windings Fig Typical ... Winding inductances and parasitic capacitances vary slightly with frequency increase therefore matching approximations should be taken into account for simplification fr fr 2 Lm C p C s...
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Power Quality Harmonics Analysis and Real Measurements Data Part 7 pdf
Ngày tải lên :
19/06/2014, 08:20
... availability of a matching transformer, only its transformation ratio is taken into account Thus, a very precise description of the converter operation in a wide range of load changes is achieved However, ... ≤ UCm (49) If the condition (49) is not fulfilled, then switching a pair of controllable switches off does not lead to natural switching the other pair of controllable switches on at zero voltage ... commutation Thus, automatic switching the converter off is avoided – a function, integrated in the control drivers of power transistors Defining the transformation ratio of the matching transformer The...
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Power Quality Harmonics Analysis and Real Measurements Data Part 8 doc
Ngày tải lên :
19/06/2014, 08:20
... Proceedings of SATECH'86, pp.55-68, Boston, USA Bankov, N (2009) Influence of the Snubbers and Matching Transformer over the Work of a Transistor Resonant DC/DC Converter Elektrotehnika&Elektronika ... ISSN: 0885-8993 5 Thermal Analysis of Power Semiconductor Converters Adrian Plesca Gheorghe Asachi Technical University of Iasi Romania Introduction Power devices may fail catastrophically if ... have their strength for different grades of complexity of the power circuit It is important to achieve an efficient tradeoff between the necessary accuracy, required simulation speed and feasibility...
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Power Quality Harmonics Analysis and Real Measurements Data Part 9 pptx
Ngày tải lên :
19/06/2014, 08:20
... Improve Power Quality with High Power UPQC Qing Fu, Guilong Ma and Shuhua Chen Sun Yat-sen University China Introduction An ideal AC power transmission is pure sinusoidal, both its voltage and its current ... increases possibility of damage to some critical loads such as storage devices and some micromachining devices Shunt APF can little with the damage caused by harmonic voltage in transmission ... Fig.20 shows the utility voltage waveform and Fig.21 shows its spectrums The harmonics during switching on the whole UPQC are shown in Tab.5 We can see that power quality is improved step by step...
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Power Quality Harmonics Analysis and Real Measurements Data Part 10 docx
Ngày tải lên :
19/06/2014, 08:20
... also used with industrial high-power single-phase loads and electrothermal appliances (Chicco et al., 2009; Chindris et al., 2002; Mayer & Kropik, 2005) This delta-connected set, more commonly ... also used in industrial high-power single-phase loads and electrothermal appliances (Chicco et al., 2009; Chindris et al., 2002; Mayer & Kropik, 2005) (a) (b) A Utility supply system A Utility ... electronics in the last few years and the use of step variable capacitor banks, (Barnes & Wong, 1991; Chindris et al., 2002) Steinmetz circuit design must consider circuit performance and behavior under...
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Power Quality Harmonics Analysis and Real Measurements Data Part 11 pptx
Ngày tải lên :
19/06/2014, 08:20
... of the International Conference on Energy Managment and Power Delivery, pp 657-661, 1995 Chicco, G., Chindris, M., Cziker, A., Postolache, P & Toader, C (2009) Analysis of the Steinmetz compensation ... equipments are classified into three different categories (Gowan, 2006): 4.3.1 Electric machines Electric machines which are inductive devices and as confirmed by simulation using them together with ... component-based indicators Proceedings of the IEEE Bucharest Power Tech Conference 2009, pp 1-6, 2009 Chindris, M., Cziker, A., Stefanescu, A S & Sainz, L (2002) Fuzzy logic controller for Steinmetz...
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Power Quality Harmonics Analysis and Real Measurements Data Part 12 docx
Ngày tải lên :
19/06/2014, 08:20
... these converters The power supplies employed in most personal computers are of the switching mode type In switching mode power supply, the 60 Hz AC voltage is converted to into DC through a single ... converter [13, 14] The main advantage of the switching mode power supply over the traditional linear power supply is its high energy efficiency since the switching elements used (BJT’s, MOSFETS) are ... general limits for various electrical equipments: a Synchronous machine: permissible stator current distortion < 1.4% b Asynchronous machines: permissible stator current distortion; 1.5% to 3.5% c...
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Power Quality Harmonics Analysis and Real Measurements Data Part 13 potx
Ngày tải lên :
19/06/2014, 08:20
... balancing of the three-phase network is currently achieved by a Steinmetz circuit, and the power factor correction is achieved by means of some step-switching capacitor banks (fig.1) In the electric...
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Power Quality Harmonics Analysis and Real Measurements Data Part 14 docx
Ngày tải lên :
19/06/2014, 08:20
... where converters with voltage notching, high pulse numbers, or PWM controls result in induced noise interference, current distortion, and local GPR at PV arrays (Chicco et al., 2009) A suitable ... S (2000) Power System Quality Assessment, John Wiley and Sons, ISBN 978-0-471-98865-6, New York Ching-Tzong Su, Chen-Yi Lin, & Ji-Jen Wong (2008) Optimal Size and Location of Capacitors Placed ... to capacitive coupling between the installation and earth, potential differences imposed by switching actions of the converter inject a capacitive ground current which can cause significant electromagnetic...
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Power Quality Monitoring Analysis and Enhancement Part 1 potx
Ngày tải lên :
19/06/2014, 11:20
... storage(SMES) Using the proposed switching strategy, the voltage of the inverter capacitors in SMES can be independently controlled and minimum power and switching losses can be achieved using this same strategy ... seven classes of signals, namely Sinusoidal Waveform, Capacitor Switching Transient, Flicker, Harmonics, Interruption, Notching and Sag, which is composed of four main stages: (1) signal analysis ... of reactive power demand from network is discussed Chapter 12 presents a novel and optimized switching strategy and control approach for a three level two-quadrant chopper in a three-level neutral...
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Power Quality Monitoring Analysis and Enhancement Part 2 potx
Ngày tải lên :
19/06/2014, 11:20
... seven classes of signals, namely Sinusoidal Waveform, Capacitor Switching Transient, Flicker, Harmonics, Interruption, Notching and Sag, which is composed by four main stages: (1) signal analysis ... types of PQ disturbances as follows: Pure sine (C1); Capacitor switching (C2); Flicker (C3); Harmonics (C4); Interruption (C5); Notching (C6); Sag (C7) The databases used for training and evaluation ... application, as in (Zhu et al., 2004; Chen & Zhu, 2007), the Daubechie “db4” wavelet was adopted to perform the DWT As can be seen in (Daubechies, 1992), the “db4” is a wavelet of support four, i.e.,...
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