advantages and disadvantages of using delta or star connected capacitor banks for power factor improvement?
412964
use the delta when you are starting a large motor since it can be hooked to energize only part of the windings of the motor at a time this allows for less amperage to be used to get the thing turning
775380
You have to consider steady-state security and dynamic security. It is the ability to provide rated voltage at rated frequency, and have enough "margin of safety". For example, an overloaded generator is a weak link in the overall security of the system, because it would be the one most likely to fail. An overloaded Tx line would probably sag so much that it might be susceptible to line-to-line faults in a wind. One way of estimating security margins (steady-state) is to run power flows at the current state of the system, and using short-term load-projections, run more power flow computations, and estimate the operating margin you have before over-load relays or transformer protection start operating and cause cascade failures.
702129
I've found a good site introducing and explaining the voltage and phase relationships between delta and wye 3 phase transformers. Try www.elec-toolbox.com/usefulinfo/xfmr-3ph.htm\nI hope that this proves useful for your research.
572004
You mean VFD, Variable Frequency Drives. Also known as inverters. All the newer VFD's use a IGBT active power module device. The IGBT is mainly used in switching power supplies and motor control applications.\n\nAn example of use: Reliable IGBTs is a key enabler for electric vehicles and hybrid cars. Toyota's second generation hybrid Prius has a 50 kW IGBT inverter controlling two AC motor/generators connected to the DC battery pack.\n\nCheck out the following links:
198054
Consumers do not improve power factor. The power generator companies improve the power factor or else they're simply waiting energy if it too low. The best way to do this is to install large capacitors in select areas on the grid. This counteracts the inductance in the wires which is responsible for creating the bad power factor.
842836
The best answer you can get is by going to howstuffworks.com. They have a very detailed description.\n\nBut basically, capacitors store electric energy and release it when it is needed most. A capacitor has two metal plates inside it, to hold the charge, and a material called a dielectric, which could be just about anything that is non-conductive, to keep the plates from touching each other. (I think that's what you were asking about the material between the capacitor.)\nThe one plate connected to the positive power loses electrons to the power source, and the other is connected to the negative, and gains electrons, thereby becoming electrically charged.\nA capacitor can be used to smooth out a DC voltage, supply extra power to a motor on start-up, or a large number of other things.\nBy the way, capacitance is measured in Farads, or, more commonly, micro-farads, nano-farads and pico-farads, which are very small parts of a farad. 10 to the power of -6, -9, and -12, respectively.
840963
Power Factor Correction:\nIf an inductive load with an active power demand P has an uncorrected power factor of cosf1 lagging, and is required to have a corrected power factor of cosf2 lagging, the uncorrected and corrected reactive power demands, Q1 and Q2, are:\nQ1 = P tanf1\nQ2 = P tanf2\nwhere tanfn = (1 / cos2fn - 1)½ \n\nThe leading (capacitive) reactive power demand QC which must be connected across the load is:\nQC = Q1 - Q2 = P (tanf1 - tanf2)\n\n\nThe uncorrected and corrected apparent power demands, S1 and S2, are related by:\nS1cosf1 = P = S2cosf2\nComparing corrected and uncorrected load currents and apparent power demands:\nI2 / I1 = S2 / S1 = cosf1 / cosf2 \n\nIf the load is required to have a corrected power factor of unity, Q2 is zero and:\nQC = Q1 = P tanf1\nI2 / I1 = S2 / S1 = cosf1 = P / S1 \n\n\n\nModern capacitor values:\nIn around 1970, a standardized set of capacitor base numbers was devised so that the value of any modern electrolytic capacitor could be derived from multiplying one of the modern conventional base numbers 1.0, 2.2, 3.3, or 4.7, by a power of ten. Therefore, it is common to find capacitors with values of 10, 22, 33, 47, 100, 220, and so on. Using this method, values ranging from 0.1 to 4700 are common in most applications. Values are generally in microfarads (µF).\n\nHow standardized values help:\n\nMost electrolytic capacitors have a tolerance range of 20 %, meaning that the manufacturer guarantees that the actual value of the capacitor lies within 20 % of its labeled value.\n\nA 10 µF capacitor, for example, may in actuality be as low as 8 µF whereas a capacitor marked 8 µF may in fact be as high as 9.6 µF. This causes an overlap of 1.6 µF. The standardized base values help this by alleviating overlaps due to tolerance, illustrated by the following table:\n\nThe left numbers are the base values. \nThe center numbers are the differences based on ± 20 % tolerance. \nThe numbers on the right illustrate the range of actual values by applying the tolerance. \nIn an effort to cut costs in the manufacturing process, the number of possible values was limited, because having overlapping values would be viewed as unneeded and redundant, since for most practical applications, having a 20 % (or even higher) tolerance did not adversely affect the functionality of the device. The reduction of variations in the product allowed companies to produce greater quantities of existing samples. This in turn, allowed for lower cost components.\n\n(Retrieved from "http://en.wikipedia.org/wiki/Electrolytic_capacitor_value"\nhttp://en.wikipedia.org/wiki/Power_factor_correction_unit)\n\nWHY CAN CAPACITORS "CORRECT" power factor on circuits involving motors? We know that in inductive apparatus, such as an a-c motor, current lags voltage. Capacitors draw current that leads the voltage-therefore, they offset the lag. \n\nBut why does current lead voltage in a capacitor? Back when we were learning basic electricity, a common explanation went like this: When the circuit is first closed, current must flow into the capacitor to build up a charge on the plates before voltage can build up on those plates. Hence, current must lead voltage. \n\nThat explanation leaves much to be desired. More often, "fundamentals" training begins with lead-lag relationships as "givens," and only the consequences of those relationships are explained in detail. \n\nWhat, then, is the real reason we say that, in a "perfect" capacitor, the current not only leads the voltage in time phase, but leads by exactly 90 degrees? Why does current lead, and why not some other angle? \n\nFORE MORE PL. VISIT:\nhttp://www.bowest.com.au/library/electric.html
722546
I use a power inverter.
450183
this might prove to be useful:\nhttp://islab.oregonstate.edu/koc/ece575/02Project/Mor/
827050
Yupp... but unfortunately is a hardcopy on my desk. Perhaps you may straight to tell us what\n\n1. You are designing from HT to Transformer 11kV / 415V\n2. You are designinig from Transformer to LV ??\n3. What is the kVA of the transfomer?
324733
lol here you go... this question is asked all the time in wwiionlines/CSF \n\nfirst look at how much stuff this power supply will be feeding... \n\nhere is a rule of thumb \n\nno less then 500W for a gaming computer\n\nno less then 18A in each (if more then one) 12V+ rail. \n\nno less then 79% efficency\n\nalso take a look at the DB rating of the psu \n\ni have a Enermax 600W Sli noisetaker \n\n600W Peak \n38A 12V+ rail(s)\n96% Effiecncy \n31Db at normal operation
913471
In a purely resistive circuit, the power factor (PF) is 1 and you *can't* adjust it.\n\nAnd, since this is the 3'rd time you've asked the question and gotten the same answer from one other person and myself, do you even know what 'Power Factor' *is*?\n\n\nDoug
916046
See Resources below\n\n***WARNING: When working with power supplies, be sure to read up on power supply safety.  It is quite dangerous (possibly FATAL) to work on power supplies if you do NOT have knowledge about how to SAFELY work with power supplies***
61904
Is there any specific reason you want to change the power supply?  Not enough connectors?  Is it failing?  Power supply upgrades usually are only done when a unit fails or if you are adding more hardware into the system than the PS can handle... If neither is the case, you may end up spending alot of cash on a good aftermarket supply and it will do absolutely nothing to make your machine run better.  \n\nPower supplies simply convert AC voltage to the required DC supply lines needed for the machine.  They do not do anything to improve the performance.
1165747
Nothing is for free.  Peripherals you put inside your computer take certain amount of power.   Motherboard, keyboard, mouse, graphics card, hard drive, cd drive, and etc. etc. all require certain amount of power.\n\nThe issue with have a good power supply isn't about speed.  It's about stability.  Your power supply is in charge of converting the AC current from the wall to DC.  An ideal power supply will provide stable DC current with very little ripple current.   Ripple current is the deviating fluctuation that is present in all DC current provided by a power supply.\n\nAnd it is possible to have too much wattage but only in extreme cases.  Electronic device like power supplies work with tolerance levels usually given in percentages.  So two different rated power supplies built with 5% tolerance will have different tolerances.  With a lot of power you lose a precision.  With precision you use a certain amount of power.  (Analogy would be fidelity and power in audio terms.)
76334
In alternating current circuits, energy storage elements such as inductance and capacitance may result in periodic reversals of the direction of energy flow. The portion of power flow that, averaged over a complete cycle of the AC waveform, results in net transfer of energy in one direction is known as real power. That portion of power flow due to stored energy, that returns to the source in each cycle, is known as reactive power.
60886
(hm hm condenser...you must be old school)well we can and kind of have in ways. Helmholtz described charge starge devices that are largely used today as "batteries" for memeory backup. such a charge storage device has great capacity and unlike the capacitors it can be put in series to increase bothe input and output voltage. the internal dielectric is not very great so there is considerable leakage compared to a tradition electrolytic. the scheme used today comprises as a layer of activated charcoal a dielectric layer and then another charcoal layer. you can buy these easity in small units that are as muc as a few fards and a few voltas. \nwhen the lighting strikes, though, the power factor is so low that the internal wiring are likely to burn out. there is c acomapnay, (i dont remember the name), is designing such "batteries" as a methos for propelling vehicles. i think the name of the comapny is Maxwell (not be confused with Maxell).\ni personally have experimented in creating such batteries that store energy as dc but when released it is AC! such a battery would be used in vehicles with more efficient motors and safer too. An ac battery of course would require controls and would use similar schema as what Helmholz described.....\nthere is a great book on Helmholz publised by UC press that leaves one to think that this amn knew way more than einstein ever did and his genius out stripped einstein and leaves him in the dust.\nalso one does no need lightning. therer are enough free electrons in the air to creat a good chrage over time. take a CRT from stock never used is ok, and touch the anode dimple. knocks you right back. that is a charge from the air.