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The Power Factor Correction of electrical loads is a problem common to
all industrial companies. Every user which utilizes electrical power
to obtain work in various forms continuously asks the mains to supply
a certain quantity of active power together with reactive power. Most
loads on an electrical distribution system can be placed in one of
three categories.
- Resistive
- Inductive
- Capacitive
The most common of these on modern systems is the inductive load.
Typical examples includes transformer, fluorescent lighting, AC
induction motors, Arc/induction, furnaces etc. which draw not, only
active power from the supply, but also inductive reactive power (KVAr).
Common characteristics of these inductive loads is that they utilize a
winding to produce an electromagnetic field which allows the motor or
transformer to function and requires certain amount of electrical
power in order to maintaining the field. Therefore Active Power (KW)
actually performs the work whereas Reactive Power (KVAr) sustain the
electro-magnetic field. This reactive power though is necessary for
the equipment to operate correctly but could be interpreted as an
undesirable burden on the supply.
Power Factor (Cosφ )
The power factor Cosφ of a load is defined as the ratio of active
power to apparent power i.e.

Apparent power is combination of reactive & active power. The closer
cosφ is to unity, the less reactive power is drawn from the
supply.
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Install a Power Factor
Correction System?
There are many objectives to be pursued in the planning of an
electrical system. In addition to safety and reliability, it is very
important to ensure that electricity is properly used. Each circuit,
each piece of equipment, must be designed so as to guarantee the
maximum global efficiency in transforming the source of energy into
work.
Among the measures that enable electricity use to be optimized,
improving the power factor of electrical systems is undoubtedly one of
the most important.
If we quantify this aspect from the utility company’s point of view,
raising the average operating power factor of the network from 0.7 to
0.9 means:
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These figures speak for themselves: it means saving hundreds of
thousands of tons of fuel and making several power plants and hundreds
of transformer rooms available.
Thus in the case of low power factors utility companies charge higher
rates in order to cover the additional costs they must incur due to
the inefficiency of the system that taps energy.
It is a well-known fact that electricity users relying on alternating
current – with the exception of heating elements – absorb from the
network not only the active energy they convert into mechanical work,
light, heat, etc. but also an inductive reactive energy whose main
function is to activate the magnetic fields necessary for the
functioning of electric machines.
The power factor is thus the ratio between active power and apparent
power (vectorial sum of active and reactive power), an indicator of
the quality of a facility’s electric system since the lower the power
factor is, the higher the inductive reactive component will be in
relation to the active component.
It is possible to produce reactive energy, where necessary, by
installing power capacitors or automatic power factor correction
systems. Capacitors absorb a current that is 180% out of phase with
the inductive reactive current; the two currents are algebraically
summed together so that circulating upstream from the point of
installation of the capacitor is a reactive current that is equal to
the difference between the inductive and capacitive currents.
The exchange occurs between the capacitor and user; this is why we say
that the capacitor supplies reactive energy to the user.
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Power flows with and without power factor
correction
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Theoretically speaking, when you must choose where to locate the
capacitive power the most appropriate solution from a technical
standpoint would be to assign each load its own power factor
correction capacitor, to be switched on together with the machine.
In practice, however, this entails excessive costs and technical
problems in most cases, since it requires the installation of a larger
number of low-power capacitors distributed in many different points,
which cannot be effectively monitored over time; plus little benefit
is to be derived from reducing losses in the cables, negligible
compared to those in the power transformer. Therefore, this solution
is only feasible in large facilities or where there are very high
power loads.
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The most appropriate power factor correction system thus consists in
the installation of an automatic capacitor bank on the bus bars of the
distribution panel and, if necessary, fixed capacitor banks for
correcting the power factor of the transformer, asynchronous motors
and any loads absorbing considerable quantities of reactive power.
The automatic system of the capacitor bank has the task of switching
in the necessary capacitance according to the load requirements at
each given moment.
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Choice & Calculation of The
Power Factor Correction?
Calculating the dimensions of the capacitor bank you need to install
in your system is very simple: note the cos of the system without
power factor correction and the cos you want to obtain and it will
take just a few calculations to derive the reactive power necessary in
order to reach the desired power factor. The power factor can differ
greatly between two users because it depends both on the type of
equipment installed and how it is used.
For example, asynchronous motors – by far the most widely used, though
brushless motors actuated by static AC/DC or AC/AC converters have
been gaining popularity in recent years – have a power factor that
varies greatly according to the motor load and type of construction
and can reach very low values in the absence of loads. Similar
observations may be made with respect to transformers. For all these
types of electric machines, recourse is often made to a fixed power
factor correction at the motor or transformer level. Other significant
differences can be seen in electrical equipment such as lamps,
furnaces, welding machines and converters.
Calculating of reactive power necessary power factor correction
P = active power of the system
cosφ0 = cosφ of system without power
factor correction
cosφ1 = cosφ you want to bring the
system to
Qc = reactive power of power factor
correction system to be installed
k =
cosφ0 and
cosφ1, this data is derived from the table
(next page)
Qc = P(tanφ0 - tanφ1)
=P.K
Correcting the Power Factor of MV / LV Transformers
It is always a good idea to ensure a power factor correction for MV /
LV transformers, since even when they are operating loadless (e.g.
during the night) they absorb reactive power, which must be
compensated. The exact capacitor power necessary may be calculated
using the formula below:
Q = Io% * Pn / 100
Io = loadless current (specified by the transformer manufacturer)
Pn = rated power of the transformer
Where alternatively, if the required data is not available, you can
refer to the table below, which differentiates among types of
transformers with NORMAL losses.
Reactive power for CORRECTING the POWER FACTOR CORRECTION NO LOAD of
50hz three phase transformation MV/LV(kvar)

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Real Time Power Factor
Correction (Activcomp) and What are Its Advantages ?
General information
Modern manufacturing plants are characterized by the use of highly
dynamic machinery, like welding loads. Alongside the undisputed
advantages of today’s modern techniques there is however the
disadvantage that the mains supply networks are often affected by
frequent load fluctuations and harmonic oscillation. It often leads to
unstable stress ratios. Flickering, excessive current and increased
losses in energy distribution. This reduces not only the supply
capacity but also impairs the function of sensitive electronics
controls.
Conventional reactive power compensation systems are designed for
optimizing the power factor and reducing the level of harmonic
oscillation, but offer no satisfactory solution for frequent load
fluctuations. The range of application of these units is the
compensation of static as well as fluctuating loads with switching
cycles measured by minutes.
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ACTIVCOMP
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- At each moment optimized
cosφ
- Soft switching without transients
- Flicker eliminated
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Application
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The real-time power factor compensation equipment of series
Activcomp
offers a solution. In these assemblies the classic components
controller and air contactor are substituted by a combination of
corresponding high speed controller and thyristor power modules type
Activcomp . This
system reacts immediately on load fluctuation and reactive power
surges will be neutralised in the supply network. The power factor is
optimised at each moment, on cycle to cycle basis, typical response
time less than 20 ms. The negative effects described above are reduced
to a minimum. This gives the consumer not only the advantage of a
stable supply ratio, but the ability to minimise energy distribution
and reduce costs. To increase the switching performance to an optimum,
the control signal for the steering of the capacitor banks can
alternatively be given directly by the logic control of bigger loads.
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Coefficient k by which to multiply the active energy consumed in KW
in order to determine the KVAR necessary for correcting the power
factor (Cosφ1 is the initial PF obtainable with
correction),
Recommender final
Cosφ = 0.95 upto1.00
|
| Coefficient
K |
| Value |
Cosφ |
|
Tgφ |
Cosφ |
0.85 |
0,86 |
0,87 |
0,88 |
0,89 |
0,90 |
0,91 |
0,92 |
0,93 |
0,94 |
0,95 |
0,96 |
0,97 |
0,98 |
0,99 |
1,00 |
| 3,18 |
0,30 |
2,560 |
2,586 |
2,613 |
2,640 |
2,667 |
2,695 |
2,754 |
2,754 |
2,785 |
2,817 |
2,851 |
2,888 |
2,929 |
2,977 |
3,037 |
3,180 |
| 3,0 |
0,31 |
2,447 |
2,474 |
2,500 |
2,527 |
2,555 |
2,583 |
2,611 |
2,641 |
2,672 |
2,704 |
2,738 |
2,775 |
2,816 |
2,864 |
2,924 |
3,067 |
| 2,96 |
0,32 |
2,341 |
2,367 |
2,394 |
2,421 |
2,448 |
2,476 |
2,505 |
2,535 |
2,565 |
2,598 |
2,632 |
2,669 |
2,710 |
2,758 |
2,818 |
2,961 |
| 2,86 |
0,33 |
2,241 |
2,267 |
2,294 |
2,321 |
2,348 |
2,376 |
2,405 |
2,435 |
2,465 |
2,498 |
2,532 |
2,569 |
2,610 |
2,657 |
2,718 |
2,861 |
| 2,77 |
0,34 |
2,146 |
2,173 |
2,199 |
2,226 |
2,254 |
2,282 |
2,310 |
2,340 |
2,371 |
2,403 |
2,437 |
2,474 |
2,515 |
2,563 |
2,623 |
2,766 |
| 2,68 |
0,35 |
2,057 |
2,083 |
2,110 |
2,137 |
2,164 |
2,192 |
2,221 |
2,250 |
2,281 |
2,313 |
2,348 |
2,385 |
2,426 |
2,473 |
2,534 |
2,676 |
| 2,59 |
0,36 |
1,972 |
1,998 |
2,025 |
2,052 |
2,079 |
2,107 |
2,136 |
2,166 |
2,196 |
2,229 |
2,263 |
2,300 |
2,341 |
2,388 |
2,449 |
2,592 |
| 2,51 |
0,37 |
1,891 |
1,918 |
1,994 |
1,971 |
1,999 |
2,027 |
2,055 |
2,085 |
2,116 |
2,148 |
2,187 |
2,219 |
2,260 |
2,308 |
2,368 |
2,511 |
| 2,43 |
0,38 |
1,814 |
1,841 |
1,867 |
1,894 |
1,922 |
1,950 |
1,979 |
2,008 |
2,039 |
2,071 |
2,105 |
2,143 |
2,184 |
2,231 |
2,292 |
2,434 |
| 2,36 |
0,39 |
1,741 |
1,768 |
1,794 |
1,821 |
1,849 |
1,877 |
1,905 |
1,935 |
1,966 |
1,998 |
2,032 |
2,069 |
2,110 |
2,158 |
2,219 |
2,361 |
| 2,29 |
0,40 |
1,672 |
1,698 |
1,725 |
1,752 |
1,779 |
1,807 |
1,836 |
1,865 |
1,896 |
1,928 |
1,963 |
2,000 |
2,041 |
2,088 |
2,149 |
2,291 |
| 2,22 |
0,41 |
1,605 |
1,631 |
1,658 |
1,685 |
1,712 |
1,740 |
1,796 |
1,799 |
1,829 |
1,862 |
1,896 |
1,933 |
1,974 |
2,022 |
2,082 |
2,225 |
| 2,16 |
0,42 |
1,514 |
1,567 |
1,594 |
1,621 |
1,648 |
1,676 |
1,705 |
1,735 |
1,766 |
1,798 |
1,832 |
1,869 |
1,910 |
1,958 |
2,018 |
2,161 |
| 2,10 |
0,43 |
1,480 |
1,506 |
1,533 |
1,560 |
1,587 |
1,615 |
1,644 |
1,674 |
1,704 |
1,737 |
1,771 |
1,808 |
1,849 |
1,897 |
1,957 |
2,100 |
| 2,04 |
0,44 |
1,421 |
1,448 |
1,474 |
1,501 |
1,526 |
1,557 |
1,585 |
1,615 |
1,646 |
1,678 |
1,712 |
1,749 |
1,790 |
1,838 |
1,898 |
2,041 |
| 1,98 |
0,45 |
1,365 |
1,391 |
1,418 |
1,445 |
1,472 |
1,500 |
1,529 |
1,559 |
1,589 |
1,622 |
1,656 |
2,693 |
1,734 |
1,781 |
1,842 |
1,985 |
| 1,93 |
0,46 |
1,311 |
1,337 |
1,364 |
1,391 |
1,418 |
1,446 |
1,475 |
1,504 |
1,535 |
1,567 |
1,602 |
1,639 |
1,680 |
1,727 |
1,788 |
1,930 |
| 1,88 |
0,47 |
1,258 |
1,285 |
1,311 |
1,338 |
1,366 |
1,394 |
1,422 |
1,452 |
1,483 |
1,515 |
1,549 |
1,.586 |
1,627 |
1,675 |
1,736 |
1,878 |
| 1,83 |
0,48 |
1,208 |
1,234 |
1,261 |
1,288 |
1,315 |
1,343 |
1,372 |
1,402 |
1,432 |
1,456 |
1,499 |
1,536 |
1,577 |
1,625 |
1,685 |
1,828 |
| 1,78 |
0,49 |
1,159 |
1,189 |
1,212 |
1,239 |
1,267 |
1,295 |
1,323 |
1,353 |
1,384 |
1,416 |
1,450 |
1,487 |
1,528 |
1,576 |
1,637 |
1,779 |
| 1,73 |
0,50 |
1,112 |
1,139 |
1,165 |
1,192 |
1,220 |
1,248 |
1,276 |
1,306 |
1,337 |
1,369 |
1,403 |
1,440 |
1,481 |
1,529 |
1,590 |
1,732 |
| 1,69 |
0,51 |
1,067 |
1,093 |
1,120 |
1,147 |
1,174 |
1,202 |
1,231 |
1,261 |
1,391 |
1,324 |
1,358 |
1,395 |
1,436 |
1,484 |
1,544 |
1,687 |
| 1,64 |
0,52 |
1,023 |
1,049 |
1,079 |
1,103 |
1,130 |
1,158 |
1,187 |
1,217 |
1,247 |
1,280 |
1,314 |
1,351 |
1,392 |
1,440 |
1,500 |
1,643 |
| 1,60 |
0,53 |
0,980 |
1,007 |
1,033 |
1,060 |
1,088 |
1,116 |
1,144 |
1,174 |
1,205 |
1,237 |
1,271 |
1,308 |
1,349 |
1,397 |
1,458 |
1,600 |
| 1,56 |
0,54 |
0,939 |
0,965 |
0,992 |
1,019 |
1,046 |
1,074 |
1,103 |
1,133 |
1,163 |
1,196 |
1,230 |
1,267 |
1,308 |
1,356 |
1,416 |
1,556 |
| 1,52 |
0,55 |
0,899 |
0,925 |
0,952 |
0,979 |
1,006 |
1,034 |
1,063 |
1,092 |
1,123 |
1,156 |
1,190 |
1,227 |
1,268 |
1,315 |
1,376 |
1,518 |
| 1,48 |
0,56 |
0,860 |
0,886 |
0,913 |
0,940 |
0,967 |
0,995 |
1,024 |
1,053 |
1,084 |
1,116 |
1,151 |
1,188 |
1,229 |
1,276 |
1,337 |
1,476 |
| 1,44 |
0,57 |
0,822 |
0,848 |
0,875 |
0,902 |
0,926 |
0,957 |
0,986 |
1,015 |
1,046 |
1,079 |
1,113 |
1,150 |
1,191 |
1,.238 |
1,299 |
1,441 |
| 1,40 |
0,58 |
0,785 |
0,811 |
0,838 |
0,865 |
0,892 |
0,920 |
0,949 |
0,979 |
1,009 |
1,042 |
1,076 |
1,113 |
1,154 |
1,201 |
1,262 |
1,405 |
| 1,37 |
0,59 |
0,749 |
0,775 |
0,802 |
0,829 |
0,56 |
0,884 |
0,913 |
0,942 |
0,973 |
1,006 |
1,040 |
1,077 |
1,118 |
1,165 |
1,226 |
1,368 |
| 1,33 |
0,60 |
0,714 |
0,740 |
0,767 |
0,794 |
0,821 |
0,849 |
0,878 |
0,907 |
0,938 |
0,970 |
1,005 |
1,042 |
1,083 |
1,130 |
1,191 |
1,333 |
| 1,30 |
0,61 |
0,679 |
0,706 |
0,732 |
0,759 |
0,787 |
0,815 |
0,843 |
0,873 |
0,904 |
0,936 |
0,970 |
1,007 |
1,048 |
1,096 |
1,157 |
1,299 |
| 1,27 |
0,62 |
0,646 |
0,672 |
0,699 |
0,726 |
0,753 |
0,781 |
0,810 |
0,839 |
0,870 |
0,903 |
0,937 |
0,374 |
1,015 |
1,062 |
1,123 |
1,265 |
| 1,23 |
0,63 |
0,613 |
0,639 |
0,666 |
0,693 |
0,720 |
0,748 |
0,777 |
0,807 |
0,837 |
0,870 |
0,904 |
0,941 |
0,982 |
1,030 |
1,090 |
1,233 |
| 1,20 |
0,64 |
0,581 |
0,607 |
0,634 |
0,661 |
0,688 |
0,.716 |
0,745 |
0,775 |
0,805 |
0,838 |
0,872 |
0,909 |
0,950 |
0,998 |
1,058 |
1,201 |
| 1,17 |
0,65 |
0,549 |
0,579 |
0,602 |
0,629 |
0,657 |
0,685 |
0,714 |
0,743 |
0,774 |
0,806 |
0,840 |
0,877 |
0,919 |
0,966 |
1,027 |
1,169 |
| 1,14 |
0,66 |
0,519 |
0,545 |
0,572 |
0,599 |
0,626 |
0,654 |
0,683 |
0,712 |
0,743 |
0,775 |
0,810 |
0,847 |
0,888 |
0,935 |
0,996 |
1,138 |
| 1,11 |
0,67 |
0,488 |
0,515 |
0,541 |
0,568 |
0,596 |
0,624 |
0,652 |
0,682 |
0,713 |
0,.745 |
0,779 |
0,816 |
0,857 |
0,905 |
0,966 |
1,108 |
| 1,08 |
0,68 |
0,459 |
0,485 |
0,512 |
0,539 |
0,566 |
0,594 |
0,623 |
0,652 |
0,683 |
0,715 |
0,750 |
0,787 |
0,828 |
0,875 |
0,936 |
1,078 |
| 1,05 |
0,69 |
0,429 |
0,456 |
0,482 |
0,509 |
0,537 |
0,565 |
0,593 |
0,623 |
0,654 |
0,686 |
0,702 |
0,57 |
0,798 |
0,846 |
0,907 |
1,049 |
| 1,02 |
0,70 |
0,400 |
0,427 |
0,453 |
0,480 |
0,508 |
0,539 |
0,565 |
0,594 |
0,625 |
0,.657 |
0,692 |
0,729 |
0,770 |
0,817 |
0,878 |
1,020 |
| 0,99 |
0,71 |
0,372 |
0,398 |
0,425 |
0,452 |
0,480 |
0,508 |
0,536 |
0,566 |
0,597 |
0,629 |
0,663 |
0,700 |
0,714 |
0,789 |
0,849 |
0,992 |
| 0,96 |
0,72 |
0,344 |
0,370 |
0,397 |
0,424 |
0,452 |
0,480 |
0,508 |
0,538 |
0,569 |
0,601 |
0,635 |
0,672 |
0,713 |
0,761 |
0,821 |
0,964 |
| 0,94 |
0,73 |
0,316 |
0,343 |
0,370 |
0,396 |
0,424 |
0,452 |
0,481 |
0,510 |
0,541 |
0,.573 |
0,608 |
0,645 |
0,686 |
0,733 |
0,794 |
0,936 |
| 0,91 |
0,74 |
0,289 |
0,316 |
0,342 |
0,369 |
0,397 |
0,425 |
0,453 |
0,483 |
0,514 |
0,546 |
0,580 |
0,617 |
0,658 |
0,706 |
0,766 |
0,909 |
| 0,88 |
0,75 |
0,262 |
0,289 |
0,315 |
0,342 |
0,370 |
0,398 |
0.,426 |
0,456 |
0,487 |
0.,519 |
0,553 |
0,590 |
0,631 |
0,679 |
0,739 |
0,882 |
| 0,86 |
0,76 |
0,235 |
0,262 |
0,288 |
0,315 |
0,343 |
0,371 |
0,400 |
0,429 |
0,460 |
0,492 |
0,526 |
0,563 |
0,605 |
0,652 |
0,713 |
0,855 |
| 0,83 |
0,77 |
0,209 |
0,235 |
0,262 |
0,289 |
0,316 |
0,344 |
0,373 |
0,403 |
0,433 |
0,466 |
0,500 |
0,537 |
0,578 |
0,626 |
0,686 |
0,829 |
| 0,80 |
0,78 |
0,183 |
0,209 |
0,236 |
0,263 |
0,290 |
0,318 |
0,347 |
0,376 |
0,407 |
0,439 |
0,474 |
0,511 |
0,552 |
0,599 |
0,660 |
0,.802 |
| 0,78 |
0,79 |
0,156 |
0,183 |
0,209 |
0,236 |
0,264 |
0,292 |
0,320 |
0,350 |
0,381 |
0,413 |
0,447 |
0,484 |
0,525 |
0,573 |
0,634 |
0,776 |
| 0,75 |
0,80 |
0,130 |
0,157 |
0,183 |
0,210 |
0,238 |
0,266 |
0,294 |
0,324 |
0,355 |
0,387 |
0,421 |
0,458 |
0,499 |
0,547 |
0,608 |
0,750 |
| 0,72 |
0,81 |
0,104 |
0,131 |
0,157 |
0,184 |
0,212 |
0,240 |
0,268 |
0,298 |
0,329 |
0,361 |
0,395 |
0,432 |
0,473 |
0,521 |
0,581 |
0,724 |
| 0,70 |
0,82 |
0,078 |
0,105 |
0,131 |
0,158 |
0,186 |
0,214 |
0,242 |
0,272 |
0,303 |
0,335 |
0,369 |
0,406 |
0,447 |
0,495 |
0,556 |
0,698 |
| 0,67 |
0,83 |
0,052 |
0,079 |
0,105 |
0,132 |
0,160 |
0,188 |
0,216 |
0,246 |
0,277 |
0,309 |
0,343 |
0,380 |
0,421 |
0,469 |
0,530 |
0,672 |
| 0,65 |
0,84 |
0,029 |
0,053 |
0,079 |
0,106 |
0,134 |
0,162 |
0,190 |
0,220 |
0,251 |
0,283 |
0,317 |
0,354 |
0,395 |
0,443 |
0,503 |
0,646 |
| 0,62 |
0,85 |
|
0,026 |
0,053 |
0,080 |
0,107 |
0,135 |
0,164 |
0,194 |
0,225 |
0,257 |
0,291 |
0,328 |
0,369 |
0,417 |
0,477 |
0,620 |
| 0,59 |
0,86 |
|
|
0,027 |
0,054 |
0,081 |
0,109 |
0,138 |
0,167 |
0,198 |
0,230 |
0,265 |
0,302 |
0,343 |
0,390 |
0,451 |
0,593 |
| 0,57 |
0,87 |
|
|
|
0,027 |
0,054 |
0,082 |
0,111 |
0,141 |
0,172 |
0,204 |
0,238 |
0,275 |
0,316 |
0,364 |
0,424 |
0,567 |
| 0,54 |
0,88 |
|
|
|
|
0,027 |
0,055 |
0,084 |
0,114 |
0,145 |
0,177 |
0,211 |
0,248 |
0,289 |
0,337 |
0,397 |
0,540 |
| 0,51 |
0,89 |
|
|
|
|
|
0,028 |
0,057 |
0,086 |
0,117 |
0,149 |
0,184 |
0,221 |
0,262 |
0,309 |
0,370 |
0,512 |
| 0,48 |
0,90 |
|
|
|
|
|
|
0,029 |
0,058 |
0,089 |
0,121 |
0,156 |
0,193 |
0,234 |
0,281 |
0,342 |
0,484 |
| 0,46 |
0,91 |
|
|
|
|
|
|
|
0,030 |
0,060 |
0,093 |
0,127 |
0,.164 |
0,205 |
0,253 |
0,313 |
0,456 |
| 0,43 |
0,92 |
|
|
|
|
|
|
|
|
0,031 |
0,063 |
0,097 |
0,134 |
0,175 |
0,223 |
0,284 |
0,426 |
| 0,46 |
0,93 |
|
|
|
|
|
|
|
|
|
0,032 |
0,067 |
0,104 |
0,145 |
0,192 |
0,253 |
0,395 |
| 0,36 |
0,94 |
|
|
|
|
|
|
|
|
|
|
0,034 |
0,071 |
0,.112 |
0,160 |
0,220 |
0,363 |
| 0,33 |
0,95 |
|
|
|
|
|
|
|
|
|
|
|
0,037 |
0,078 |
0,126 |
0,186 |
0,329 |
| 0,29 |
0,96 |
|
|
|
|
|
|
|
|
|
|
|
|
0,041s |
0,089 |
0,149 |
0,292 |
| 0,25 |
0,97 |
|
|
|
|
|
|
|
|
|
|
|
|
|
0,048 |
0,108 |
0,251 |
| 0,20 |
0,98 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
0,061 |
0,203 |
| 0,14 |
0,99 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
0.142 |
|
|
Advantages of Thyristor Switched Over Electro-Mechanical
Compensation System ?
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Fast and Accurate Compensation
The Activcomp is a Transient Free Fast Compensation System. It is used
for Power Factor Correction & Harmonic Filter. The compensation is
based on averaging the FFT analysis of each cycle, resulting in more
accurate compensation, even in the presence of harmonics.
Simultaneous Group Connection
When load changes require connection or disconnection of more than one
step, the Activcomp controls the switching of as many steps as
required at precisely the same time. Simultaneous connection or
disconnection provides the following benefits :
• Fast full compensation.
• For Eg., with 1:2:2 system configuration and groups 1 & 2 are
connected. When 1 more step is required, group 3 will
be connected
simultaneously while group 1 is disconnected.
• Real binary sizing - 1:2:2 is exactly the same as 1:1:1:1:1.
Transient-free Switching
Electronic switching technology prevents any transients typically
associated with conventional capacitor switching. This is extremely
important in sites with sensitive electronic equipment, such as
hospitals, data centers and facilities.
Fixed Capacity & Filter Characteristics
The capacity of the Activcomp capacitors is virtually permanent over
the years, which prevents the need to replace capacitors. Moreover the
tuning frequency remains constant over time, which allows system
performance to remain at the highest possible level.
There is an ongoing cumulative reduction of capacity in electro
mechanically switched PFC systems due to the effect of transients
during connections and disconnection. This can be detrimental to
detuned electro mechanically switched systems where the changes in
ratio between the capacitors/reactors shift the resonance frequency,
which may result in resonance. The Activcomp prevents these
conditions.
Long Life and Reduced Maintenance Costs
Neptune Activcomp reduces site maintenance costs by increasing the
lifetime of:
• Switching elements
• Capacitors
• Sensitive electronic equipment
Capacitor Duty Cycle-SCAN Mode
The unique SCAN feature protects the Activcomp’s capacitors &
reactors, increases their life span. Simultaneous connection and
disconnection of steps in FIFO (First In First Out) manner is shown in
diagram on the previous page.
The scan feature reduces the average current in the capacitors and the
reactors and therefore providing the following advantages:
• Reduces substantially the increase of temperature in these elements
resulting in longer life expectancy of the
inductors and capacitors.
• Reduces the effect of over-current and over voltage caused by the
harmonics on the capacitors and inductors.
• The tuning frequency of the de-tuned filter or tuned filter is
stable due to the fact that the capacitor value (micro farad)
doesn't
change due to the low temperature achieved by the scan mode.
Easy to Use and Maintain
The advanced DSP and microprocessor-based controller, with its large
full graphic LCD display, provides easy-to-use operation. The
controller includes a complete electrical measurement system, which
can replace a facilities main monitoring meter. The controller
operates the BIT (Built In Test), which reports system or network
conditions. The optional PowerlQ software can remotely control all
Activcomp operation and display additional system power information.
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Power Factor Corrections Capacitors.
Unlike most electrical equipment, power factor correction capacitors,
each time they are energized, continuously operate at full load or at
loads which differ from this value only as a consequence of variations
in voltage and frequency.
Overstressing and overheating shorten the life span of the capacitor.
For this reason the operating conditions (temperature, voltage and
current) must be carefully controlled in order to obtain optimum
results as respects the lifespan of the capacitor.
Voltage
The capacitors are produced in accordance with reference standards EN
60831-1/2 which regulate their manufacturing, testing, installation
and application and which indicate the following maximum values for
over voltage applicable to the capacitors:
+10% for 8 hours every 24 hours
+15% for 30 minutes every 24 hours |
+20% for 5 minutes every 24 hours
+30% for 1 minute every 24 hours. |
Over voltages in excess of 15% should not occur more than 200 times in
the lifespan of the capacitor. Often when there is the presence of
overload conditions during service, in the presence of a moderate
harmonic load for example, it is common to use oversized capacitors in
terms of voltage.
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In such cases the output power at operating voltage will be reduced
with respect to that of the rated load. It is advisable to evaluate
the reduction experienced in the output power on the basis of the
correlation between the operating voltage and the rated voltage.
The following table indicates the output power of a 100 kvar capacitor
used on a 400 V network with a rated voltage of 450 V, 500 V and 550 V.
|
| Un |
450 |
500 |
550 |
| Q output kvar
|
79 |
64 |
53 |
|
|
Temperature
The temperature of the capacitor during operation is the parameter
that, along with the voltage, has the greatest influence on the life
span of the capacitor. It is important that the capacitor always be
placed in a position where the cooling air can freely circulate,
avoiding the radiant heat of hot surfaces of other components. When
the capacitors are placed in closed cabinets it is necessary to have
air vents which allow for an easy exchange of air between the interior
and exterior of the cabinet. On the other hand, when the degree of
protection of the cabinet does not permit this exchange of air, the
internal spaces must be much larger and the positioning of the
capacitors must be carefully studied to permit the necessary channels
which allow for the circulation of cooling air. In this case the
forced cooling air will have to be provided by suitable fans. As a
rule the temperature of the cooling air inside the cabinet should not
differ by more than 5ºC with respect to the external air at the
control panel.
Cooling air temperature
This is the temperature of cooling air measured at the hottest point
of the bank of capacitors, under working conditions, halfway between
two capacitors or on the surface of one of these.
Categories of ambient air temperature
This represents the range of cooling air temperatures in which the
capacitor is designed to operate. As a rule there are 4 categories
represented by a number and a letter or by two numbers as shown in the
table.
|
|
Categories |
Ambient air temperature |
| |
|
Max |
|
Highest mean
over any period of |
|
24h |
1year |
|
| -25/A |
-25+40°C. |
40 |
40 |
40 |
| -25/B |
-25+45°C |
45 |
35 |
35 |
| -25/c |
-25+50°C |
50 |
40 |
40 |
| -25/D |
-25+55°C |
55 |
45 |
35 |
|
|
The first number represents the minimum temperature of the cooling air
at which the capacitor can be energized (-25ºC) on request -40ºC. The
letter or the second number represents the upper limit of the
temperature range and precisely the max. value indicated in the table.
Residual voltage
This is the voltage that remains after disconnecting the capacitor
from the network. This voltage must be eliminated in order to avoid
dangerous conditions for the operator. All three-phase capacitors are
equipped with discharge devices, that reduce the residual voltage to a
value of minimum 75 V after 3 minutes.
It is important to bear in mind that the capacitors cannot be
energized if there is a residual voltage of more than 10% across them.
Particular attention must therefore be applied in harmonizing the
capacitor discharge times with the response times of the control
devices (Regulators). In cases where the lag time of the regulators
are shorter than the discharge time of the capacitor, it is necessary
to provide additional discharge devices until the connection occurs
with a residual voltage of less than 10%.
To reduce the residual voltage to 50 V in 20 seconds in batteries with
a power less than or equal to 20 kvar at a voltage of 400 V, use 3
metal oxide resistors of 68 kohm, 4W in a delta connection.
Max current
The capacitors are made to function conforming to standards EN 60831 -
1/2 continuously at an effective value at last of 1.3 times the value
of the current at rated voltage and frequency. Bearing in mind the
capacitance tolerance, the maximum current can arrive to 1.5 In, the
value to which it is necessary to refer in the scaling of the line of
control and protection devices. This overcurrent factor can be
determined by the
combined effect of harmonics, overvoltages and capacitance tolerance.
Max inrush current
Transient overcurrents having elevated amplitudes and high frequencies
occur when the capacitors are switched in to the circuit. This is
especially true when a bank of capacitors are put in a parallell
connection with other already-energized capacitors. It may therefore
be necessary to reduce these transient overcurrents to acceptable
values both for the capacitor and the contactor used by connecting the
capacitor using suitable devices (resistors or reactors) in the power
circuit of the battery. The peak value of the overcurrent caused
during maneuvering operations must be limited to a maximum value of
100 In (crest
value of the 1st cycle).
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