VMtec, Germany

VMtec Maschinen-und
Anlagenbau GmbH

Wiesbaden Park str 23
65189 Wiesbaden, Park str 23, Deutschland
Tel: 0611 9005701
Fax: 0611 9005702
E-Mail: info@vmtec.de


VMtec Maschinen-und Anlagenbau GmbH
Paderborn

Sommerbrede 11,
D-33104 Paderborn, Deutschland
Tel: +49-5252-9170078
Fax: +49-5252-9333075
Mobil: +49-17670518235
E-Mail: a.friesen@vmtec.de
Skype: andreas.friesen1966

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POWER FACTOR CORRECTION: TECHNICAL REASONS

Recent energy market deregulation, along with new potential energy supplier rising, had lead to many and different type of invoicing whichare not very clear in showing Power Factor up.

However as energy final price is steady growing, to correct power factor is becoming more and more convenient. In most of the cases power factor improvement device prime cost is paid back in few months.

Technical-economical advantages of the installation of a capacitor
bank are the following:

  • decrease of the losses in the network and on the transformers caused by the minor absorbed current
  • decrease of voltage on lines
  • optimisation of the system sizing

The current I, that flows in the system, is calculated by

where

P = Active Power,

V = Nominal Voltage.

While cosϕ increases, with the same absorbed power we can obtain a reduction in the value of the current and as a consequence the losses in the network and on the transformers are reduced. Therefore we have an important saving on the size of electrical equipment used on a system. The best system sizing has some consequence on the line voltage drop. We can easily see that looking at the following formula:

where
P= active power on the network (kW)
Q= reactive power on the network (kvar)
while R is the wire resistance and X its reactance (R<<X). The capacitor bank installation reduces Q so we have a lower voltage drop. If, for a wrong calculation of the installed capacitor bank value, the reactive part of the above equation becomes negative, instead of a reduction of the voltage drop we have an increasing of the voltage at the end of the line (Ferranti Effect) with dangerous consequence for the installed loads.

Hereinafter some examples:

1) Copper wire 3x25mm2, length 100m, 40kW load at 400Vac

2) 100kVA transformer

As we can see as the power factor increases we have fewer losses in the network and more active power.
This allows us to optimise on the system sizing.