Capacitor in series and its applications

What is a capacitor and its unit

A capacitor is a passive electronic component or a condenser, a capacitor consists of a pair of conductors and the conductors are separated by a dielectric. If there is a potential difference present across the conductors then there will be an electric field present in the dielectric. The dielectric may be air, paper or any other material which has high insulative properties, the electric which is in dielectric can store energy and it produces a mechanical force between the conductors. The effect will be high if there is a small separation between a large area of conductors and because of this the capacitor conductor is called plates. Capacitors can be used in circuits to block the flow of DC and it allows the flow of AC, it can also be used to filter out interference and can smooth the output of power supplies and the capacitor unit is the farad.


How does a capacitor works

Capacitors and batteries working are related in a way both stores electrical energy a battery produces electrons by chemical reaction while the capacitor doesn’t produce electrons it only stores them. If a charge is applied to one of the conductors it will exert a force on the charge carriers of the other conductor, Attracting opposite polarity charge and repels on the same polarity. A charge will be formed at the surface of the conductor and thus it holds equal and opposite charges on the facing surface and an electric field will be developed by the dielectric.

What is capacitance

The capacitance of a capacitor can be defined as the ratio of the amount of charge that is on the capacitor to the potential difference between the plates at this point, and the capacitance is only depended upon the geometry of the capacitor. Capacitance can also be defined as the ability of the capacitor to store charge. Capacitance is the charge on the plates of a capacitor per unit voltage across the plates of a capacitor.

C = Q/V

What are the physical factors that influence the capacitance of a capacitor

There are three major physical characteristics that the capacitance of a capacitor depended on they are

  • The distance of the plate
  • Area of overlap
  • The permittivity of the dielectric

The concentration of the charge on the capacitor plates can be increased by increasing the conservation of electric field intensity between the plates. If the distance between the charged plate is small then the loss of the electric field at the edges between the plates would be less. If the area of overlap between the plates is larger, then the electric field will be larger between the parallel plates of the capacitor, and because of that, the capacitance will be high. To get a better capacitance the dielectric material should have good permittivity and very low permeability.

what is a series capacitor

In order to obtain the required capacitance, value capacitors are combined either in series or in parallel. Series connected capacitors will always have the same charge but they don’t have the same voltage unless the capacitors have the same capacitance.

The total capacitance of the series combination is less than the capacitance of any individual capacitor and its reason is that the series combination acts as a single capacitor, with a separation between the plates equal to the sum of separations of the individual capacitors. The larger the separation between the plates the lower the capacitance. Series capacitor compensates line reactance if the total line reactance is high series capacitors are very effective and has better stability. A series capacitor is an automatic voltage regulator. By using series capacitor reduction in line current is small as it compensates only for line inductance.

Capacitors are combined in series to get higher working voltage, some safety precautions must be taken for high energy storage capacitor in series, to make sure that the failure of one capacitor and leaking current will not apply too much voltage to the other series capacitors. The capacitors which are connected in series all have the same current so each capacitor can store the same amount of charge

The charge stored at each capacitor is

Q total = Q1 = Q2 =Qn

Q total is the total amount of charge

Q1 and Qn are the charges at the individual capacitor

The charges at each capacitor are equal and the total charge is equal to the individual charge, it is because when the voltage is applied to the capacitors charge shift occurs and electrons are carried from one plate of each capacitor to the other, it shows that the charge stored by the plate of capacitor has come from the adjacent capacitor’s plate and it shows that the charge carriers have simply shifted through all the capacitors and that’s the reason why charges in each capacitor is equal.

How series capacitors can be useful for transmission lines

Series capacitors are used in transmission lines for effectively compensate for the inherent inductance in the line to lower the total impedance. The series capacitor is placed in series with the line, this allows the circuit to transfer more energy with less heating of the lines. The series capacitors are used at either end of the transmission lines. In certain cases, they are used near the middle of the transmission line section which reduces the worst-case potential fault current.

What is the protection needed for series capacitor

  • Unbalanced protection
  • Spark gap protection
  • Short circuit protection
  • Non-linear resistor protection

What are the applications of a capacitor

Energy storage

• Used for pulsed power application

• Power conditioning

• Power factor correction

• Suppression and coupling

• Used as motor starters

• Used in the oscillator to control the frequency

• Used to decouple one part of the circuit from other

• Used in active and passive filters

• Reduce ripple and regulates DC

• Block DC and pass AC