Paper capacitors are a type of electronic component that uses paper as a dielectric material to store electrical charge and consist of two conductive plates separated by a thin layer of paper.
The capacitance value is determined by the surface area of the plates, the distance between them, and the type of paper used. While they have largely been replaced by other types of capacitors in modern electronics, paper capacitors are still used in certain applications where their unique properties make them the best choice.
Features of Paper Capacitor
- Paper capacitors use paper as the dielectric material to store electrical charge.
- They are relatively low-cost and have good long-term stability.
- They can withstand high voltage levels due to the high dielectric strength of the paper material.
- They have good high-frequency characteristics, making them useful in radio frequency (RF) circuits.
- They tend to be physically large, which can make them difficult to use in compact electronic designs.
- They have a higher internal resistance than some other types of capacitors.
Types of Paper Capacitor
Some common types are:
- Rolled paper capacitor
- Impregnated paper capacitor
- Metalized paper capacitor
- Oil-filled paper capacitor
- Paper/polyester capacitor
- Wax-paper capacitor
- Foil-paper capacitor
Rolled Paper capacitor
This is the most common type of paper capacitor, consisting of a paper dielectric rolled between two strips of aluminum foil.
Impregnated Paper capacitor
This type of capacitor has the paper dielectric impregnated with an insulating oil or wax, which increases its dielectric constant and reduces the likelihood of breakdown.
Metalized Paper capacitor
This type of capacitor uses a thin layer of metal deposited directly onto the paper dielectric as one of the conductive plates.
Oil-filled Paper capacitor
In this type of capacitor, the paper dielectric is impregnated with oil and enclosed in a metal canister. Oil-filled paper capacitors are commonly used in high-voltage applications.
Paper/polyester capacitors
These capacitors use both paper and polyester film as the dielectric material, resulting in a capacitor with the advantages of both materials.
Wax-Paper capacitor
A wax-paper capacitor is a type of paper capacitor in which the paper dielectric is impregnated with a wax material to improve its insulation properties. The wax helps to protect the paper from moisture and increase its dielectric strength.
Foil-Paper capacitor
A foil-paper capacitor is a type of paper capacitor in which thin strips of metal foil are sandwiched between layers of paper dielectric. The metal foil serves as the conductive plates of the capacitor, while the paper provides the insulation between the plates.
Working of Paper Capacitor
A paper capacitor works by storing electrical charge between two conductive plates separated by a dielectric material, which is made of a layer of paper. When a voltage is applied to the capacitor, an electric field is created across the dielectric material, causing electrons to accumulate on one of the plates, while an equal number of electrons are repelled from the other plate.
The capacitance of the paper capacitor is determined by the surface area of the metal plates, the distance between them, and the dielectric constant of the paper. When the voltage is removed from the capacitor, the stored charge is released, and the capacitor discharges.
Applications of Paper Capacitor
Some common applications of paper capacitors are:
Power supply filtering:
Paper capacitors are commonly used in power supply circuits to filter out high-frequency noise and ensure stable DC voltage output.
Audio circuits:
Paper capacitors are widely used in audio circuits as coupling capacitors to pass AC signals while blocking DC signals.
Motor starting and run capacitors:
Paper capacitors are used in single-phase AC motors for starting and running purposes.
High-voltage circuits:
Paper capacitors with high voltage ratings are used in high-voltage circuits such as in CRT displays, voltage multipliers, and Tesla coils.
Lighting circuits:
These capacitors are used in lighting circuits such as fluorescent and high-intensity discharge lamps for power factor correction
Pulse circuits:
These types of capacitors are used in pulse circuits for energy storage and discharge applications.