A paper capacitor is among the earliest capacitors. It is also known as a condenser because it is constructed using two conducting surfaces separated by an insulating material. Paper capacitors are also known by the name fixed capacitors, in which paper is used as the dielectric material that stores energy as the electric field. These capacitors are mainly operated at powerline capacity with a capacitance value ranging from 1nF to 1uF. A paper capacitor holds a set amount of electric charge. Then the construction of this capacitor is determined by the paper used, which is classified into two types known as:
- Paper sheet
- Metalized paper
How Does a Paper Capacitor Work?
As mentioned before, a paper capacitor is constructed of two metallic plates and paper as their dielectric used between those plates. The plates are positive and negative. When you apply even a tiny amount of electric charge to the plates, the positive charge will be attracted to one plate and the negative to the other. The electrical energy is used when the capacitor discharges. They are found in the range of 500pF to 50nF. Paper capacitors are also good at providing high leakage current.
Applications of Paper Capacitors
- Paper capacitors are effectively used in various applications like:
- High current and high voltage applications
- Used effectively in electronics and electrical applications
- They are used in power conditioning systems which helps in blocking DC signals and allows AC signals
- Used in-car audio systems which improve the overall sound quality of the speakers
- Utilised as sensors to measure fuel levels, air humidity, and mechanical strain levels.
- Also effectively used in the signal coupling, noise filtering, remote sensing, and decoupling systems.
- They are widely used in signal processing systems like dynamic random-access memory, speakers, tune circuits, analog equalisers, and radio receivers.
Construction of Paper Capacitors
As we previously mentioned, the construction of the paper capacitor can be divided into two types that are:
- Paper sheet capacitor
- Metalized paper capacitor
Paper Sheet Capacitor
In constructing this capacitor, an aluminium sheet and a paper sheet are required. The paper sheet is then covered with wax or soaked in oil to protect it from environmental factors. Paper capacitors store a fixed amount of electric charge at a fixed capacitance value. The paper sheet placed between the aluminium sheet will function as the dielectric material, and the aluminium will serve as the electrodes.
As we all know, paper is terrible at conducting electricity, which restricts the flow of electric current between the aluminium sheets, which allows the electric field to pass through it and functions as a barrier to the electric current. The aluminium sheets and paper sheets are folded in a cylinder shape. The whole cylinder is covered with plastic resin or wax to protect it from environmental factors, especially moisture. The two-wire leads are usually taken from the ends of the aluminium sheets.
Metallised Paper Capacitor
In a metallised paper capacitor, the paper is used as dielectric material and coated with a thin layer of aluminium or zinc rolled in the form of a cylinder. The exact process happens in this one for protection against environmental factors, which is coating with wax. These capacitors are usually coated with zinc because chemical actions can quickly destroy them. Therefore, they are widely used in construction. There is also a difference in size as these capacitors are comparatively smaller than paper sheet capacitors.
