21FB4425

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Film capacitors, also known as plastic film capacitors, are electrochemical capacitors with an insulating plastic film as the dielectric. They are divided into three groups including polyester film capacitors, polypropylene film capacitors, and polycarbonate film capacitors. An example of the film capacitors is the 21FB4425 model, which has a capacity of 450V-25uF and is suitable for AC power applications.

Application Field

The 21FB4425 is one of the most popular AC power film capacitors from Progreen. It features excellent self-healing characteristics and a high safety factor, making it ideal for motor applications. This model also features low dissipation factor which assists to minimize noise and ensure quality of sound output. The capacitor is designed for indoor applications such as for fan motors, compact fluorescent lamp ballasts (CFLs), and inductive loads such as motors, pumps, and engines.

The 21FB4425 is also suitable for power factor correction (PFC) applications. This capacitor works well to improve the power quality in commercial, industrial and residential installations as it is able to reduce harmonic currents from inductive loads.

It is also suitable for filtering applications. With its low dielectric loss factor, it is suitable for attenuating high frequencies for the purpose of reducing audible noises in AC/DC applications which require unidirectional current flow.

Working Principle

The working principle of the 21FB4425 is based on the law of capacitance, which states that the capacitance of a capacitor is directly proportional to the ratio of the surface area of the anode and cathode divided by the distance between them.

The 21FB4425 is an aluminum electrolytic capacitor which has two electrodes - an anode and a cathode, separated by a thin insulating plastic film. As a current flows through the capacitor, the anode and cathode attract and repel, generating an electric field which determines capacitance. When an AC current passes through the capacitor, the expansion and contraction of the dielectric material stores and releases energy, allowing for the current to flow through.

The 21FB4425 also features a self-healing capability which works according to the same principle of capacitance. When faults and partial discharge occur along the dielectric material, an electrical breakdown is triggered and the breakdown current flows through the fatty acids on the anode and cathode. This creates a localized heat that improves the insulation of the dielectric film, thus restoring the capacitor.

The 21FB4425 film capacitor is a reliable and long-lasting choice for a variety of AC power applications, from motor drives to power factor correction. It is important to make sure that the breakdown voltage and capacitance values are suitable for the application when selecting the capacitor, as this will ensure optimal performance with minimal risk of failure.

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