Film Capacitors

Polypropylene (PP) film capacitors are a common capacitor used in electrical equipment. They are made of two pieces of thin plastic film, charged with electrodes as the dielectric. They can replace electrolytic capacitors in applications where the voltage is above 500V.

RS carries a great range of capacitors including these polypropylene film capacitors in various capacitance, voltage ratings and tolerances for all your electronics needs.

Different Types of Polypropylene (PP) Film Capacitors

There are two main formats of polypropylene film capacitors. They can be recognised by the type of dielectric (insulating) material used. To get the desired electrical characteristics you need, such as stability or ability to withstand high voltage, you can choose different film materials for the dielectric layer.

Film/Foil Capacitors

Film/foil capacitors feature two metal foil electrodes sandwiched between two layers of polypropylene plastic film. This configuration offers high stability and excellent capacitance retention under high voltages, making them ideal for demanding applications.

Metallised Film Capacitors

Metallised film capacitors have a thin layer of metal deposited directly onto the polypropylene film, acting as the electrodes. This design results in smaller and lighter capacitors compared to film/foil types. They are suitable for general-purpose applications where size and weight are considerations.

Benefits of Film Capacitors

High Stability

Film capacitors are known for their exceptional capacitance stability. This means their capacitance value remains consistent even when subjected to fluctuations in temperature and frequency. This stability is crucial in applications where precision and reliability are paramount, such as in timing circuits, filters, and oscillators.

Low Dielectric Loss

Film capacitors exhibit low dielectric loss, which translates to minimal energy dissipation in the form of heat. This low loss characteristic makes them highly efficient in power electronics and high-frequency circuits, where energy efficiency is critical.

Excellent Frequency Response

Due to their construction and materials, film capacitors possess excellent frequency response. They can handle high-frequency signals with minimal distortion, making them ideal for applications like filters, resonant circuits, and snubbers in switching power supplies.

Film Capacitor Applications

• Switching Power Supplies: Film capacitors, particularly DC-link film capacitors, are essential components in switching power supplies. They help filter and smooth the DC voltage output, reducing ripple and ensuring a stable power supply for sensitive electronic devices.
• High-Voltage Circuit Applications: Film capacitors, including power film capacitors, are well-suited for high-voltage applications due to their high dielectric strength. They can withstand significant electrical stress, making them reliable choices for circuits operating at elevated voltages.
• Lighting Ballast Systems: In lighting ballasts, AC film capacitors play a vital role in regulating current and voltage. They help ensure optimal performance and longevity of lighting systems, whether in residential, commercial, or industrial settings.
• AC/DC Filtering: Film capacitors are commonly used for filtering in both AC and DC circuits. In AC film capacitors, they help remove unwanted noise and harmonics from the power line, while in DC film capacitors, they smooth out voltage ripples for clean and stable power delivery.
• Audio Signal Coupling and Blocking: Audio circuits often utilise film capacitors for coupling and blocking purposes. They allow AC audio signals to pass while blocking unwanted DC components, preserving the integrity of the audio signal.

How to Choose the Right Film Capacitor for Your Needs

Selecting the right film capacitor involves considering these factors:

AC vs. DC Application

• AC Applications: Film capacitors designed for AC applications are built to handle the constantly reversing polarity of AC voltage. These capacitors are often non-polarised, meaning they can be connected in either direction. They're commonly found in lighting ballasts, motor run circuits, and other applications where the voltage alternates direction.
• DC Applications: Film capacitors designed for DC applications are specifically engineered for the unidirectional flow of DC voltage. They often have a polarity marking and must be connected with the correct polarity to avoid damage. These capacitors are frequently used in power supplies, filtering circuits, and other applications where the voltage remains constant in one direction.

Material Selection

• Polypropylene (PP): Offers high stability and low dielectric loss, making it suitable for various applications.
• Polyester (PET): Provides good capacitance stability and is often used in general-purpose applications.
• Polyethylene Naphthalate (PEN): Offers a higher temperature tolerance than PP or PET film capacitors, making it suitable for demanding environments.
• Polytetrafluoroethylene (PTFE): Exhibits excellent high-frequency performance and stability, but is more expensive.

How to Order Film Capacitors from RS

RS offers a wide range of film capacitors from trusted manufacturers like Ducati Energia, EPCOS, KEMET, NISSEI, and Panasonic, ensuring you find the right fit for your electronic projects. To order film capacitors from RS, browse our comprehensive online catalogue, select the desired items, and add them to your cart.

How Delivery Works at RS Hong Kong

RS Hong Kong is committed to providing efficient delivery services for our film capacitors, aluminium capacitors, RCBOs, MOSFET transistors, and other components. We offer a range of delivery options to suit different business needs. For more details, please visit ourDelivery Information page.