What is an axial film capacitor?
An axial film capacitor is a type of capacitor that consists of two conductive electrodes separated by a thin insulating film, wound in a cylindrical shape with the leads extending from both ends of the cylinder. The insulating film can be made of various materials such as polyester, polystyrene, or polypropylene. Axial film capacitors are commonly used in electronic circuits as they have a low leakage current and high tolerance for temperature and frequency variations. They are also known for their high reliability, stability, and long lifespan. Axial film capacitors come in a wide range of capacitance values and voltage ratings, making them suitable for various applications such as power supplies, audio circuits, and filters.
How is an axial film capacitor made?
Axial film capacitors are electronic components that are used for storing and releasing electrical energy. They are made using a thin plastic film, which is coated with a metal layer on both sides. The process for making axial film capacitors typically involves the following steps:
Film Production: The plastic film is produced by extruding a thin sheet of polyethylene terephthalate (PET), polypropylene (PP), or polycarbonate (PC) material. The thickness of the film can vary, depending on the desired capacitance rating.
Coating: The film is coated with a thin layer of metal, such as aluminum or zinc, on both sides using a vacuum deposition process. The metal coating creates two conductive plates separated by a dielectric material (the plastic film).
Winding: The coated film is then wound into a cylindrical shape, with one end of each metal layer protruding to form the capacitor terminals.
Electrolyte filling: In some cases, the capacitor may be filled with an electrolyte to improve its performance.
Encapsulation: The wound capacitor is then encapsulated in a plastic or metal casing, which protects it from damage and provides a stable mounting structure.
Quality Control: The finished capacitor undergoes rigorous quality control testing to ensure that it meets the required specifications for capacitance, voltage rating, and temperature range.
Axial film capacitors are widely used in a variety of electronic applications, including power supplies, audio equipment, and motor control circuits. They are preferred for their high reliability, long lifespan, and low self-inductance.
Axial film capacitor datasheet
Here is an example of a datasheet for an axial film capacitor:
Capacitance: 1µF ±10%
Voltage Rating: 100VDC
Dielectric Material: Polyethylene Terephthalate (PET)
Capacitance Tolerance: ±10%
Operating Temperature Range: -40°C to +85°C
Dissipation Factor: 0.1% max @ 1kHz and 25°C
Insulation Resistance: 10,000 MΩ or 1000 s, whichever is less, at 25°C and 100VDC
Dimensions: 5mm x 11mm
Lead Spacing: 2.5mm
Lead Diameter: 0.6mm
Lead Length: 25mm
Encapsulation: Flame retardant epoxy resin
Suitable for pulse and high frequency applications
High stability and reliability
Self-healing properties to prevent catastrophic failure
How to test an axial film capacitor?
Here are the steps to test an axial film capacitor:
Before testing, ensure that the capacitor is discharged to prevent any potential electrical shock. You can do this by touching the capacitor's leads with a metal object like a screwdriver.
Use a multimeter to measure the capacitance of the capacitor. Set the multimeter to the capacitance measurement mode and connect the capacitor leads to the appropriate terminals on the multimeter. The capacitance value should be within the tolerance range specified on the capacitor.
Check the leakage current of the capacitor. To do this, set the multimeter to the current measurement mode and connect the capacitor leads in series with the multimeter. Apply a voltage that is lower than the capacitor's rated voltage and measure the current flowing through the capacitor. The leakage current should be very low or negligible.
Check the insulation resistance of the capacitor. Set the multimeter to the resistance measurement mode and connect the capacitor leads to the multimeter terminals. Apply a voltage that is lower than the capacitor's rated voltage for a specified time (usually a minute) and measure the resistance. The insulation resistance should be very high, ideally in the megaohm range.
Check the ESR (Equivalent Series Resistance) of the capacitor. This can be done using an ESR meter. Connect the capacitor to the ESR meter and read the value displayed on the meter. The ESR value should be within the tolerance range specified on the capacitor.
If any of the above tests fail, then the capacitor may be faulty and should be replaced.
Does an axial film capacitor have the polarity?
No, an axial film capacitor does not have polarity.
Film capacitors, including axial film capacitors, are generally non-polarized capacitors, which means that they can be connected to a circuit in either direction without causing damage or affecting their performance. This is because the construction of the capacitor involves the use of two metal films separated by a dielectric material, which does not have a specific polarity.
However, there are some types of film capacitors, such as electrolytic film capacitors, that can have polarity and must be connected to the circuit with the correct polarity. It's important to always check the datasheet or marking on the capacitor to determine if it is polarized or non-polarized before connecting it to a circuit.
What is difference between an axial film capacitor and an electrolytic capacitor?
Axial film capacitors and electrolytic capacitors are two different types of capacitors with different construction, characteristics, and applications. The main differences between them are:
Construction: Axial film capacitors are made of a thin plastic film that is coated with a metal layer on both sides. The metal layers are then wound together to form a cylindrical shape with axial leads. Electrolytic capacitors, on the other hand, have a metal foil as one electrode, and an oxide layer as the dielectric, formed by electrolytic action. This oxide layer is coated with a conductive electrolyte, and the whole assembly is then rolled into a cylindrical shape with radial leads.
Capacitance Range: Electrolytic capacitors generally have a higher capacitance range compared to axial film capacitors. While axial film capacitors typically range from a few picofarads (pF) to a few microfarads (uF), electrolytic capacitors can range from a few microfarads to several thousand microfarads.
Voltage Rating: Electrolytic capacitors typically have a higher voltage rating compared to axial film capacitors. While axial film capacitors typically have a voltage rating of up to a few hundred volts, electrolytic capacitors can have a voltage rating of several hundred volts or more.
Polarity: Electrolytic capacitors are polarized, meaning they have a positive and negative lead and must be connected correctly to function properly. Axial film capacitors are non-polarized, meaning they can be connected in any direction.
Temperature Stability: Axial film capacitors typically have better temperature stability than electrolytic capacitors, which can be affected by high temperatures.
Applications: Axial film capacitors are used in a wide range of applications, including audio equipment, signal filtering, and timing circuits. Electrolytic capacitors are commonly used in power supplies, audio equipment, and other applications where high capacitance and voltage ratings are required.
In summary, axial film capacitors and electrolytic capacitors have different construction, capacitance range, voltage rating, polarity, temperature stability, and applications. It is important to select the appropriate capacitor type based on the specific requirements of the circuit and the application.
What are the applications for axial film capacitors?
Axial film capacitors have a number of applications in various electronic circuits. Some of the common applications of axial film capacitors include:
Power electronics: Axial film capacitors are commonly used in power electronics, where they are used to store and discharge energy. They are commonly used in applications such as power supplies, inverters, and motor drives.
Audio circuits: Axial film capacitors are often used in audio circuits, where they are used to filter and smooth the signal. They are used in applications such as amplifiers, mixers, and equalizers.
Lighting: Axial film capacitors are also used in lighting applications, where they are used as part of ballast circuits in fluorescent and high-intensity discharge lamps.
Automotive electronics: Axial film capacitors are commonly used in automotive electronics, where they are used in ignition systems, power electronics, and other applications.
Communication systems: Axial film capacitors are also used in communication systems, where they are used in filters and other circuits to remove unwanted noise and interference.
Industrial applications: Axial film capacitors are also used in a variety of industrial applications, such as motor control, power conditioning, and power factor correction.
Overall, axial film capacitors are versatile components that are widely used in a variety of electronic circuits and applications.