What Is Capacitor:
A capacitor is a device used to store electrical energy. It consists of two or more metal plates separated by an insulating material, such as air, wax, paper, plastic, or even vacuum. When a voltage is applied across the plates, an electric field is created that stores energy in electric fields.
Capacitors are found in various electronic devices, including televisions, computers, and cell phones. They are also used in industrial applications such as motor starters and power factor correction. In addition, capacitors are used in many electrical circuits, including filters and oscillators.
The size of a capacitor is measured in farads (F). One farad is the equivalent of storing one joule of energy per volt. Most capacitors used in electronic devices range from microfarads (μF) to picofarads (pF).
Capacitors are often classified by their construction. The most common types are:
These capacitors use a liquid electrolyte to store energy. The electrolyte is in contact with two metal plates, and when a voltage is applied, the electrolyte ionizes and creates an electric field. This field stores energy between the plates. Electrolytic capacitors are often used in power supplies and inverters.
These capacitors use a thin film of metallic oxide as the insulating material. When a voltage is applied, this film conducts electricity. Film capacitors are often used in circuits that require a high-frequency response, significant changes in voltage, or low insulation resistance.
These capacitors use ceramic as the insulating material. They are usually small and have a wide range of electrical values. Ceramic capacitors are generally used for high-frequency applications where their self-resonance is an advantage.
-Tantalum electrolytic capacitor:
A type of electrolytic capacitor made from tantalum metal. Tantalum has a higher working voltage than aluminum. It can dissipate more heat before failing, making it useful for limited life applications such as automobile ignition systems and camera flash units…
A type of capacitor that can store a large amount of energy in a small package. Supercapacitors are typically used to provide short bursts of energy, such as in motor starting or backup power supplies.
Some specialized capacitors, such as the Varistor and Gas Discharge Tube.
The capacitance of a capacitor is determined by the size of the plates, the distance between the dishes, and the dielectric material separating the leaves. The capacitance value is usually expressed in farads (F), microfarads (μF), or picofarads (pF).
The voltage rating is the maximum voltage that can be applied without causing it to fail. Capacitors are usually assigned a voltage rating of 50, 100, 200, 350, 500, or 600 volts.
The tolerance of a capacitor is the percentage difference between the actual capacitance value and the advertised value…
The temperature coefficient refers to how much it changes its electrical properties based on surrounding temperatures. Temperature coefficients can be positive or negative, but they are generally optimistic when operating below 80°C (176°F). For example, most capacitors’ temperature coefficients may be +80 parts per million (ppm) per degree centigrade (-60°F to 140°F).
Therefore if your working environment varies from -50°C to 85°C (-58F to 185°F), the capacitor’s capacitance value may vary up to plus or minus 16% from its nominal value.
The life of a capacitor is the length of time it can be expected to function without fail. The life of a capacitor is usually expressed in terms of hours, minutes, or seconds. The life of a capacitor is determined by the type of capacitor, the operating conditions, and the environment.
There are a variety of factors that can affect the operation of a capacitor:
-Voltage: The voltage applied to a capacitor affects its capacitance value and how much energy it can store.
-Temperature: Higher temperatures cause a decrease in capacitance value and an increase in leakage current. In general, capacitors should be derated by 0.75% for every degree centigrade above 25°C (77°F).
-Humidity: Higher humidity levels can have a negligible effect on capacitance value, leakage current, and dissipation factor.
The life of a capacitor is related to the voltage applied to it and its temperature. In general, as the operating temperature or voltage increases, the life expectancy decreases. Conversely, like the temperature or voltage decreases, life expectancy increases.
Maximizing Capacitor Life
To obtain maximum capacitor life, follow these guidelines:
-Carefully select your application so that working voltage and temperature are within acceptable limits for your capacitor’s rated values. Design your circuit to use a capacitor with a voltage rating of more significant than the maximum expected voltage.
-Use capacitors rated for continuous service, not impulse service.
-Maximize heat dissipation by using large, closely spaced solder tabs and good copper traces on your component or PCB layout. This will prevent overheating that can result in capacitor failure.
-Minimize high temperature operating conditions by using ceramic capacitors with a -55°C to 85°C (-67°F to 185°F) working temperature range.
-Use high-quality components made from materials resistant to temperature, humidity, and other environmental hazards. Use X7R or Y5V dielectric material if applicable. For electrolytic capacitors, avoid high humidity and temperature conditions.
-Do not apply voltage to capacitors rated or more than their initial working voltage for more than one minute.
-Apply only the reverse polarity indicated by the dot marking on the capacitor’s positive terminal.
-Use a capacitor equal to or greater than the minimum required value. This will increase its service life and reliability.
-Keep your circuit free from solder flux, which can create leakage currents in tantalum capacitors. If necessary, clean change from your work area with acetone before soldering components in place.
For best results, do not use water-based solvent cleaners when cleaning around sensitive electronic components such as tantalum capacitors with solid gold terminations.
-Handle electrolytic capacitors carefully. The impedance between the capacitor’s anode and cathode can increase after some time due to impurities that may be present on the capacitor’s exposed electrode surfaces.
This increased impedance reduces the capacitor’s ability to store energy and dramatically shortens its service life. If you find a tantalum capacitor degrading, remove it from your design and replace it with a good quality equivalent part.