Capacitors have many uses in electronic and electrical systems. They are everywhere so rarely do electrical products exclude at least one for some purpose.
Video Applications of capacitors
Energy storage
A capacitor can store electrical energy when connected to its charging circuit. And when disconnected from its charging circuit, it can eliminate stored energy, so it can be used like a temporary battery. Capacitors are generally used in electronic devices to maintain power supplies while batteries are being changed. (This prevents the loss of information in volatile memory.)
Conventional electrostatic capacitors provide less than 360 joules per kilogram of energy density, while capacitors using emerging technologies can provide more than 2.52 kilojoules per kilogram.
In car audio systems, large capacitors store energy for amplifiers to use on demand.
Uninterruptible power supply (UPS) can be equipped with maintenance-free capacitors for extended life.
Maps Applications of capacitors
Power and pulsed weapons
Large, specially constructed groups, low-voltage low inductance capacitors ( bank capacitors ) are used to supply large current pulses for many pulsed power applications. These include electromagnetic formation, Marx generators, pulsed lasers (mainly TEA lasers), pulse-forming networks, fusion research, and particle accelerators.
Large capacitor banks (reservoirs) are used as energy sources for exploding bridgewire detonators or slapper detonators in nuclear weapons and other special weapons. Experimental work is underway using a capacitor bank as a resource for electromagnetic armor and electromagnetic railgun or coilgun.
Conditioning
The reservoir capacitors are used in the power supply where they transmit a full or half wave rectifier output. They can also be used in charge pump circuits as energy storage elements in voltage generation higher than the input voltage.
The capacitor is connected in parallel with the DC power circuit of most electronic devices to smooth the current fluctuations for the signal or control circuitry. Audio equipment, for example, uses multiple capacitors in this way, to avoid humming power lines before entering the signal circuitry. The capacitor acts as a local reserve for a DC power source, and cuts the AC current from the power supply. This is used in car audio applications, when rigid capacitors compensate for inductance and lead resistance to lead-acid car batteries.
Power factor correction
In power distribution, capacitors are used for power factor correction. Such capacitors often come as three capacitors are connected as three-phase electrical charges. Typically, these capacitor values ​​are given not in farads but as reactive power in reactive volt-amperes (VAr). The objective is to resist the inductive loading of devices such as induction motors, electric motors and transmission lines to make the load appear mostly resistive. The individual motor or lamp loads may have capacitors for power factor correction, or larger set of capacitors (usually with automatic switching devices) can be installed in the load center inside the building or in large utility powerhouses. In a high-voltage direct current transmission system, the power factor correction capacitor may have a tuning inductor to suppress the harmonic current which would otherwise be injected into the AC power system.
Suppression and coupling
Signal coupling
Because capacitors pass AC but block DC signals (when charged to DC voltage applied), they are often used to separate AC and DC components from a signal. This method is known as AC coupling or "capacitive coupling". Here, the large value of the capacitance, whose value does not need to be controlled accurately, but the small reactance at the signal frequency, is used.
Decoupling
A decoupling capacitor is a capacitor that is used to separate one part of a circuit from another. Noise caused by other circuit elements is smoothed through the capacitor, reducing the effect they have on the rest of the circuit. It is most commonly used between power supply and ground. The alternate name is the bypass capacitor because it is used to bypass the power supply or other high impedance components of a circuit.
High-pass and low-pass filters
Filter and snubber voice
When the inductive circuit is opened, the current through the inductance collapses quickly, creating a large voltage across the open circuit of the switch or the relay. If the inductance is large enough, the energy will generate an electric spark, causing the point of contact to oxidize, deteriorate, or sometimes merge together, or destroy a solid-state switch. The snubber capacitors on the newly opened circuitry create a way for this drive to pass through the contact points, thus preserving their lives; this is commonly found in contact breaker contact systems, for example. Similarly, in smaller scale circuits, the spark may not be sufficient to damage the switch but will still emit undesired radio frequency interference (RFI), which is absorbed by the filter capacitor. Snubber capacitors are typically used with low-value resistors in series, to dissipate energy and minimize RFI. The combination of such resistors is available in one package.
Capacitors are also used in parallel to interrupt the high-voltage circuit breaker unit to distribute the tension between these units. In this case they are called capacitor grading.
In a schematic diagram, a capacitor used primarily for DC charge storage is often drawn vertically in circuit diagrams with lower, more negative plates, drawn as arcs. The straight plate shows the positive terminal of the device, if polarized (see electrolytic capacitor).
Starter motor
In a single-phase squirrel cage motor, the primary winding within the motor housing is unable to initiate rotational motion on the rotor, but is capable of maintaining one. To start the motor, the secondary winding is used in series with the non-polarized initial capacitor to introduce the lag in the sinusoidal current through the initial winding. When the secondary winding is placed at an angle with respect to the primary winding, a rotating electric field is created. The rotation field force is not constant, but it is enough to start the rotor spinning. When the rotor approaches the speed of operation, centrifugal switch (or sensitive current release in series with the main winding) disconnects the capacitor. Start capacitors are usually mounted to the motor home side. This is called the start-capacitor motor, and has a relatively high initial torque.
There is also a capacitor-run induction motor that has a permanent phase-shift capacitor connected in series with a second winding. This motor is like a two phase induction motor.
Start motor capacitors are usually a non-polarized electrolytic type, while running capacitors are conventional paper or plastic film dielectric types.
5. Signal processing. The energy stored in the capacitor can be used to represent information, whether in binary form, as in DRAM, or in analog form, as in analog sample filters and CCD of Charge-coupled devices. Capacitors can be used in analog circuits as a more complex integrator or filter component and stabilization of negative feedback loops. The signal processing circuit also uses a capacitor to integrate the current signal.
Setting up the circuit
Capacitors and inductors are applied together in series that are set to select information in a particular frequency band. For example, the radio receiver depends on the variable capacitor to adjust the station frequency. Speakers use a passive analog crossover, and analog equalizer uses capacitors to select different audio bands.
Sensing
Most capacitors are designed to maintain a fixed physical structure. However, various factors may alter the structure of the capacitor; changes in capacitance can be used to sense these factors.
Changing the dielectric
The effects of various dielectric characteristics can also be used for sensing and measurement. Capacitors with open and porous dielectric can be used to measure moisture in the air. Capacitors are used to accurately measure fuel levels in an aircraft; as fuel covers more than a pair of plates, increased circuit capacitance.
Change the distance between the plates
Capacitors with flexible plates can be used to measure tension or pressure or weight.
Industrial pressure transmitters used for process control use sensor-sensing diaphragms, which form the capacitor plates of the oscillator circuit. The capacitor is used as a sensor in a condenser microphone, where one plate is driven by air pressure, relative to the fixed position of the other plate. Some accelerometers use microelectromechanical systems (MEMS) capacitors etched on a chip to measure the magnitude and direction of vector acceleration. They are used to detect acceleration changes, eg. as a tilt sensor or to detect a free fall, as the sensor triggers the spread of airbags, and in many other applications. Some fingerprint sensors use capacitors.
Changing the effective area of ​​the slab
Capacitive touch switches are now used in many consumer electronics products.
Oscillators
Capacitors can have spring-like qualities in oscillator circuits. In the example image, a capacitor acts to affect the biasing voltage on the base of the npn transistor. The resistance value of the voltage divider resistor and the capacitance value of the capacitor together control the oscillation frequency.
Dangers and security
Capacitors can retain the old charge after power is removed from the circuit; this charge may cause harmful or potentially fatal shocks or damage to connected equipment. For example, even seemingly harmless devices such as disposable flash flash units powered by AA 1.5 volt batteries contain capacitors that can be charged up to more than 300 volts. This is easily able to surprise. Service procedures for electronic devices typically include instructions for releasing large or high voltage capacitors. The capacitor may also have a built-in discharge resistor to remove stored energy to a safe level within a few seconds after power is released. High voltage capacitors are stored with short circuit terminals, as protection from potentially harmful tensions due to dielectric absorption.
Some old capacitors contain oils containing polychlorinated biphenyls (PCBs). It is known that PCB waste can leak into groundwater under landfill. Capacitors containing PCBs are labeled as containing "Askarel" and some other trade names. PCB-filled capacitors are found in very old fluorescent lamp bulbs (pre 1975), and other applications.
High voltage capacitors can fail catastrophically when they experience voltage or current outside their rating, or when they reach the end of normal life. The failure of dielectric or metallic interconnects can create curves that evaporate dielectric fluid, which results in protruding, bursting, or even explosive cases. Capacitors used in RF or continuous high current applications can become overheated, especially in the center of the capacitor windings. Capacitors used in high-energy capacitor banks can explode greatly when short capacitors cause sudden energy discharges stored in the rest of the bank into failed units. High voltage vacuum capacitors can produce soft X-rays even during normal operation. Proper containment, fusion, and preventive maintenance can help minimize this danger.
High voltage capacitors can benefit from pre-charging to limit the current of the heavy current at the up-power of the high-current direct current circuit (HVDC). This will extend component life and can reduce high voltage hazards.
References
Source of the article : Wikipedia
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