Applications of capacitors
Capacitors are used by Dynamic Random Access Memory (DRAM) devices to represent binary information as bits.
Capacitors are commonly used in electronic devices to maintain power supply while batteries are being changed.
[1] In car audio systems, large capacitors store energy for the amplifier to use on demand.
An uninterruptible power supply (UPS) can be equipped with maintenance-free capacitors to extend service life.
Reservoir capacitors are used in power supplies where they smooth the output of a full or half wave rectifier.
Audio equipment, for example, uses several capacitors in this way, to shunt away power line hum before it gets into the signal circuitry.
Individual motor or lamp loads may have capacitors for power factor correction, or larger sets of capacitors (usually with automatic switching devices) may be installed at a load centre within a building or in a large utility electrical substation.
[1] High-pass filters have many uses, such as blocking DC from circuitry sensitive to non-zero average voltages or radio frequency devices.
If the inductance is large enough, the energy will generate an electric spark, causing the contact points to oxidize, deteriorate, or sometimes weld together, or destroy a solid-state switch.
Similarly, in smaller scale circuits, the spark may not be enough to damage the switch but will still radiate undesirable radio frequency interference (RFI), which a filter capacitor absorbs.
Snubber capacitors are usually employed with a low-value resistor in series, to dissipate energy and minimize RFI.
Low ESR (equivalent series resistance) electrolytes are often required to handle the high ripple current.
Mains filter capacitors are usually encapsulated wound-plastic-film types, since these deliver high voltage rating at low cost, and may be made self-healing and fusible.
Computers use large numbers of filter capacitors, making size an important factor.
Once in application solid tantalum capacitor performance will improve over time and the chances of a failure due to component mis-manufacturing decrease.
When the rotor comes close to operating speed, a centrifugal switch (or current-sensitive relay in series with the main winding) disconnects the capacitor.
There are also capacitor-run induction motors which have a permanently connected phase-shifting capacitor in series with a second winding.
Capacitors can be used in analog circuits as components of integrators or more complex filters and in negative feedback loop stabilization.
Industrial pressure transmitters used for process control use pressure-sensing diaphragms, which form a capacitor plate of an oscillator circuit.
Some accelerometers use microelectromechanical systems (MEMS) capacitors etched on a chip to measure the magnitude and direction of the acceleration vector.
Capacitive touch switches are now used on many consumer electronic products A capacitor can possess spring-like qualities in an oscillator circuit.
Service procedures for electronic devices usually include instructions to discharge large or high-voltage capacitors.
Capacitors may also have built-in discharge resistors to dissipate stored energy to a safe level within a few seconds after power is removed.
High-voltage capacitors are stored with the terminals shorted, as protection from potentially dangerous voltages due to dielectric absorption.
High-voltage capacitors may catastrophically fail when subjected to voltages or currents beyond their rating, or as they reach their normal end of life.
