Equivalent Series Resistance - Component Models - Capacitors

Capacitors

In a non-electrolytic capacitor the metallic resistance of the leads and electrodes and losses in the dielectric cause the ESR. Typically quoted values of ESR for ceramic capacitors are between 0.01 and 0.1 ohms. ESR of non-electrolytic capacitors tends to be fairly stable over time; for most purposes real non-electrolytic capacitors can be treated as ideal components.

Aluminium and tantalum electrolytic capacitors have much higher ESR values, up to several ohms, and ESR tends to increase with frequency due to effects of the electrolyte. A very serious problem, particularly with aluminium electrolytics, is that ESR increases over time with use; ESR can increase enough to cause circuit malfunction and even component damage, although measured capacitance may remain within tolerance. While this happens with normal aging, high temperatures and large ripple current exacerbate the problem. In a circuit with significant ripple current, an increase in ESR will increase heat dissipation, thus accelerating aging.

Electrolytic capacitors rated for high-temperature operation and of higher quality than basic consumer-grade parts are less susceptible to become prematurely unusable due to ESR increase. A cheap electrolytic capacitor may be rated for a life of less than 1000 hours at 85°C (a year is about 9000 hours). Higher-grade parts are typically rated at a few thousand hours at maximum rated temperature, as can be seen from manufacturers' datasheets. Electrolytics of higher capacitance have lower ESR; if ESR is critical, specification of a part of larger capacitance than is otherwise required may be advantageous.

Polymer capacitors usually have lower ESR than wet-electrolytic of same value, and stable under varying temperature. Therefore polymer capacitors can handle higher ripple current. From about 2007 it became common for better-quality computer motherboards to use only polymer capacitors where wet electrolytics had been used previously.

The ESR of capacitors of relatively high capacity (from about 1 μF), which are the ones likely to cause trouble, is easily measured in-circuit with an ESR meter.

Read more about this topic:  Equivalent Series Resistance, Component Models

Other articles related to "capacitors, capacitor":

Applications Of Capacitors - Hazards and Safety
... Capacitors may retain a charge long after power is removed from a circuit this charge can cause dangerous or even potentially fatal shocks or damage connected equipment ... such as a disposable camera flash unit powered by a 1.5 volt AA battery contains a capacitor which may be charged to over 300 volts ... devices usually include instructions to discharge large or high-voltage capacitors ...
Motor Capacitor - Start Capacitors
... Start capacitors above 20 microfarads (µF) are always non-polarized Aluminum Electrolyic Capacitors with non solid electrolyte and therefore they are only applicable for the short motor starting time ... Start capacitors briefly increase motor starting torque and allow a motor to be cycled on and off rapidly ... Start capacitors have ratings above 70 microfarads (µF), with four major voltage classifications 125 V, 165V, 250 V, and 330 V ...
Motor Capacitor - Run Capacitors
... Run capacitors are mostly polypropylene film capacitors and are designed for continuous duty, and they are energized the entire time the motor is running ... Run capacitors are rated in a range of 1.5–100 microfarads (µF or mfd), with voltage classifications of 370 V or 440 V ... Single phase electric motors need a capacitor to energize a second-phase winding ...
Types Of Capacitor
... This article is about the commercial discrete capacitors as customary components for use in electronic equipment ... For the physical phenomenon, see Capacitor ... Capacitors, together with resistors, inductors and memristors, belong to the group of "passive components" for electronic equipment ...
Silver Mica Capacitor - Types - Silvered Mica Capacitors
... Commonly known as silver mica capacitors, these rendered clamped mica capacitors obsolete ... can be thinner No clamping mechanism is needed Silvered mica capacitors are one of the less popularly used types due to their high cost ... They are sometimes informally referred to as mica capacitors ...