Capacitor Features

The properties of the capacitor define its temperature, voltage temperature and capacitance range, as well as its use in a particular application.

Amazing array associated with standard capacitorThere are capacitor features and specifications, and reading information printed on the body of a capacitor can sometimes be difficult to understand, especially when colors or numeric codes are used.

Eachthe capacitor family or type, some systems are easy to understand and others use misleading letters, colors or symbols to create their own uniquethe capacitor uses the properties and identification system.

By looking at the labelthe best way to understand the characteristics of the capacitor is to firstthe capacitor is to find out what kind of family it belongs to whether it is ceramic, film, plastic or electrolytic, and from this specialcapacitor properties may be easier to identify.

TwoAlthough the capacitor has exactly the same capacitance value, they can have different voltage ratings.A higher nominal voltageif a smaller nominal voltage capacitor is replaced, the increased voltage may damage the smaller value capacitor.

We also remember from the last lesson that with the polarized electrolytic capacitor, the positive end must go to the positive connection and the negative end to the negative connection, otherwise it may be damaged again.Therefore, it is always better to replace an old or damaged capacitor with the same type as indicated.Below is an example of capacitor markings.

Capacitor Features

The capacitor, as with other electronic components, is defined by a number of properties.These Capacitor Features can always be found in the data pages that the manufacturer provides us, so here we will share only a few of the more important ones.

Nominal Capacity ( C )

Nominal value of capacitance , C is onethe entire capacitorit is the most important of the capacitor properties.This value is measured in pico-Farads (pF), nano-Farads (nF) or micro-Farads (μF) andthe body of the capacitor is marked as numbers, letters or colored bands.

Acapacitance of the capacitor can change the value with ambient temperature and circuit frequency (Hz).Smaller ceramicsCapacitors can have a nominal value as low as a pica-Farad (1pF), while the nominal capacitance value of larger electrolytics can be as low as a Farad (1F).

Entirecapacitors have a tolerance rating that can vary from -20% to +80% to affect the actual or actual value of aluminum electrolytics.The choice of capacitance is determined by the circuit configuration, butthe value read next to the capacitor may not necessarily have a real value.

Operating Voltage, (WV)

Operating Voltage is an important capacitor feature. In general, the operating voltage printed on the side of a capacitor body corresponds to the DC operating voltage (WVDC).

DC and AC voltage values areit is usually not the same for the capacitor, since the AC voltage value refers to the value of rms and is NOT the maximum or peak value, which is 1,414 times larger.In addition, the specified DC operating voltage is normally valid in a certain temperature range, such as -30°C to +70°C.

Any DC voltage or excessive AC surge current that exceeds the operating voltage may cause failure.Therefore, it is concluded that a capacitor will have a longer working life if operated in a cold environment and within the rated voltage.The co-operation DC voltages are 10V, 16V, 25V, 35V, 50V, 63V, 100V, 160V, 250V, 400V and 1000V and are printed on the body of the capacitor.

Tolerance, ( ±% )

As with the resistances,capacitors are also generally less than 100pFhigher value in picofarad (±pF) for capacitors or usually higher than 100pFhas a Tolerance rating expressed as a plus or minus value in percentage (±%) for capacitors. .

The tolerance value is the measure that is allowed to differ from the nominal value of the actual capacitan and can vary from -20% to +80%.Therefore, a 100μF with a 20% tolerance to the ±The capacitor can generally range from 80μF to 120μF and can still remain within tolerance.

Capacitors are rated based on how close they are to their actual value compared to nominal capacitance with colored bands or letters used to indicate their true tolerance.The most common tolerance variation for capacitors is 5% or 10%, but some plastic capacitors are rated as low as 1% ±.

Leakage Current

Dielectric, which is used to separate conductive plates inside the capacitor, is not an excellent insulator, which causes a very small current to flow or "leak" from dielectric due to the effect of strong electric fields created by the load when applied to the plates.

To this small DC current flow in the nano-amperage (nA) regionit is called leakage current of capacitors.Leakage current is a result of electrons moving physically in a dielectric environment, at the edges or ends, and if the supply voltage is removed over timewill completely drain the capacitor.

Film or foil typeAs with capacitors, when the leakage is too low, it is often referred to as "insulation resistance" (R p) and can be expressed as a high-value resistance in parallel with the capacitor, as shown.When the leakage current is high, as in electrolytics, electrons are called "leakage current" because they flow directly through the electrolyte.

Capacitor leakage current is an important parameter in amplifier coupling circuits or power supply circuits, the best options for coupling and/or storage applications teflon and other plastictypes of capacitors (polypropylene, polystyrene, etc.). The lower the dielectric constant, the higher the insulation resistance.

Electrolytic type, on the other handcapacitors (tantalum and aluminum) can have very high capacitances, but they also have very high leakage currents (typically approximately 5-20 μA/μF) due to their weak insulation resistance and are therefore not suitable for storage or joining applications.In addition, the flow of leakage current for aluminum electrolytics increases with temperature.

Operating Temperature ( T )

Changes in temperature around the capacitor affect the value of capacitance due to changes in dielectric properties.If the air or ambient temperature overheats or cools,the capacitance value of the capacitor may vary enough to affect the correct operation of the circuit.Mostnormal operating range for capacitor, especially plasticFor capacitor types , +70 o is C with nominal voltage values given for a Operating Temperature of no more than C – 30 o C to +125 o C.

Electrolytic in generalAt high temperatures for capacitors and especially aluminum electrolytic capacitors, liquids in electrolytes above +85oC can evaporate and disappear, and the body of the capacitor can be deformed, especially due to small dimensions internal pressure. In addition, electrolytic capacitors cannot be used at low temperatures below -10 o C, as the electrolyte jelly freezes.

Temperature Coefficient ( TC )

The Temperature Coefficient is the most change in capacitance over a certain temperature range of the capacitor.OneThe temperature coefficient of the capacitor is usually expressed linearly as a millionth of a piece per degree Celsius (PPM/o C) or a percentage change in a certain temperature range. Somecapacitors are not linear (Class 2 capacitors) and increase their values as the temperature rises, giving them a temperature coefficient expressed as positive "P".

Somecapacitors reduce their value as the temperature increases and they are given a temperature coefficient expressed as negative "N".For example, "P100" +100 ppm/ o C or "N200", that is, -200 ppm/ o C, etc. However, somecapacitors do not change their values and remain constant in a certain temperature range, suchcapacitors have a value of zero. temperature coefficient or "NPO".This type, such as Mika or Polyestercapacitors are usually classified in Class 1capacitors.

Mostcapacitors lose capacitance, especially when electrolytics heat up, but temperature stabilizer capacitors are available in at least the range P1000 to N5000 (+1000 ppm/ o C to -5000 ppm/ o C).It is also possible to connect a capacitor with a positive temperature coefficient to a capacitor with a negative temperature coefficient in series or parallel, the net result is that the two opposite effects cancel each other out in a certain temperature range.Temperature coefficientAnother useful application of capacitors is to use them to eliminate the effect of temperature on other components within a circuit, such as inductors or resistors.

Polarization

Capacitor polarization, electrolytic type in generalit refers to capacitors, but mainly aluminum electrolytics in relation to their electrical connections.ElectrolyticSince capacitors must be at the correct polarity, the voltage connected to the capacitor terminals must be connected to positive to positive and negative poles to negative.

Incorrect polarization,it can cause the oxide layer inside the capacitor to deteriorate, causing very large currents to flow from the device and, as we mentioned earlier, deterioration.

ElectrolyticMost capacitors have negative, -and terminals clearly marked with a black strip, tape, arrows or angular double brackets on one side of their body, as shown, to avoid any incorrect connection to the DC resource.

Metal boxes or bodies of some larger electrolytics are connected to the negative terminal, but metal boxes of high-voltage types are instrained by electrodes brought to separate metal or screw terminals for safety.

In addition, when using aluminum electrolytics in power supply softening circuits, care should be taken to prevent the sum of the peak DC voltage and AC surge voltage from being "reverse voltage".

8. Equivalent Serial Resistance, (ESR)

When used at equivalent Serial Resistance or ESR high frequencies, the capacitor's AC impedance and dielectric material, a capacitor containing the resistance of the joining lines DC resistance, dielectric and dc resistance of the connectionsall capacitor plate resistance is measured at a certain frequency and temperature.

In some ways, ESR,it is the opposite of the insulation resistance, which is presented as a pure resistance (no capacitive or inductive reactance) in parallel with the capacitor.An idealthe capacitor will only have capacitance, but ESR,it is presented in series with the capacitor (therefore equivalent serial resistance name) and as a pure resistance (less than 0.1Ω), which depends on the frequency and makes it a "DYNAMIC" quantity.

Since ESR identifies energy losses of the "equivalent" serial resistance of a capacitor, especially when used in power and switching circuitscapacitor must determine total I2R heating losses.

Has a relatively high ESRCapacitors are capable of bringing current from their plates and plates to the external circuit due to longer charging and discharge RC time constant.ElectrolyticThe ESR of capacitors increases over time as their electrolytes dry out.Very low ESR valuescapacitors are available andthe capacitor is optimal when used as a filter.

As a final note, small capacitance (less than 0.01μF)capacitors usually do not pose much danger to humans.However, when their capacitance begins to exceed 0.1μF,touching the capacitor tips can be a shocking experience.

Capacitors are capable of storing an electrical charge in the form of voltage among themselves even when there is no circuit current, which gives them the ability to store a large electrolytic type reservoir located on television setscapacitors, photo flashes and potentially storingthe capacitor gives a kind of storage with banks.

As a general rule, once the power supply is removed,never touch the ends of capacitors.In such cases, you can discharge these capacitors and take any action you want.

Here are many available to define working conditionswe have listed only a few of the capacitor features, and in the next tutorial on capacitors,We will look at how capacitors store the electrical charge on their plates and calculate the capacitance.