CONDENSADOR

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WHAT IS A CONDENSER?

The condenser or capacitor is a passive component which is capable of storing energy in the form of an electric field. This field is the result of a separation of the electric charge. It is formed by a pair of conductive surfaces, generally of sheets or plates which are separated by a dielectric material or by vacuum. The plates subjected to a potential differential acquire a certain electric charge (positive in one of them and negative in the other), the total charge variation being zero. A capacitor is a two-terminal device and may have polarity at its terminals.

The dielectric material is an insulator that increases the capacitance as a result of permanent or induced electrical dipoles in the material. Strictly speaking, the direct current (DC) does not flow through a capacitor, instead the charges move from one side of the capacitor through the conductor circuit to the other side, which establishes the electric field. The displacement of the charge is called the displacement current because the current seems to flow momentarily through the device.

The voltage-current ratio of the capacitor is defined as:

formula01.png

Where q (t) is the amount of cumulative charge measured in coulombs and C is the capacitance measured in farads (F = coulombs / volts). To differentiate this equation, you can relate this displacement current to the voltage change rate:

I(t)= C
dV / dt

The capacitance is a property of the dielectric material and the geometry and separation of the plates. Typical capacitor values vary from 1 pF to 1000 uF. Since the voltage across a capacitor is the integral of the displacement current, the voltage can not change instantaneously. This feature can be used for timing purposes in electrical circuits as a simple RC circuit.

In experimental matters, the capacitor is capable of storing the electrical energy it receives during the charging period, the same energy that it yields later during the discharge period.

SIMBOLOGY

The shape of a capacitor is rectangular, square, circular, cylindrical or spherical. As different types of capacitors are available, there are different symbols available to represent them that are shown below.

 
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Types of capacitors

The main types of commercial capacitors are electrolytic capacitors, tantalum capacitors, ceramic disc capacitors and mylar capacitors. The electrolytic capacitors are polarized, which means that they have a positive and a negative end. The positive side of a polarized capacitor must be maintained at a higher voltage than the negative side; otherwise, the mechanism will usually be damaged.

 
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WHY ARE CONDENSERS IMPORTANT?

The condensers have many properties like

  1. It can store the energy and can dissipate this energy to the circuit when necessary.

  2. It can block DC and allow AC to flow through it, and this can couple one part of the circuit with the other.

  3. Circuits with condensers depend on the frequency, so they can be used to amplify certain frequencies.

  4. Allow high frequencies and can be used as filters to filter casualties or to collect high ones.

  5. Since the reactance and capacitor frequency are inversely related, this can be used to increase or decrease the impedance of the circuit to a certain frequency and can be used as a filter.

Likewise, condensers exhibit many properties when used in AC or DC circuits and, therefore, play an important role in electrical and electronic circuits.

DIELECTRIC OF A CONDENSER

The dielectric act as an insulating material between the plates. The dielectric can be any non-conductive material such as ceramic, waxed paper, mica, plastic or some form of liquid gel.

The dielectric also plays an important role in deciding the value of the capacitance. As the dielectric is introduced between the plates of the capacitor, its value increases.

The different dielectric materials will have different dielectric constants, however, this value is >1.

The following table shows the value of the dielectric constant for each dielectric material.

Dielectric can be of two types

  1. Polar dielectrics: these dielectrics will have permanent dielectric movement

  2. Non-polar dielectrics: These will have a temporary dielectric moment. By placing them in an electric field, they can be induced with dipole moments.

VOLTAGE CLASSIFICATION OF A CONDENSER

This is not voltage until the capacitor is charged but the maximum voltage to which the capacitor can operate safely. This voltage is called working voltage (WV) or DC working voltage (DC-WV).

If the capacitor is applied with a voltage greater than this voltage, it can be damaged by producing an arc between the plates due to the dielectric breakdown.

When designing circuits with condensers, care must be taken that the capacitance of the capacitor is greater than the voltage used in the circuit. For example; if the operating voltage of the circuit is 12 V, then it is necessary to choose a condenser with a nominal voltage of 12 V or higher.

This working voltage of a condenser depends on factors such as the dielectric material used between the capacitor plates, the dielectric thickness and also the type of circuit used. 

GENERAL TECHNICAL CHARACTERISTICS

  • Rated capacity:

It is the theoretical value expected at the end of the manufacturing process. It is marked on the body of the component by means of a color code or directly with its numerical value.

  • Tolerance:

Difference between deviations capacity, higher or lower depending on the manufacturer.

  • Nominal voltage:

It is the voltage that the capacitor can support in a continuous way without suffering deterioration.