Dielectric Loss

What is Dielectric?

A material with a poor electrical conductivity that receives the ability to store an electrical charge because of dielectric polarization is referred to as dielectric. Hence, showing only displacement current makes it perfect for constructing a capacitor; to store and return electrical energy. To understand the topic better, you must know the dielectric loss definition and other related concepts. 

What is Dielectric Loss?

The loss of energy involved in heating a dielectric material in an assorted electric domain is called dielectric loss. For instance, a capacitor assimilated in an alternating-current circuit is barely charged and discharged each half cycle. Most importantly, dielectric losses generally are based on the frequency and the dielectric material. 

Dielectric loss is measured utilizing what is referred to as the loss tangent or tan delta (tan δ). In layman’s language, tan delta is the tangent of the angle between the alternating field vector and the material’s loss component. So, the higher the value of tan δ the significant the dielectric loss should be.

Heating through dielectric losses is considerably used in industries for drying lumber and various other fibrous materials, heating thermosetting glues, fast jelling and drying foam rubber, and preheating plastics prior to molding. Dielectric constant and loss tangent are numerical values that help define the permittivity of a dielectric material. The permittivity of dielectric material is indicated by ‘ε’.

The dielectric constant formula is K = \[\frac{E_{0}}{E}\] , or the ratio of the electric field in a vacuum to that in the dielectric material, and is considerably connected to the polarizability of the material.

Causes of Dielectric Loss

A coherent dielectric supports a varied charge with the least possible dissipation of energy in the form of heat. There are normally two major forms of loss that may dissipate energy inside a dielectric. During conduction loss, a flow of charge through material results in energy dissipation. The dielectric loss tangent is the dissipation of energy through the movement charges in a substituting electromagnetic field as polarisation switches direction. 

Moreover, dielectric losses are particularly high around the relaxation or resonance frequencies of polarisation mechanisms. The polarization delays the applied field, resulting in an interaction between the field and the dielectric’s polarization, leading to heating.

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A dielectric loss is prone to be higher in materials with higher dielectric constants. It is the prominent drawback of employing these materials in practical applications. 

For example, dielectric loss is used to heat food in a microwave oven. The frequency of a microwave utilized is nearly the same as the relaxation frequency of the orientational polarisation mechanism in the water. It means that any water present soaks up extensive energy that is then dissipated in the form of heat. Moreover, the exact frequency utilized is a little away from the frequency at which maximum dielectric loss happens in water to ensure that the microwave is not all engrossed by the first layer of water they confront; thus letting proper heating of the food.

Factors Affecting Dielectric Loss

The dielectric losses and d.c conductivity of insulating oils reduce with time after the oil is added to the test cell, excluding the electric stress and room temperature. When the cell is heated instantly after filling, the loss tangent and d.c conductivity upsurge to a maximum, but then reduces to a much lower value with time at persistent temperature. The maximum value, the rate of increase to that value and the subsequent reduction with time are basic functions of the thermal capacity and shape of the cell. It is the method employed to clean the cell, the temperature and the oxygen element of the oil. 

The following drop-in dielectric loss is considered because of the catalytic oxidation of most elements in the oil at the metal-electrode surface, even though it’s attainable that ions may simply be confined at this surface. The effects are detected with a low-viscosity cable infusion, both unused and widely contaminated, transformer oil and a synthetic hydrocarbon. 

Moreover, the imputations of the effect are examined in reference to regular testing of oils, to an analysis of the contamination effects in oils and to work on oil-infused paper. It’s possible that the utilization of plastic-coated electrodes may partially or entirely remove the effect.

What is Loss Tangent?

Loss tangent (tan (δ)) estimates signal loss because of the fundamental dissipation of electromagnetic energy in the substrate of the printed circuit board. Moreover, it is a dimensionless quantity and mostly considered as; Loss Factor, Tan δ, Dissipation factor and Loss angle. The loss tangent definition is then referred to as the ratio or angle in a complex plane of the lossy reaction to the electric field in the curl equation to lossless reaction. 

The Formula for Loss Tangent is:

D = tanδ = cotθ = \[\frac{1}{2πR_{p}C_{P}}\]

Where; δ is the loss angle, θ is the phase angle, f is the frequency, Rp is equivalent parallel resistance, and Cp is equivalent parallel capacitance. Loss tangent has a vital part in extremely high frequencies above 1 GHz and analog signals to decide the signal attenuation.

FAQs (Frequently Asked Questions)

Q.1 Explain how Dielectric Loss depends on Frequency?

Ans. Usually, a dielectric loss reduces with surging frequency. The dielectric properties of a polymer are decided by the charge distribution and also by the statistical thermal motion of its polar group. Moreover, the polarization of dielectric is supplied by electronic, ionic, and dipole polarization. 

Q.2 Is Water Considered a Dielectric?

Ans. Pure water is known to be a nonpolar dielectric. However, they are not at rest and can’t be persuaded to generate an electric field such as a solid dielectric. The motion of water molecules differs the volume of a capacitance continuously. Thus, water can’t be considered as a dielectric in a capacitor.  

Q.3 How does a Dielectric Work? 

Ans. Initiating a dielectric into a capacitor reduces the electric field, further decreasing the voltage and increasing the capacitance. A capacitor with a dielectric reserves the same charge as one without a dielectric, but at a minimum voltage. Moreover, capacitance and voltage are contrarily proportional when a charge is persistent. 

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