Loss factor tangent

Using this expression and taking into account the approach adopted, it is possible to experimental data on changes in the mechanical loss factor (tangent of mechanical losses) overtime, the impact loads to find the estimates of the activation energy of relaxation process, determine the extent to which the process is stationary (steady), the degree of linearity of the... 

Table 11.5 Highest permissible values of loss tangent or dielectric loss factor at rated voltages not exceeding 11 kV...

The heating characteristics of a particular material (for example, a solvent) under microwave irradiation conditions are dependent on the dielectric properties of the material. The ability of a specific substance to convert electromagnetic energy into heat at a given frequency and temperature is determined by the so-called loss tangent, tan <5. The loss factor is expressed as the quotient tan (3 = "/ , where e" is the dielectric loss, indicative of the efficiency with which electromagnetic radiation is... 

The loss tangent is an important quantity. The product of the loss tangent and the dielectric constant, tan 5, is called the loss factor and is the primary criterion for judging the usefulness of a dielectric as an insulator material. For this purpose, it is desirable to have a low dielectric constant and a small loss angle. For applications in which it is desirable to obtain a high capacitance in the smallest physical space, a high dielectric constant must be used, and a low value of the loss angle is needed. 

Figure 1.3 Dielectric spectra for range of alcohols in the frequency range of 107-10n Hz. The absolute permittivities at low frequencies fall as the size of the alcohol increases and they began to respond to the microwave fields at lower frequencies because their relaxation times become longer. The loss factors that control the efficiency of conversion of microwave into thermal energies also reach their maxima at lower frequencies. The loss tangent is the ratio of the loss factor and permittivity at that frequency. (Idealised from the raw data illustrated in Ref. 10.)...

Fig. 23 a, b. Dielectric properties of polyelectrolyte complexes881 (a) Variation of dielectric constant e and loss factor e" of polyelectrolyte complexes with frequency (b) Variation of loss tangent e"/e of polyelectrolyte complexes with frequency. NaSS = poly(sodium styrenesulfonate), PAA = polyfacrylic add), PVBMA = poly(4-vinylbenzyl-trimethylammonium chloride), PEI = polyethyleneimine, lonene (Bubond 60) = — 2CTK... 

Fig. 23, the polyeleetrolyte complexes exhibit relatively low dielectric constants (e ) and loss factors (c") which slowly decrease with increasing frequency except for the PAA-polyethyleneimine (PEI) system. Hence, the loss tangent (e"/c ) monotonously decreases with frequency. Moreover, even if polyelectrolyte complexes contain a certain amount of microsalt, is the direct current conductance low. This dielectric behavior has been ascribed to the polarizability of the electrolyte sorbed into isolated microscopic domains within the matrix of the polyelectrolyte complexes. 

Power factor. As used in dielectric measurements, the cosine of the angle whose tangent is the ratio of loss factor to dielectric constant, and hence a measure of both stored and dissipated energy within the dielectric medium. 

The loss tangent can be derived from material s eomplex permittivity. The real component of the permittivity is called the dielectrie eonstant whilst the imaginary component is referred to as the loss factor. The ratio of the loss faetor to the dielectric constant is the loss tangent. The complex dielectric constant is given by ... 

Fig. 5. Calculated structural loss factor based on RKU model for three-layer composite with varying Young s storage modulus and loss tangent of viscoelastic layer.

Dielectric loss factor The product of the dielectric constant and the tangent of the dielectric-loss angle for a material. 

The extent to which a material is heated when subjected to microwave radiation depends on two parameters the dielectric constant e and the dielectric loss factor e". The dielectric constant describes the ease with which a material is polarized by an electric field, while fhe loss factor measures fhe efficiency wifh which the electromagnetic radiation is converted into heat. The ratio of these properties gives the dielectric loss tangent or dissipation factor ... 

The dielectric permittivity of a medium (relative to the permittivity of free space, 8q = 8.85 X 10 F/m) is given by e and measures the polarization of the medium per unit applied electric field. The dielectric loss factor arises from energy loss during time-dependent polarization and bulk conduction. The loss factor is written as a". The loss tangent or dissipation of the medium, tan<5 is defined by e"/e. The orientation of molecular dipoles has a characteristic time r. Typically is short early in the cure but grows large at the end of the cure. 

Example What is the DM noise spectrum measured at the LISN for a 5 V 15 A flyback at an input of265 VAC, with a transformer turns ratio of 20 We are using an aluminum electrolytic bulk capacitor whose datasheet states that it has a capacitance of270 p,F, a dissipation factor (tangent of loss angle) of tan S = 0.15 as measured at 120 Hz, and a frequency multiplier factor of 1.5 at 100 kHz. 

A convenient way to evaluate the ability of two closely related substances to convert microwave energy into heat is to compare their respective loss tangent values, where the loss tangent is defined as the tangent of the ratio of the loss factor and the dielectric properties (Equation 25.1 Table 25.3). For deeper insight into the mechanism of microwave dielectric heating, the review by Mingos et al. is recommended. 

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