1.2.2.2 Dielectric loss

A physical process in which a dielectric converts a portion of electrical energy into thermal energy under the action of an electric field is known as dielectric loss. The magnitude of the dielectric loss is related to the applied electric field frequency, electric field strength, fiber constant, and dielectric loss angle. In unit time, the heat energy P produced per unit volume of fiber is

$$P = 0.556f \cdot E^2 \cdot e\_r \cdot \tan \delta \cdot 10^{-12} \tag{4}$$

where P is the power consumed by the electric field (W/cm<sup>3</sup> ); f is the frequency of the applied electric field (Hz); E is the external electric field strength (V/cm); and tan δ is the tangent of the dielectric loss angle δ.

The dielectric constant of dry textile material generally is 2–5, for which tan δ is equal to 0.02–0.05. The dielectric constant of water is 20–80, for which tan δ is 0.15–1.2. Therefore, the higher the moisture content of the textile material, the larger than tan δ.
