Dissipation factor alternating currents

Material response is typically studied using either direct (constant) applied voltage (DC) or alternating applied voltage (AC). The AC response as a function of frequency is characteristic of a material. In the future, such electric spectra may be used as a product identification tool, much like IR spectroscopy. Factors such as current strength, duration of measurement, specimen shape, temperature, and applied pressure affect the electric responses of materials. The response may be delayed because of a number of factors including the interaction between polymer chains, the presence within the chain of specific molecular groupings, and effects related to interactions in the specific atoms themselves. A number of properties, such as relaxation time, power loss, dissipation factor, and power factor are measures of this lag. The movement of dipoles (related to the dipole polarization (P) within a polymer can be divided into two types an orientation polarization (P ) and a dislocation or induced polarization. 

Alternating currents generally are displaced in time such that it is out of phase with the voltage by an angle 5. The tangent of this angle is the dissipation factor and is related to the power loss as follows ... 

The ratio of the power loss to the power output is called the dissipation factor, tan 8. The power loss is zero when the current and voltage are in phase but increases when the phase difference between the alternating potential and the amplitude of the current is 90°. 

Of more importance is the loss factor, tan 8, denoting the fraction of the transmitted alternating current lost by dissipation in the material. Here large differences occur between polymers, as indicated in Figure 8.10. It appears that polymers with the highest specific resistance also show the lowest dielectric losses. It should be remarked, that the values given are very schematical the losses are strongly dependent on frequency and temperature. 

The loss is converted to heat (dissipation). For low values of 6, the losses are low so that in the limit 6 = 0, there is no loss (this is the ideal capacitor). Low values of tan 6 may be approximated as tan 6 sin 6 cos 6, where cos 6 is defined as the power factor, 6 represents the angle between the direction of the voltage and current in an alternating current. Then Power = Voltage X Current x Power Factor. The loss factor approximately equals the product of the power factor and the dielectric constant, all values taken at a frequency of 60 Hertz. In nonpolar polymers (Teflon, polyolefins, polystyrene)... 

The electrical properties of a number of the polyoximes was studied. All of the structures studied can offer what is referred to as whole-chain resonance — that is, the polymer backbone consists entirely of alternating double bonds with the exception of the metal atom. Values for the dissipation factor D ranged from 3 to 10 (at 10 Hz) the bulk resistivity P, from 0.05 to 0.6 (at 10 Hz), and the bulk capacitance from 0.2 to 0.9 K. Thus most of the materials are semiconductors. Efforts are currently imder way to evaluate some of these after doping. 

Alternating eurrent loss and permittivity Electrieal insulation Direet eurrent electrical resistance High voltage, low current arc resistance Dieleetric constant and dissipation factor Corona discharge... 

As all electrical insulating materials, EP-resins exhibit low electrical conductivity which results in current loss in operation. Thermal losses from current load in an encapsulated conductor or device and the dielectric dissipation loss generated in the EP-resin-molding material result in temperature increases that lower electrical con-ductibility and dielectric strength [885], because in principle, all mechanisms participating in DC current transport and displacement processes also cause dielectric losses in the alternating field. The dielectric behavior of insulating materials is described by the temperature-, frequency-, and stress-dependent (i.e. field intensity dependent) loss factor tan 6 and the dielectric constant s. 

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