Dielectric loss

Description

Of the loss angle is defined as the arc tangent of the ratio of real power to reactive power. To distinguish this is the cosine of the angle of the phase shift φ as the ratio of real power to apparent power.

The smaller the loss angle, the closer the real components are an ideal behavior. An ideal inductor has a loss angle of 0 °. An ideal capacitor also has a loss angle of 0 °.

The other hand, is an ideal electrical resistor has a loss angle of 90 °; it has no capacitive or inductive reactive components.

The loss angle can be calculated on the complex impedance Z or the phase shift between current and voltage of the device:

Loss factor of a coil:

Dissipation factor of a capacitor:

R the equivalent series resistance in the equivalent circuit diagram of the component

The equivalent series resistance (. Shortly ESR, of Engl Equivalent Series Resistance ) represents the equivalent circuit diagram all losses:

• The ohmic losses in the cables and winding wires
• In addition coils, eddy current, skin effect, proximity effect and core losses ( hysteresis )
• In addition, the dielectric loss factor of the capacitors, and the insulation resistance

Since change in the real component of the impedance real and imaginary parts, and so that the phase shift varies greatly with frequency, usually changes also the loss tangent at the frequency; he eats normally with this.

The smaller is the equivalent series resistance in series equivalent circuit of a capacitor, the smaller the loss tangent. Accordingly, even when a small coil with a small loss angle ESR in series equivalent circuit.

The loss angle is one of its important characteristics especially in capacitors next to the capacitance value; it is determined at a particular frequency, which depends on the purpose of the capacitor and is specified in the data sheet.

Note: All previous paragraphs apply for equal frequency sinusoidal voltages and currents.