This article explains capacitor losses (ESR, Impedance IMP, Dissipation Factor DF/ tanδ, Quality FactorQ) as the other basic key parameter of capacitors apart of capacitance, insulation resistance and DCL leakage current.
There are two types of losses:
- Resistive real losses – these are real losses caused by resistance of leads, electrodes, connections etc. During current flow these losses are dissipated by Joule heat. Usually (unless it is intended by designed) the effort is to minimize these losses for maximum efficiency and high power load ratings.
- Reactance imagine losses – these are losses caused by capacitive reactance and inductive reactance “stored” in the component that can be reverted back
Figure 9. illustrates the behavior of different dielectric dipoles when they are affected by an alternating field. They will oscillate at the same frequency as the field’s if allowed by their reaction time. Every rotary motion requires energy and the executed work produces heat. The most inert dipoles will react to the very low frequencies and will here contribute to the losses. But as the frequency increases the different types of dipoles will not be able to respond quickly enough, one after another, as shown in the figure.
Just in the range where the reaction time of the dipoles and the frequency period coincide a kind of resonance occurs which causes the dipole types to react with a loss peak (Figure 9).
Observe that Figure 9. deals with dipole losses, nothing else. There are other dielectric materials which have no molecular dipoles. They are called non-polar while the others are called polar. This has nothing to do with the polarity dependence of electrolytics.
The sum of losses in a polar and a non-polar capacitor may look like the ones in Figure 10.
We shall remember that dielectric losses (material permittivity) may be frequency dependent and as per the basic capacitance calculation it is the only parameter responsible for capacitor frequency dependence in ideal capacitor (considering surface area of electrodes and thickness of dielectric stable). The real capacitor may have additional RLC ladder structure that limits its resonance and maximum operating frequency.