What is Aluminum Capacitors? 5 effects of low temperature

Aluminum capacitors are a type of electrolytic capacitor. A capacitor is a two terminal electrical component that can store energy, somewhat like a battery. Aluminum capacitors are polarised, meaning that the energy can only flow in a single direction. The aluminium forming an extremely thin insulating layer of aluminum oxide, which acts as the dielectric of the capacitor.

Low Temperature Characteristics of Aluminum Electrolytic Capacitors

Various parameters of aluminum electrolytic capacitors, as well as in operation temperatures and electrical ratings, are greatly influenced by the characteristics of the electrolyte. The properties of the liquid electrolyte that are considerably affected by temperature variations include electrical conductivity and viscosity. The electrical conductivity of the electrolyte increases with an increase in temperature and reduces with a decrease in temperature. Temperature variations have additional impact on the characteristics of aluminum electrolytic capacitors than on alternative kinds of capacitors. Some of the functional parameters for aluminum electrolytic capacitors that are considerably affected by changes in temperature include capacitance, equivalent series resistance (ESR), tangent delta, leakage current, and impedance.

Capacitance

Temperature changes have vital effects on the capacitance of AN aluminum electrolytic capacitor. As the temperature of the electrolyte decreases, its viscosity increases resulting in a reduced electrical conductivity. Therefore, the capacitance of metal electrolytic capacitors reduces with a decrease in temperature. At low frequencies, the relationship between temperature and capacitance of aluminum electrolytic capacitors is nearly linear. When in operation at -400C, low-voltage aluminum electrolytic capacitors with a low temperature rating of -550C exhibit a capacitance loss of between -10% and -20%. Capacitance loss for high-voltage capacitors can be up to 40%. When in operation at the low-temperature limit, the capacitance of aluminum electrolytic capacitors with a low temperature rating of -550C declines by less than 20%.

Equivalent Series Resistance (ESR)

The resistive component of an equivalent series circuit of a capacitor is referred to as the equivalent series resistance (ESR). The ESR of aluminum electrolytic capacitors is considerably affected by variations in temperature and frequency. In wet atomic number 13 electrolytic capacitors, drastic changes in capacitance are observed when temperature drops. The changes in capacitance are mainly due to the effect of temperature variation on the electrolyte, rather than on the dielectric. The resistivity of the electrolyte increases with a decrease in temperature. For instance, when the temperature drops from 250C to -550C, the resistivity of the electrolyte can increase by a factor of about 100, resulting in a considerable increase in ESR. In wet aluminum capacitors, dramatic changes in ESR are observed as the temperature decreases. For an aluminum electrolytic capacitor operating at the low-temperature limit, the ESR is more than 10 times. If a capacitor with a low-temperature rating of -200C is operated at -400C, its equivalent series resistance can increase by more than a factor of two.

Leakage Current

The leakage current of an electrolytic capacitor is primarily dependent on the characteristics of the dielectric material. Crystal defects, cracks, stress, and installation-related damages are some of the main causes of leakage current. Although the value of leakage current can be decreased by minimizing these defects, it cannot be fully eliminated. The key factors that affect leakage current include temperature, time, applied voltage, and the design of a capacitor. The leakage current increases with an increase in temperature and reduces with a decrease in temperature. For aluminum electrolytic capacitors, this useful parameter is typically stable at low temperatures. In addition, the initial run current of associate degree aluminum electrolytic capacitor depends on storage length and conditions.

Impedance

The impedance of AN Aluminum capacitor depends on frequency and temperature. It comprises capacitive reactance of the capacitor, ohmic and dielectric losses of the foils, electrolyte, and terminals, and inductive reactance of the capacitor windings. The capacitive reactance and the equivalent series resistance depend on both frequency and temperature, while inductive reactance depends on frequency only. The impedance of AN aluminum electrolytic capacitor will increase with a decrease in temperature. When an aluminum electrolytic capacitor is working at its low-temperature limit, it impedance increases by up to 10 times.

Dissipation Factor 

Dissipation factor or tangent of loss angle of a capacitor refers to the ratio of equivalent series resistance to capacitive reactance. The dissipation issue of an aluminum electrolytic capacitor depends on each temperature and frequency. This parameter increases with a decrease in temperature.