Ping Shang explains the knowledge of aluminum electrolytic capacitors
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Understanding Aluminum Electrolytic Capacitors
The capacitance of electrolytic capacitors is influenced by the impedance they exhibit when subjected to alternating current (AC) voltage. As a result, the measured capacitance value—often referred to as the AC capacitance—can vary depending on the operating frequency, applied voltage, and the measurement technique used. According to the standard JISC 5102, the capacitance of aluminum electrolytic capacitors is typically measured at a frequency of 120 Hz, with a maximum AC voltage of 0.5 Vrms and a DC bias voltage ranging from 1.5 to 2.0 V. It is well established that the capacitance of these components tends to decrease as the frequency increases.
In the equivalent circuit model of a capacitor, the ratio of the series equivalent resistance (ESR) to the capacitive reactance (1/ωC) is known as the dissipation factor, or tan δ. The ESR value is usually measured at 120 Hz. As the measurement frequency rises, tan δ increases, and it also tends to rise when the temperature decreases. This behavior is important in applications where performance under varying conditions must be considered.
Impedance (Z) represents the opposition that a capacitor offers to the flow of alternating current at a specific frequency. It is closely related to both the capacitance and inductance values within the capacitor’s equivalent circuit, as well as the ESR. At higher frequencies, the inductive component becomes more significant, which affects the overall impedance characteristics of the device.
Understanding these parameters is essential for selecting the right electrolytic capacitor for a given application, especially in power supply circuits, audio systems, and other electronic designs where stability and performance are critical. By considering factors like frequency, temperature, and voltage, engineers can ensure optimal operation and longevity of their electronic components.
By: Hardware Business Network Information Center
Source: http://news.chinawj.com.cn