NIPPON CHEMI-CON CORPORATION

When an aluminum electrolytic capacitor is charged and the terminals are short-circuited, then left open for a while, the voltage across the terminals spontaneously increases again. This voltage is called the “recovery voltage.” The mechanism for this phenomenon is believed to be as follows:

When a voltage is applied to a dielectric, electrical changes occur within the dielectric due to dielectric action, and the dielectric surface becomes charged with polarities opposite to the applied voltage. (Polarization effect)

This polarization effect occurs both rapidly and slowly. Therefore, when voltage is applied and then discharged until the terminal voltage reaches 0V, and the terminals are left open, the slowly polarizing component appears across the terminals as recovery voltage. (Fig.28)

【Fig.28】Mechanism of Recovery Voltage

The recovery voltage changes over time as shown in Fig.29, reaching its peak approximately 10 to 20 days after the terminals are opened, then gradually decreasing. Additionally, larger capacitors (screw terminal type and snap-in type) tend to produce higher recovery voltages.

【Fig.29】Change of Recovery Voltage

The recovery voltage value varies depending on manufacturing lot and product specifications, but generally tends to increase as the rated voltage of the product increases.
Please note that depending on product specifications, voltages of several tens of volts or higher may be generated.

【Fig.2】<Example> Time Variation of Capacitor Recovery Voltage (Radial Lead Type)

If the terminals are inadvertently short-circuited after recovery voltage has developed, sparks may occur, which can frighten workers on assembly lines or damage low-voltage components such as CPUs and memory devices in the circuit. To prevent this, discharge the accumulated charge through a 100 to 1kΩ resistor before use. Nippon Chemi-Con can also provide solutions for this issue. Please consult us.