Electrolytic capacitor inspection method - Solutions - Huaqiang Electronic Network

Probe current voltage pin 420*4450 head diameter 5.0 over current current and voltage pin

SMD aluminum electrolytic capacitor

Brand AVX TPSE226M035R0125 Low impedance tantalum capacitor AVX 22

Photocoupler

Electrolytic capacitors are essential components in electronic circuits, especially for filtering and energy storage. Understanding their characteristics is crucial for proper application and selection.

• 1. Nominal Capacity and Tolerance

  The nominal capacitance is the value marked on the capacitor. Common units include microfarads (μF), nanofarads (nF), and picofarads (pF). The tolerance indicates the allowable deviation from the nominal value. For example, a capacitor with a 5% tolerance can vary by ±5% from its rated capacity. Electrolytic capacitors typically have wider tolerances, such as ±20%, while ceramic or film capacitors often have tighter tolerances like ±5% or ±1%.

• 2. Rated Voltage

  The rated voltage is the maximum DC voltage that the capacitor can safely handle without breaking down. Exceeding this voltage may cause permanent damage. It’s important to choose a capacitor with a voltage rating higher than the expected operating voltage, usually around 1.5 times the required voltage for safety.

• 3. Insulation Resistance and Leakage Current

  Insulation resistance refers to the resistance between the capacitor's plates when a DC voltage is applied. A higher insulation resistance means less leakage current. For capacitors larger than 0.1 μF, the insulation resistance is mainly determined by the dielectric material. The time constant (τ = R × C) is used to evaluate how quickly a capacitor discharges its stored charge.

• 4. Loss and Dissipation Factor

  Capacitor loss refers to the energy dissipated as heat due to internal resistance and dielectric effects. The dissipation factor (DF) is a measure of this loss. In AC applications, the loss increases with frequency due to polarization and conduction losses. In DC, the main loss is due to leakage current.

• 5. Frequency Characteristics

  As frequency increases, the effective capacitance of a general capacitor decreases due to the rise in reactance. This is why high-frequency circuits often use smaller capacitors with lower parasitic effects.

Electrolytic Capacitor Operating Voltage

Electrolytic capacitors operate at voltages ranging from 6.3V to 400V, with typical operating temperatures between -40°C and +105°C. They are known for large capacitance values but also for their polarity requirement. They are commonly used in power supply filtering and rectification circuits. Aluminum and tantalum electrolytics are the most common types.

Screening Methods for Electrolytic Capacitors

Quality screening is critical for ensuring reliable performance. One effective method involves charging and discharging the capacitor under its rated or slightly higher voltage, simulating real-world stress. If the capacitor fails during this process, it is considered defective. High-temperature testing can further reveal hidden issues.

Determining Polarity and Quality Inspection

Electrolytic capacitors are polarized, so identifying the positive and negative terminals is essential. Visual inspection (e.g., longer lead for positive) and multimeter tests (measuring leakage resistance) are common methods. A multimeter set to R×1k can help determine polarity by comparing forward and reverse resistance. A good capacitor will show a high resistance in one direction and a low resistance in the other.

In addition to polarity checks, measuring capacitance and leakage current helps assess the quality of the component. A capacitor with a shorted or open circuit will not function properly. Regular testing ensures long-term reliability in electronic systems.