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 Capacitor Characteristic Parameters

• 1. Nominal Capacity and Tolerance

  The nominal capacitance is the value marked on the capacitor. The standard unit is Farad (F), but it's rarely used in practice due to its large size. Common conversions include: 1F = 1000mF, 1mF = 1000μF, 1μF = 1000nF, and 1nF = 1000pF.

  The deviation between actual and nominal capacitance is called the tolerance. For example, Class I capacitors have ±5% tolerance, while electrolytic capacitors may have wider tolerances like ±20% or more depending on application.

  2. Rated Voltage

  This is the maximum DC voltage that can be continuously applied without causing damage. Exceeding this value can lead to breakdown and permanent failure. It is usually marked directly on the capacitor body.

  3. Insulation Resistance

  It refers to the resistance between the capacitor plates when a DC voltage is applied. A higher insulation resistance indicates better performance, especially for larger capacitors where internal dielectric quality matters most.

  4. Loss (Dissipation Factor)

  Loss occurs due to energy dissipation as heat. This includes dielectric loss, conduction loss, and resistance from metal parts. In AC conditions, polarization effects also contribute to losses.

  5. Frequency Characteristics

  As frequency increases, the effective capacitance of general capacitors tends to decrease, which affects their performance at high frequencies.

  Operating Voltage of Electrolytic Capacitors

  Common voltages include 6.3V, 10V, 16V, 25V, 35V, 50V, 63V, 80V, 100V, 160V, 200V, 300V, and 400V. They operate within a temperature range of -40°C to +105°C (for lower voltages) and -40°C to +85°C (for higher voltages). These capacitors are polarized and used mainly for filtering and rectification in DC circuits.

  Screening Method for Electrolytic Capacitors

  Electrolytic capacitors are known for quality variability. A reliable screening method involves testing under extreme working voltages and high temperatures. This helps identify weak units that might fail during operation. A custom-built test fixture with a voltmeter, bulb, and switch can be used to simulate real-world conditions and detect faulty components.

  Determining Polarity and Quality Inspection

  Electrolytic capacitors are polarized and must not be reversed. To determine polarity, you can check the physical markings or use a multimeter. For unmarked capacitors, the longer lead is typically positive. Measuring leakage resistance and checking for capacitance using a multimeter can help assess quality. A good capacitor will show a clear deflection of the meter needle, indicating proper charging and minimal leakage.