The influence of environment on the performance of capacitors

The factors that affect the performance and life of capacitors are: ambient temperature, humidity, vibration, shock and other reasons. Let's talk about the impact of capacitors on performance in various environments.

   High temperature: The temperature of the working environment around the capacitor is very important. The rise in temperature accelerates the chemical reaction, the medium material is easy to age, and the service life decreases with the increase of temperature. The increase in capacitance with temperature depends on the relationship between the dielectric constant of the medium and the temperature. With the increase of the positive temperature coefficient, the capacity becomes larger, and the capacity with a negative temperature coefficient decreases with the increase of temperature. Therefore, the operating voltage must be lowered when the upper limit of use temperature is increased. The high temperature oxidizes the metal, increases the contact resistance, the resistance increases and the loss increases.

  Low temperature: It makes the material brittle, the epoxy resin cracks and loses its protective effect. Moisture penetrates into the capacitor and its performance decreases.

  High and low temperature impact: Alternate condensation, freezing and evaporation will occur, causing the encapsulation layer to crack, and the cracking will cause water vapor to penetrate and accelerate the deterioration of the capacitor's performance.

   High humidity: Water vapor condenses and absorbs on the surface of the capacitor, which reduces the insulation resistance of the capacitor, causing leakage and arcing. As the dielectric constant increases, the dielectric loss increases. Water vapor entering the metallized layer of the capacitor will be corroded, which will reduce the capacity and increase the loss.

   Alternate heat and humidity: The water vapor absorbs and diffuses after being absorbed on the surface of the capacitor. The effects of respiration and heating condensation can accelerate the penetration of water vapor into the capacitor, making the performance of the capacitor deteriorate as described above. In the case of the same relative humidity, when the temperature rises, the number of water molecules increases and the formation of molecular gaps is accelerated. Water molecules can enter these gaps from the surrounding air and penetrate into the interior of the medium. In the case of the same absolute humidity, the lower the temperature, the higher the relative humidity, and the more moisture the capacitor can absorb.

   Dynamic environment: Vibration, shock and acceleration will damage the capacitor, and small changes in the structure will cause the capacitance to change. There will also be phenomena such as wire breakage and poor contact.

   Low air pressure environment: In a high-altitude environment, as the altitude increases, the air pressure decreases, and the electrical resistance of the air decreases. Arcing and corona will occur, and the compressive strength will decrease. When the air is thin, it will be more difficult to dissipate heat.