What are the abnormal characteristics of capacitors

What type of capacitor is most likely to fail?

Mica and tantalum capacitors are more likely to fail in the early period of use (early failure), while aluminum electrolytic capacitors are more likely to experience wear-out failure due to aging use. In the case of film capacitors, when a local short circuit failure occurs, the shorted area may temporarily self-heal.

What happens if a capacitor fails a short circuit?

When a capacitor fails a short circuit (Figure 3), DC current flows through the capacitor and the shorted capacitor behaves like a resistor. For example, if a capacitor, placed between the input line and ground to remove AC current such as ripple current or noise, is shorted, DC current directly flows from the input to ground.

Why do paper and plastic film capacitors fail?

Paper and plastic film capacitors are subject to two classic failure modes: opens or shorts. Included in these categories are intermittent opens, shorts or high resistance shorts. In addition to these failures, capacitors may fail due to capacitance drift, instability with temperature, high dissipation factor or low insulation resistance.

What happens if a capacitor fails?

When current repeatedly flows into a defective part due to overvoltage or dielectric degradation, the capacitor continues to self-heal and loses capacitance. Generally, a capacitor is considered to have failed when its capacitance drops by 3% or more compared to its initial value. The probability that a failure will occur is called 'failure rate'.

What are the characteristics of a capacitor?

The most basic characteristic of a capacitor is capacitance (C), but it has many other characteristics such as equivalent series resistance (ESR), dielectric loss tangent (tanδ), insulation resistance, leakage current, withstand voltage, equivalent series inductance (ESL) and impedance.

How to prevent a capacitor failure?

Such failures can be avoided with preventive maintenance action such as replacing the capacitor. For film capacitors, the typical failure mode is capacitance decrease due to self-healing, so it is possible to diagnose the life expectancy by understanding the capacitance change.