An open failure also occurred if the internal wiring between the capacitor element and the external terminal is broken or significantly increased resistance at connections (the dashed red line in Figure 2). There are various/many specifications and connection methods of external terminals and internal wiring.
A low-impedance failure develops across the capacitor terminals or from a phase terminal to ground. A broken connector could cause such a fault. Most failures are progressive. Sudden jumps to high current are rare. To detect progressive failures quickly, fusing must be very sensitive.
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.
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.
In the case of film capacitors, when a local short circuit failure occurs, the shorted area may temporarily self-heal. An open mode failure in a capacitor can have undesirable effects on electronic equipment and components on the circuit.
Physical Damage: Mechanical stress, vibration, or impact can physically damage capacitors, leading to internal short circuits or breakage of the connections. Aging and Wear: Over time, capacitors naturally degrade. Electrolytic capacitors, in particular, can dry out, losing their ability to store charge effectively.