In this theory, effect of temperature,
voltage and current on the life of capacitor is given. The life of capacitor is
affected by

# Factors affecting life of capacitor

## Effect of Temperature on life of capacitor

The temperature depends upon following parameters.

*Ambient temperature at which capacitor is operated*

*Over current flows through capacitor*

*Dielectric and resistive power loss in the capacitor*

- As the temperature increases, there is fast degradation of the dielectric.
- The life of capacitor is reduced to half for every 10 degree increases in the temperature.
- The life of capacitor reduces for faster degradation of the dielectric.
- There is expansion of impregnation and dielectric material if the temperature increases beyond its limit.
- The capacitor may be burnt in the worst condition.
- The classification of capacitor is done according to ambient maximum temperature operating condition.

Symbol |
Maximum ambient temperature |

A |
40 |

B |
45 |

C |
50 |

D |
55 |

## Effect of voltage on life of capacitor

- If the voltage increases beyond its specific limit, the dielectric of capacitor may breakdown.
- This will result in capacitor may short circuit permanently.

### Voltage limit for capacitor

+ 10% |
8 hours in 24 hours |

+15% |
30 min in 24 hours |

+20% |
5 min in 24 hours |

+30% |
1 min in 24 hours |

## Current flow through capacitor

### Over load current

- The over load current of capacitor is due to over voltage and harmonics.
- This may lead to local hot spot and internal short circuit of the capacitor.

### Inrush current

- When capacitor is switched on, a very high inrush current flows which may be 100 times rated current of capacitor.
- If the inrush current is not limited during frequent switching operation, it may lead to life of capacitor.

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