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Page 319

| Dielectric absorption. When capacitors are disconnected from the supply, they remain generally in a charged state. Considerable energy is stored in a capacitor in this condition, and there is a voltage present between its terminals. This phenomenon is called dielectric absorption. If the capacitor were left in this charged state, anyone in contact with equipment might receive a dangerous shock, or the equipment itself might be damaged by an accidental short circuit. Capacitors, therefore, are provided with means of draining the stored energy. The discharge equipment may consist of resistors or inductive coils (reactors) permanently connected to the terminals of the capacitor bank. If the capacitors are connected directly to other equipment without the interposition of switches or over-current devices, however, no discharge equipment is required, since the charges will drain off rapidly through the windings of the equipment. |

| Safety interlocks. To prevent exposure to energized or charged capacitor banks, interlocks are sometimes provided for the vaults or enclosures in which the banks are installed. These interlocks may be mechanical, requiring the associated breaker or switch to be opened and some time delay introduced before access to the capacitors can be obtained. Other systems provide electrical interlocks to accomplish the same purpose. |

| Maintenance |

| Very little maintenance is required for capacitors. Regular inspection of capacitor installations should include a check of bushings, ventilation, fuses, voltages, and ambient temperature as well as a cleaning of surfaces for removal of dust or other foreign material. It is particularly important that bushings and other insulating surfaces be kept clean. Capacitors that are leaking insulating fluid should be taken out of service immediately. If minor, the leak may be soldered over; major leaks, broken bushings, or other internal or external damage can best be repaired in the shop or factory. |

| Rectifiers |

| Function.. |

| A rectifier is a device that converts alternating current into a unidirectional current by virtue of a characteristic that permits an appreciable flow of current in only one direction. More popularly, it is a device that converts ac to dc. |

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