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| Oil-filled units. Since oil-filled units are usually enclosed in steel tanks very similar to transformers, a shield is provided between the coils and tank. The shield is usually made of varnished steel laminations to hold down eddy currents and tends to concentrate the magnetic field within the reactor coil. As a result, fewer turns may be required in the reactor winding to produce the desired reactance. |

| Operation |

| Reactors are placed in series with the equipment or circuits to be protected. Air-core units are employed for voltages to 34.5 kV; oil-immersed units are used for higher voltages. Ratings of reactors are expressed in the amount of kVA absorbed at rated current and voltage. The reactance is expressed as a percentage, that is, the voltage drop across the reactor at rated current. For example, in a 20,000-kVA, three-phase, 14,400-V circuit, a 6-percent reactor would be rated 1,200 kVA or 400 kVA single-phase. The drop would be 6 percent of 14,000 × 0.866 (for single-phase), or 500 V at 800 amperes (400 kVA divided by 800 amperes). The reactance would be 500 volts divided by 800 amperes, or 0.625 ohm. |

| Reactors are sometimes installed in series with transformers when transformers of dissimilar characteristics are paralleled in order to obtain an equitable distribution of load between them. The saturable iron-core reactor is used to control the value of inductive reactance (in theater lighting, for example). |

| Maintenance |

| Little maintenance is required for reactors. Care should be taken to keep the cooling paths for both air and oil units clear. Conductors and supports should be examined periodically for cracks or other signs of excess stress. Connections should be checked for tightness. |

| Capacitors. |

| Function |

| A capacitor is a device for introducing capacitance or capacitive reactance in a circuit, its primary purpose being to counteract the effects of inductive reactance. It reduces the impedance of a circuit with a consequent reduction in the voltage drop and an improvement in the power factor. By reducing the current required to supply a given load, it decreases losses in the circuit. |

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