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Page 39

| Transformers With More Than Two Windings |

| Under special circumstances, transformers have been constructed with three or four windings, Sometimes, the coil arrangement for the normal two-winding transformer provides for two separate coils to constitute the secondary winding. The construction details described above apply equally to these multi-winding types. |

| Single- And Three-Phase Transformers |

| In general, the same construction details described above for single-phase transformers also apply to three-phase transformers. These latter usually consist of three single-phase units within the same enclosure or tank. However, when advantage is taken of the combination of cores, the three separate sets of windings are wound on a three-legged core. Three-phase transformers similar to the one illustrated in Fig. 2-21 are often used in the larger sizes for substation and industrial use, principally because of the savings in space and weight, and hence cost. |

| Figure 2-21 Substation transformer. |

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