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Page 40

| Portable Transformers |

| Transformers, especially larger power units, have been mounted on wheels, as shown in Fig. 2-22, for temporary operation in emergencies or for maintenance. These are equipped with protective devices and are sometimes referred to as portable or movable substations. |

| Figure 2-22 Portable transformer. |

| Tanks... |

| Transformer tanks vary in size and shape depending on the manufacturer and the age of the transformer. The older transformers have heavy cast-iron cases, but the later ones are made of welded sheet steel. The tank holds the core, windings, bushings, and leads in position, and must be oil tight to hold the oil that insulates and cools the transformer. The tanks have fittings in the back, so that crossarms or hangers may be attached for erecting the transformers on a pole. Lifting lugs are provided on the sides for handling the unit. The nameplate and connection diagram showing the location of the leads from the windings is attached outside the tank. A cover and gasket to prevent foreign substances from entering the transformer and to keep rain from causing rust and corrosion, and deterioration of the insulating materials, is securely held in place by bolts or clamps. A grounding lug is usually installed near the bottom of each tank so that it can be electrically grounded for safety purposes when installed. |

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