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Page 19

| Figure 1-17 Networking or banking of transformers. |

| The conventional power transformer is designed to operate with the primary connected across a constant potential source and to provide a secondary voltage that is substantially constant from no load to full load. |

| Like any other piece of equipment, the efficiency of a transformer is given by: |

| Transformer Ratings |

| The capacity of a transformer is limited by the permissible temperature rise. Both the current and the voltage contribute to determine the heat generated in a transformer. As has been shown above, because of reactance, the current and the voltage waves do not always act in concert, and the power supplied (as expressed in watts) is not always a measure of the heat generating processes. Hence, the rating of a transformer is expressed as a product of the volts and amperes, or volt-amperes (for practical purposes, kVA is used). For a given power factor of load, these values often are used interchangeably. |

| Figure 1-18 (on page 20) illustrates the nameplate on a transformer giving all the pertinent information required for the proper operation and maintenance of the unit. The capacity of a transformer (or any other piece of electrical equipment) is limited by the permissible temperature rise during operation. The heat generated in a transformer is determined by both the current and the voltage. Of more importance is the kilovolt-ampere rating of the transformer. This indicates the maximum power on which the transformer is designed to operate under normal conditions (when the current and voltage are in phase). Other information generally given is the phase (single-phase, three-phase, etc.), the primary and secondary voltages, frequency, the permitted temperature rise, the cooling requirementswhich include the number of gallons of fluid that the cooling tank may hold. Primary and secondary currents may be stated at full load. |

| Depending upon the type of transformer and its special applications, |

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