The rated characteristic shall be such that the transformer can supply rated current under a constant load condition, without exceeding the limits of temperature increase, provided that the applied voltage is assumed to be equal to the nominal voltage and nominal frequency. Boston Gear BG11-1-4-4
The nominal characteristic consists basically of the following values:
– nominal winding powers;
– nominal winding voltages;
– nominal winding currents;
– nominal frequency;
– insulation levels of the windings.
Transformers may be overloaded in accordance with NBR 5416. Auxiliary equipment such as bushings, on-load tap-changers and others shall withstand overloads corresponding to up to one-and-a-half times the nominal power of the transformer. When overcharging conditions other than those mentioned above are to be expected, the manufacturer must be informed.
Unless otherwise specified, the transformers shall be capable of operating at the main branch at a voltage other than the rated voltage under the conditions laid down. The nominal frequency is 60 Hz.
The condition of insulation level, air spacings and other items must comply with the established in NBR 5356-3, which establishes the insulation level of the transformers.