The following details shows the typical name plate details of a transformer
Power rating (1000 KVA) : It indicates that the transformer is able to supply 1000 KVA of load without any problem.
H.V rating (21KV): This is the maximum high voltage side voltage with it can withstand. If the applied voltage is higher than 10% of rated voltage then transformer core saturation may occur.
L.V rating (6.6KV): This is the rated secondary line voltage of the transformer.
Frequency (60Hz): The rated frequency of the transformer with it can operated. The transformer can be operated above the rated frequency but it cannot be operated below.
%impedance: It indicates the amount of voltage drop from the no-load current to full load current.
Tap voltages: This parameter specifies the rated voltage for each tap that the transformer can provide.
Type of transformer: power transformer, distribution transformer, instrumentation transformer etc.
Winding connection diagram: This diagram shows the primary and secondary winding connection diagram.
Cooling class (ONAF): This indicates of type of cooling used in transformer. For example ONAF indicates that it is Oil Natural and Air Forced type cooling.
Rated temperature (600): The maximum rated temperature that the transformer can be operated without any heating.
In-addition to the above the name plate also contains about weight of the transformer, volume of the oil, type of insulating material etc.