(1) Rated capacity (SN)
The rated capacity is the guaranteed value of the apparent power output by the transformer under the rated working condition (ie, working condition under the rated voltage, rated frequency, and rated service conditions) specified by the manufacturer and expressed as SN.
The rated capacity usually refers to the capacity of the high voltage winding; when the transformer capacity changes due to the cooling method, the rated capacity refers to its maximum capacity.
(2) Rated current (I1, I2)
The primary and secondary rated currents of the transformer refer to the line currents that the first and second windings of the transformer are not allowed to over-temperature under rated voltage and rated ambient temperature for a long period of time. The unit is denoted by A.
3) Rated voltage (UN)
The rated voltage of the transformer is the rated voltage of each winding and refers to the voltage that is generated when the rated or no-load is applied. The primary rated voltage U1N refers to the rated voltage value of the transformer primary winding terminal; the secondary rated voltage U2N refers to when the primary winding voltage is rated and the tap-changer is placed on the rated tap contact, and the transformer is empty. The voltage of the secondary winding (in V or KV). The rated voltage of a three-phase transformer refers to the line voltage.
In general, appropriate taps are drawn on the high voltage windings because the high voltage windings or their individual voltage regulator windings are often placed on the outermost side to facilitate tapping; secondly, the high voltage side current is small and the tap leads and the tap changer are loaded. The cross section of the flow section is small, and the contact portion of the tap changer is easily solved.