Rated voltage
The term rated voltage has been used in electrical power engineering in accordance with DIN 40200 since 1981 in order to make it possible to distinguish it from the nominal voltage, to better clarify this in the standards and to apply the terms uniformly. Previously, the term nominal voltage was generally used ambiguously . It was created as a coordinated translation of the English term rated value / rated voltage of the IEC , as there was no suitable word for it in German. He is thus aligning the terms with DIN 55350-12 , which also describes non-electrical values more comprehensively.
The rated voltage is defined as
"A value of a quantity applicable for a given operating condition, which is generally determined by the manufacturer for an element, a group or a device."
This designation is therefore used in most cases for the identification of electrical equipment . The designation also enables various rated values to be related and rated data = "Compilation of rated values and operating conditions" to be defined or determined, for example: rated power or rated current at rated voltage (and rated frequency).
Nominal and rated values can be equal in value, but a rated voltage is in most cases equal to or greater than the rated voltage. While the nominal voltage represents a generalized designation (an identifier ), the rated voltage describes the basic construction data of the equipment.
Example 1:
- The nominal voltage of an electrical network is 10 kV, which is the name of this network.
- The rated voltage of equipment used within the distribution network such as B. transformers , circuit breakers and isolators is generally 12 kV, which is 20% above the nominal voltage of the network and which results largely from the insulation used.
- The rated voltage of specific consumers such as B. directly coupled high-voltage machines is generally 10 kV, which corresponds to the nominal voltage of the network. The defined rated voltage is decisive for the specified rated power.
Example 2:
- The nominal voltage of an electrical network is 230 V, which is the single-phase line voltage of the underlying 400 V three-phase network and actually corresponds to a voltage of 231 V.
- The rated voltage of the cables used is generally 300 V ( e.g. H03 ... ).
- The rated voltage of the switching elements used is generally 250 V.
- The rated voltage of the radio interference suppression capacitors used is generally 250 V or 300 V.
In earlier times, the rated voltage was often called "upper nominal voltage" in order to show the corresponding upper voltage tolerances for the equipment or to cover different nominal voltages of networks regardless of the "nominal voltage of the equipment". Today, voltage tolerances are basically defined by the manufacturer as dimensioning tolerances depending on the rated voltage and independent of the nominal voltage and result in the respective upper and lower limit value = "The largest or smallest permissible value of a variable contained in a specification.". The determination of the rated voltage depending on the nominal voltage of networks therefore often has historical reasons and / or enables the use of equipment with different, differing nominal voltages of networks, for example in different countries (e.g. 220 V, 230 V, 240 V) .