Nominal value
The nominal value as defined by DIN 40200 is a suitable rounded value of a quantity for designating or identifying a component, device or equipment. The following application areas can be categorised using the nominal value of a quantity.
Application areas
- Nominal diameter (DN), e.g. DN 100
- Nominal pressure (PN), e.g. PN 16
- Nominal speed (nN), e.g. nN = 2,900 min–1 (rpm)
(rated speed) - Nominal voltage, e.g. 230 V
Voltage of a mains supply - Rated voltage (of equipment) from the manufacturer for a defined operating condition of a component, device, or piece of equipment
The quantity actually used does not need to be identical to the nominal value but can approximate it. There are scenarios in which the nominal and rated value are one in the same.
In this case, the term that applies must be defined. A synchronous motor designed for a speed of 3,000 min-1 (rpm) at 50 Hz will, at this frequency, always run at 3,000 min-1.
The user views this speed as well as that of the machine driven directly by the synchronous motor as the "nominal speed" because the rounded numerical value for designation and identification purposes is suited to daily use. This speed is also regarded as the "rated speed", since it establishes the basis for designing and rating the motor. It is in this context that the nominal speed is no longer the speed agreed on in the supply contract (as previously), but a classification speed (e.g. 2,900 min–1 (rpm)).
