nominal voltage

The nominal voltage (rarely also called nominal voltage ) of an electrical consumer or a voltage source ( battery , generator , power grid ) is the value of the electrical voltage specified by the manufacturer or supplier in normal operation. The term nominal voltage has been defined in DIN 40200 since 1981 . It must be completely differentiated from the rated voltage, especially for electrical equipment and consumers . The terms are also coordinated with DIN 55350-12 , which also describes non-electrical values more comprehensively.

The nominal voltage is

"A suitable rounded value of a quantity to designate or identify an element, group or institution."

It is a generalized name, an identifier . It is mainly used to mark voltage sources such as batteries or electrical networks . Use with equipment, consumers, electronic components or the like is generally only common within a type designation. On the other hand, the rated voltage describes or describes the basic design data. Accordingly, technical data are always rated values. The undefined but sometimes used term “nominal voltage ” also represents a rated voltage, as it relates to defined operating conditions (a defined rated environment).

Nominal voltage of electrical sources

The nominal voltage is generally a principle-related variable or a variable derived from the rms value of the voltage. Tolerances or specific operating conditions are ignored. The star voltage or phase voltage is used in single-phase networks . In three-phase networks, on the other hand, the linked voltage or (external) conductor voltage . It is not absolutely necessary to specify the star voltage or line voltage (690 V = 690 V / 400 V or 400 V = 400 V / 230 V), but can be specified in particular for non-standard voltages (e.g. 220 V / 127 V) . The specific designation depends on the point of view of the observer and on the rounding of the value. The designations 690 V and 0.7 kV are equivalent . The single-phase line voltage of 231 V of the underlying 400 V three-phase network is usually referred to as 230 V.

Nominal voltage of batteries

For batteries and accumulators , the nominal voltage is a suitable, approximate value of the voltage for identifying a cell, a battery or an electrochemical system (according to DIN EN 60050-482). The no-load voltage is always higher than the nominal or rated voltage. The nominal voltage of a battery results from the number of cells connected in series.

The nominal voltage per cell of batteries (not rechargeable) and accumulators (rechargeable) is:

1.2 V for the nickel-cadmium cell (see nickel-cadmium battery ), the nickel-metal-hydride cell (see nickel-metal-hydride battery ) and the nickel-iron cell (see nickel-iron -Battery )
1.35 V for the mercury-zinc cell, see mercury-zinc battery
1.5 V for the alkaline manganese cell, see alkaline manganese battery
1.5 V for the zinc-carbon cell, see zinc-manganese dioxide cell
1.5 V for the zinc-air cell, see zinc-air battery
1.5 V for the lithium iron sulfide cell, see lithium iron sulfide battery
1.55 V for the silver oxide-zinc cell, see silver oxide-zinc battery
2.0 V for the lead dioxide lead cell (see lead accumulator )
2.9 to 3.7 V for lithium cells, depending on the cathode material, see lithium battery or lithium accumulator

Nominal value of the mains voltage

In Europe, the nominal value of the mains alternating voltage is 230 V (outer conductor / neutral conductor, single-phase alternating current ) or 400 V (outer conductor / outer conductor, three-phase current ). That is the rms value . The nominal value of the frequency is 50 Hz. Until 1987 the nominal value was 220 volts in continental Europe and 240 volts in the United Kingdom . The transition period was actually 20 years, but it is still not fully completed. Electrical consumers specified for 220 V can usually also be operated at the 4.5% higher voltage. The energy consumption for unregulated linear consumers does not increase by 4.5%, but by a little more than 9% because of the quadratic dependency.

In the USA, the nominal value of the AC mains voltage is 120 volts. For fluorescent lamps (burning voltage up to approx. 110 V required plus ballast) and larger consumers such as air conditioning systems and washing machines, double the voltage of 240 V is also used; the relationship results from the single-phase three-wire network common in the USA . The mains frequency is 60 Hz.

In the USA, a classic distinction is made between distribution voltage (= distribution voltage ) as the output voltage of the feeding transformers and utilization voltage (= consumer voltage ). This means, for example, that the nominal voltage of the network is 120 V, while the nominal voltage of the loads is 115 V. The corresponding three-phase networks with a distribution voltage of 208 V / 120 V result in a utilization voltage of 200 V / 115 V.

Historically, the 110 and 220 V go back to the fact that just 55 volts DC is sufficient for the operation of carbon arc lamps (street lighting, film projectors). At higher voltages there is a risk of electric shock and power would have been unnecessarily lost in the required series resistance of the arc lamps. This also meant that transformers were needed to set up the power grid, and the DC voltage used initially was switched to AC voltage.

Other nominal voltages

Vehicles and planes

bicycle

6 volts alternating voltage ( bicycle dynamo , variable frequency, rated load 3 watts)

Motor vehicles (DC voltage)

6 volts (older cars and motorcycles, end-of-charge voltage and thus the on-board voltage is 7.2 volts)
12 volts (cars, motorcycles , end-of-charge voltage and thus the on-board voltage is 14 volts)
24 volts ( truck , end-of-charge voltage and thus the on-board voltage is 28 volts), the so-called automotive tolerance range is 18 ... 30 volts

Aircraft (selection)

28 volts DC voltage (22 ... 29 volts)
115/200 volts three-phase current / 400 Hz (108 ... 118 volts RMS)
± 270 volts DC voltage (250 ... 280 volts)

Railway vehicles

24 volt direct current (mainly railcars, tolerance range is 16.8 ... 30 V)
36 volts DC voltage (previously used in Switzerland for all vehicles control voltage)
74 volts DC voltage (control voltage for American vehicles)
110 volts DC voltage (mainly locomotives, tolerance range is 77 ... 137.5 V)
1000 volts alternating current / 16.7 Hz ( train busbar )

Control voltages

Direct voltage (DC) or alternating voltage (AC) is used as control and operating voltage within electrical systems.

Industrial plants

Usual nominal voltages: 24 V DC, 24 V AC, 42 V AC.

Switchgear

Voltages of 100 V AC (output voltage from voltage converters ), 110 V AC or DC, 220 V AC or DC are common.

telecommunications

Telephone terminal connection: 60 V DC voltage
Switching systems: 48 V direct voltage (operating voltage)
Tube output stages from large transmitters: 12 kV DC voltage

Power distribution networks

Low voltage (<1 kV)

115 volts
230 volts
400 volts
500 volts
690 volts

Medium voltage (1–35 kV)

6 kV
10 kV
15 kV (also standard voltage of the overhead line of electric railways of the DB, SBB and ÖBB)
20 kV
30 kV

Since numerous older underground cables (mostly for 6 kV and 10 kV) have been laid in many cities, the lower values are common in many city networks. In rural areas, 20 kV and 30 kV are mostly used.

High voltage

60 kV (in Germany almost only in city networks with a high proportion of older cables)
66 kV (rated voltage in the SBB traction network)
110 kV (also rated voltage in the traction network in Germany and Austria)
132 kV (nominal voltage in the SBB traction network)

High voltage

(→ Voltage specifications for high-voltage lines )

220 kV / 230 kV (since the 1920s)
380 kV / 400 kV (European network; since 1952 Harsprånget - Hallsberg in Sweden, 1957 in Germany)

Outside Europe, other nominal voltages are sometimes common. In other countries there are often relatively short test leads. Frequent values in high and extra high voltage networks are:

66 kV
132 kV
275 kV
345 kV
420 kV
500 kV
735 kV (since 1965 in Québec, Canada)
750 kV (since the 1980s in Russia and from there to neighboring countries)
765 kV (since 1967, mainly Russia, USA, Canada, South Africa, Brazil)
1100 kV ( three-phase line Kita-Iwaki in Japan, currently operated with 500 kV)
1150 kV ( three-phase line Ekibastus – Kökschetau in Kazakhstan, mostly operated with about half)

There are no nominal voltages for high-voltage direct current transmission systems, as there are almost always two-point connections. Frequently selected voltage values for modern systems are: