Which electricity is natural alternating current or direct current

Direct current

Lexicon> letter G> direct current

Acronym: DC

Definition: electrical current that always flows in the same direction

Counter-term: alternating current

English: direct current

Category: electrical energy

Author: Dr. Rüdiger Paschotta

How to quote; suggest additional literature

Original creation: 04/26/2010; last change: 03/14/2020

URL: https://www.energie-lexikon.info/gleichstrom.html

Direct current is an electric current that always flows in the same direction - unlike alternating current. Is accordingly DC voltage an electrical voltage with a constant direction. However, the amounts of voltage and current do not necessarily have to be constant; you can z. B. pulsate in strength.

Direct current can be generated with batteries, fuel cells and photovoltaic modules, but also with direct current generators. It is needed z. B. to operate electronic devices, DC motors and electrolysis.

Direct current can be obtained from alternating or three-phase current with the help of Rectifiers be won. Reversing can be made from direct current with the help of Inverters AC or three-phase current can be produced again, although the technology here is somewhat more complex and lossy than that of rectifiers. At least large converters and rectifiers can, however, be implemented with very high energy efficiency.

Direct current in competition with alternating current

In the early days of electrification there was a tough battle over the question of whether the power grids to be built should be based on direct current or alternating current. Thomas Edison championed his concept of the direct current network, among other things by pointing out the higher risk of electric shock with alternating current. Nonetheless, Westinghouse's AC grid concept prevailed, even though DC itself would be the “natural solution” for most consumers. The main reason for this is that alternating current can easily be brought to other voltage levels using transformers. This option was not available for direct current at the time. Today, however, modern power electronics offer attractive and efficient solutions for this. That is why there are increasing attempts to use the advantages of direct current:

Wasn't Edison right that using direct current would be cheaper?
  • Today, high-voltage lines mostly work with three-phase current, i.e. three-phase alternating current. For point-to-point connections over long distances with high power, however, high-voltage direct current transmission (HVDC) is also increasingly used. This avoids various problems such. B. with reactive currents (especially with submarine cables) and enables transmission with lower energy losses. Energy can also be exchanged between different AC networks in a simple manner without having to synchronize the frequency. Even a supergrid, in this case a meshed power grid, would most likely work with direct current.
  • Efforts are also being made to use new systems for direct current operation for the local distribution of electrical energy. Even if direct current has to be obtained from the alternating current with a rectifier, this is more efficient than using individual rectifiers for many small devices. The direct current concept seems to have particular opportunities for special applications such as data centers, in which a battery-supported uninterruptible power supply with direct current can be implemented much more easily and with less loss, i.e. also with less energy.

The general conversion of the network to direct current, on the other hand, appears to be an extremely difficult task, as a great deal of the existing infrastructure would have to be converted at great expense. On the other hand, it is entirely possible that increasingly small sub-networks for direct current will be set up, for example in connection with the increasing use of photovoltaics and electric cars.

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See also: electrical current, electrical voltage, electrical energy, alternating current, three-phase current, rectifier, power grid, high-voltage line, high-voltage direct current transmission
as well as other items in the electrical energy category