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Direct Current (DC) Power: definition and applications

Direct Current (DC) Power refers to the unidirectional flow of electrons and is the form of power that is most commonly produced by sources such as solar cells and batteries.

What is power?

Power can be defined as the rate of energy consumed in a unit time. The unit of measurement of power is Watt, after the famous eighteenth century scientist, James Watt who invented the steam engine. In mechanical systems, power is known as mechanical power and is a combination of forces and movement. In electrical systems, electrical power is the rate of flow of electrical energy past a given point in a closed circuit. For our applications we will only consider the electrical power.

Alternating and direct current

Electrical power can be classified as AC Power or DC Power depending upon the direction of the flow of energy. Here AC stands for Alternating Current and DC stands for Direct Current. Power which is a result of current flowing in alternating direction is termed as AC Power and one which is a result of current flowing in only one direction is called DC Power.

Direct current waveform

In DC (Direct current) circuits, the flow of electrical charge (or in other words, electrons) is unidirectional and unlike AC Current, it does not periodically reverses its direction. The typical waveform of alternating current is a pure sine wave as shown in the figure below.  
Different types of Current, AC, DC,

Direct Current (red curve). The horizontal axis measures time; the vertical, current or voltage. Source:

What are common DC applications?

This form of power is most commonly produced by sources such as solar cells, batteries, and thermocouples. DC power is widely used in low voltage applications such as charging batteries, automotive applications, aircraft applications and other low voltage, low current applications. All solar panels nowadays produce DC power. Common applications with DC power in the PV industry are portable solar systems and other off-grid appliances. Not using a solar inverter to convert DC to AC will keep the costs down for such systems.

Advantages and Disadvantages DC current

Nowadays for electric power distribution alternating current is mostly used, as it has significant advantages over direct current in transmission and transforming. One of the biggest advantages of DC power is its ability to be used in special applications. Whenever AC power transmission is not practically feasible or possible over long distances, DC power is used. One such application are sub-sea high voltage DC transmission lines. Here, the electricity is produced in AC form, converted to DC at a switching/ terminal station, transmitted by a subsea network of cables, re-converted to AC by another terminal station and finally delivered to customers.
Norned Direct Current cable

Norned DC cable between Norway and The Netherlands Source: Wikipedia


Sub-Sea DC Transmission Lines

Many such lines are functional to date. Some notable examples are:
  • Baltic Cable Link
    • Between: Sweden and Germany
    • Length: 250 km
  • NorNed Cable Link
    • Between: Norway and Netherlands
    • Length: 580 km
  • Basslink
    • Between: Australian mainland and Tasmania
    • Length: 290 km
A big disadvantage of these High Voltage Transmissions is the higher cost of building terminal stations and switching yards. The parts used need quite a lot of maintenance, which is expensive, and have limited overloading capacity as well.
Laxmikant Vishnu Desai

Laxmikant Vishnu Desai

on 01 Feb 2019


Saleem Merchant

Saleem Merchant

on 15 May 2018

Lost to understand, despite of very low cost due to energy-efficient, why it does not frequently use in homes, specially where source of energy is solar power.



on 11 Apr 2018

Because it is direct, hence Direct Current (DC)



on 30 Jan 2018

Driver in put DC 440v then drive output 3pase ?

shahid shafi

shahid shafi

on 04 Jun 2017

Why a.c has name as a.c ??? Its reason is based on the fact of direction ... In USA the alternating current has frequency of 60Hertz which means the the coil rotates 60Times and in each rotation/Rearly revolution the direction of current changes 120 times... But Why D.C...has Name As d.c

pabitra sarkar

pabitra sarkar

on 20 Mar 2017

I like it

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