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Split-phase electric power

A split-phase or single-phase three-wire system is a type of single-phase electric power distribution. It is the AC equivalent of the original Edison three-wire direct-current system. Its primary advantage is that it saves conductor material over a single-ended single-phase system, while only requiring a single phase on the supply side of the distribution transformer.[1]

Fig. 3. Pole-mounted single-phase transformer with three-wire center-tapped "split-phase" secondary.One side of the primary is connected to ground. On the three secondary terminals, the center tap is also grounded with a short strap to the transformer case.

Fig. 1
Fig. 2

A transformer supplying a three-wire distribution system has a single-phase input (primary) winding. The output (secondary) winding is center-tapped and the center tap connected to a grounded neutral. As shown in Fig. 1. either end to center has half the voltage of end-to-end. Fig. 2 illustrates the phasor diagram of the output voltages for a split-phase transformer. Since the two phasors do not define a unique direction of rotation for a revolving magnetic field, a split single-phase is not a two-phase system.

In the United States, the practice originated with the DC distribution system developed by Thomas Edison. By connecting pairs of lamps or groups of lamps on the same circuit in series, and doubling the supply voltage, the size of conductors was reduced substantially.

The line to neutral voltage is half the line-to-line voltage. Lighting and small appliances are connected between a line wire and the neutral. Large appliances, such as cooking equipment, space heating, water pumps, clothes dryers, and air conditioners are connected across the two line conductors, requiring less current and smaller conductors than would be needed if the appliances were designed for the lower voltage. [2]

Fig. 4
Fig. 5

If the load were guaranteed to be balanced, then the neutral conductor would not carry any current and the system would be equivalent to a single-ended system of twice the voltage with the line wires taking half the current. This would not need a neutral conductor at all, but would be wildly impractical for varying loads; just connecting the groups in series would result in excessive voltage and brightness variation as lamps are switched on and off.

By connecting the two lamp groups to a neutral, intermediate in potential between the two live legs, any imbalance of the load will be supplied by a current in the neutral, giving substantially constant voltage across both groups. The total current carried in all three wires (including the neutral) will always be twice the supply current of the most heavily loaded half.

For short wiring runs limited by conductor ampacity, this allows three half-sized conductors to be substituted for two full-sized ones, using 75% of the copper of an equivalent single-phase system.

Longer wiring runs are more limited by voltage drop in the conductors. Because the supply voltage is doubled, a balanced load can tolerate double the voltage drop, allowing quarter-sized conductors to be used; this uses 3/8 the copper of an equivalent single-phase system.

In practice, some intermediate value is chosen. For example, if the imbalance is limited to 25% of the total load (half of one half) rather than the absolute worst-case 50%, then conductors 3/8 of the single-phase size will guarantee the same maximum voltage drop, totalling 9/8 of one single-phase conductor, 56% of the copper of the two single-phase conductors.

Balanced power

In a so-called balanced power system, an isolation transformer with a center tap is used to create a separate supply with conductors at a balanced Vnom/2 with respect to ground. The purpose of a balanced power system is to minimize the noise coupled into sensitive equipment from the power supply.

Unlike a three-wire distribution system, the grounded neutral is not distributed to the loads; only line-to-line connections at 120 V are used. A balanced power system is only used for specialized distribution in audio and video production studios, sound and television broadcasting, and installations of sensitive scientific instruments.

The U.S. National Electrical Code provides rules for technical power installations.[3] The systems are not to be used for general-purpose lighting or other equipment, and may use special sockets to ensure only approved equipment is connected to the system. Additionally, technical power systems pay special attention to the way the distribution system is grounded.

A risk of using a balanced power system, in an installation that also uses "conventional" power in the same rooms, is that a user may inadvertently interconnect the power systems together via an intermediate system of audio or video equipment, elements of which might be connected to different power systems.


In Europe, three-phase 230/400 V is most commonly used. However, 230/460 V, three-wire, single-phase systems are used to run farms and small groups of houses when only one (or sometimes two) of the three-phase high-voltage conductors are available. A split-phase final step-down transformer is often used, with the centre-tap earthed and the two halves usually supplying different buildings.

In the UK, electric tools and portable lighting at construction sites are required to be fed from a centre-tapped system with only 55 V between live conductors and the earth. This system is used with 110 V equipment and therefore no neutral conductor is needed. The intention is to reduce the electrocution hazard that may exist when using electrical equipment at a wet or outdoor construction site. Portable transformers that transform single-phase 240 V to this 110 V system are a common piece of construction equipment. Generator sets used for construction sites are equipped to supply it directly.

An incidental benefit is that the filaments of 110 V incandescent lamps used on such systems are thicker and therefore mechanically more rugged than those of 240 V lamps.


In Australia and New Zealand, remote loads are connected to the grid using SWER (single-wire earth return) transmission lines, since it is cheapest to run only one wire. The primary of the transformer is connected between the high voltage line and earth, the secondary is a three-wire single-phase system as described here, the secondary voltage being 230/460 V. Single phase loads are split between the two circuits. Hot water services use both circuits.

North America

This three-wire single phase system is common in North America for residential and light commercial applications. In this case, the voltages are 120 V line to neutral (grounded center tap of transformer) and 240 V line to line. This system allows 120 volts to be supplied for lighting and convenience outlets, and 240 volts for higher-demand appliances such as space heating, air conditioning, kitchen stoves or water heaters. Wiring regulations govern the application of split-phase circuits; since the neutral (return) conductor is not protected by a fuse or circuit breaker, a neutral wire can be shared only by circuits fed from opposite lines of the supply system. Two circuits from opposing lines may share a neutral if both breakers are connected by a bar so that both trip simultaneously ([4] NEC 210.4), this prevents 120 V from feeding across 240 V circuits.


In Sweden split-phase electric power is also used on some railways. The center tap is grounded, one pole is fed with an overhead wire section, while the other wire is used for another section.

Amtrak's 60 Hz traction power system in the Northeast Corridor between New York and Boston also uses split-phase power distribution. Two separate wires are run along the track, the contact wire for the locomotive and an electrically separate feeder wire. Each wire is fed with 25 kV with respect to ground, with 50 kV between them. Autotransformers along the track balance the loads between the contact and feeder wires, reducing resistive losses.

In the UK Network Rail are using autotransformers on all new 50 Hz electrification, and (as of 2014) are converting many old booster transformer [1] installations to autotransformers, to reduce energy losses [2] and exported electromagnetic interference, both of which increase when longer, heavier, or faster trains are introduced, drawing higher peak current from the supply. Note that booster transformers only "boost" the return of traction current through its intended path, the "return conductor", rather than randomly through the earth, and do not boost, but rather reduce, the available voltage at the train, and introduce additional losses. The autotransformer system enforces the traction return current taking its intended path, while reducing the transmission losses, and therefore achieves both required objectives, of controlling return current leakage to earth and ensuring low energy loss, simultaneously. There is an initial cost penalty, because the previous return conductor, insulated to a fairly modest voltage, must be replaced by an anti-phase feeder, insulated to 25 kV, and the autotransformers themselves are larger and more expensive than the previous booster transformers.

See also
  1. Terrell Croft and Wilford Summers (ed), American Electricians' Handbook, Eleventh Edition, McGraw Hill, New York (1987) ISBN 0-07-013932-6, chapter 3, pages 3-10, 3-14 to 3-22.
  2. Gonen, Turan. Electric Power Distribution System Engineering, 2nd ed. CRC Press, 2007, p. 284.
  3. NFPA 70, National Electrical Code 2005, National Fire Protection Association, Inc., Quincy, Massachusetts USA, (2005). no ISBN , articles 640 and 647
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Split-phase electric power


A split-phase or single-phase three-wire system is a type of single-phase electric power distribution. It is the AC equivalent of the original Edison three-wire direct-current system. Its primary advantage is that it saves conductor material over a single-ended single-phase system, while only requiring a single phase on the supply side of the distribution transformer. Fig. 3. Pole-mounted single-phase transformer with three-wire center-tapped "split-phase" secondary.One side of the primary is connected to ground. On the three secondary terminals, the center tap is also grounded with a short strap to the transformer case. Connections Fig. 1 Fig. 2 A transformer supplying a three-wire distribution system has a single-phase input (primary) winding. The output (secondary) winding is center-tapped and the center tap connected to a grounded neutral . As shown in Fig. 1. either end to center has half the voltage of end-to-end. Fig. 2 illustrates the phasor diagram of the output voltages for a split-phase transformer ...more...

Three-phase electric power


Three-phase electric power is a common method of alternating current electric power generation , transmission , and distribution . It is a type of polyphase system and is the most common method used by electrical grids worldwide to transfer power. It is also used to power large motors and other heavy loads. A three-wire three-phase circuit is usually more economical than an equivalent two-wire single-phase circuit at the same line to ground voltage because it uses less conductor material to transmit a given amount of electrical power. The two-phase system was independently invented by Galileo Ferraris , Mikhail Dolivo-Dobrovolsky , Jonas Wenström , John Hopkinson and Nikola Tesla in the late 1880s. Principle Normalized waveforms of the instantaneous voltages in a three-phase system in one cycle with time increasing to the right. The phase order is 1‑2‑3. This cycle repeats with the frequency of the power system. Ideally, each phase’s voltage , current, and power is offset from the others’ by 120°. Three-pha ...more...

Single-phase electric power


A single-phase polemount stepdown transformer in Canada. One supply phase (phase-to-neutral) from the utility is converted to split-phase for the customers. In electrical engineering, single-phase electric power is the distribution of alternating current electric power using a system in which all the voltages of the supply vary in unison. Single-phase distribution is used when loads are mostly lighting and heating, with few large electric motors. A single-phase supply connected to an alternating current electric motor does not produce a revolving magnetic field; single-phase motors need additional circuits for starting (capacitor start motor), and such motors are uncommon above 10 kW in rating. Because the voltage of a single phase system reaches a peak value twice in each cycle, the instantaneous power is not constant. A single-phase load may be powered from a three-phase distribution transformer in two ways: by connection between one phase and neutral or by connection between two phases. These two give diff ...more...

Two-phase electric power


A simplified diagram of a two-phase alternator Two-phase electrical power was an early 20th-century polyphase alternating current electric power distribution system. Two circuits were used, with voltage phases differing by one-quarter of a cycle, 90°. Usually circuits used four wires, two for each phase. Less frequently, three wires were used, with a common wire with a larger-diameter conductor. Some early two-phase generators had two complete rotor and field assemblies, with windings physically offset to provide two-phase power. The generators at Niagara Falls installed in 1895 were the largest generators in the world at that time and were two-phase machines. Three-phase systems eventually replaced the original two-phase power systems for power transmission and utilization. There remain few two-phase distribution systems, with examples in Philadelphia , Pennsylvania ; many buildings in Center City are permanently wired for two-phase and Hartford, Connecticut . Comparison with single-phase power The advantage ...more...

Electric power distribution


A 50 kVA pole-mounted distribution transformer Electric power distribution is the final stage in the delivery of electric power ; it carries electricity from the transmission system to individual consumers. Distribution substations connect to the transmission system and lower the transmission voltage to medium voltage ranging between 2  kV and 35 kV with the use of transformers . Primary distribution lines carry this medium voltage power to distribution transformers located near the customer's premises. Distribution transformers again lower the voltage to the utilization voltage used by lighting, industrial equipment or household appliances. Often several customers are supplied from one transformer through secondary distribution lines. Commercial and residential customers are connected to the secondary distribution lines through service drops . Customers demanding a much larger amount of power may be connected directly to the primary distribution level or the subtransmission level. History The late 1870s and ...more...

Electric power system


An electric power system is a network of electrical components deployed to supply, transfer, store, and use electric power. An example of an electric power system is the grid that provides power to an extended area. An electrical grid power system can be broadly divided into the generators that supply the power, the transmission system that carries the power from the generating centres to the load centres, and the distribution system that feeds the power to nearby homes and industries. Smaller power systems are also found in industry, hospitals, commercial buildings and homes. The majority of these systems rely upon three-phase AC power —the standard for large-scale power transmission and distribution across the modern world. Specialised power systems that do not always rely upon three-phase AC power are found in aircraft, electric rail systems, ocean liners and automobiles. History A sketch of the Pearl Street Station In 1881, two electricians built the world's first power system at Godalming in England. It ...more...

Induction motor


Cutaway view through stator of TEFC induction motor, showing rotor with internal air circulation vanes. Many such motors have a symmetric armature, and the frame may be reversed to place the electrical connection box (not shown) on the opposite side. An induction motor or asynchronous motor is an AC electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding. An induction motor can therefore be made without electrical connections to the rotor. An induction motor's rotor can be either wound type or squirrel-cage type. Three-phase squirrel-cage induction motors are widely used as industrial drives because they are rugged, reliable and economical. Single-phase induction motors are used extensively for smaller loads, such as household appliances like fans. Although traditionally used in fixed-speed service, induction motors are increasingly being used with variable-frequency drives (VFDs) in variable-sp ...more...

Power inverter


An inverter on a free-standing solar plant Overview of solar-plant inverters A power inverter , or inverter , is an electronic device or circuitry that changes direct current (DC) to alternating current (AC). The input voltage , output voltage and frequency, and overall power handling depend on the design of the specific device or circuitry. The inverter does not produce any power; the power is provided by the DC source. A power inverter can be entirely electronic or may be a combination of mechanical effects (such as a rotary apparatus) and electronic circuitry. Static inverters do not use moving parts in the conversion process. Input and output Input voltage A typical power inverter device or circuit requires a relatively stable DC power source capable of supplying enough current for the intended power demands of the system. The input voltage depends on the design and purpose of the inverter. Examples include: 12 V DC, for smaller consumer and commercial inverters that typically run from a rechargeable 12 V ...more...

Member feedback about Power inverter:

Folder: car inverter


Power inverters can be very big and hefty—especially if they have built-in battery packs so they can work in a standalone way. They also generate lots of heat, which is why they have large heat sinks (metal fins) and often cooling fans as well. As you can see from our top photo, typical ones are about as big as a car battery or car battery charger; larger units look like a bit like a bank of car batteries in a vertical stack. The smallest inverters are more portable boxes the size of a car radio that you can plug into your cigarette lighter socket to produce AC for charging laptop computers or cellphones. Car Inverter Company is a leader among inverter manufacturer. Our main focus is creating the highest quality products. Car Inverter Company is an america inverter company located in Los Angeles. Our company concentrates on inverter design and inverter manufacture. The main products are car inverter, home inverter, pure sine wave inverter, 12v to 220v inverter and so on. The main function of an inverter is to convert direct current (DC) into alternating current (AC), and to change the voltage level into a stable 120 or 240 VAC that can be used by household appliances or "sold back" to the utility grid. The word "inverter" was originally used because the output wave form produced by its circuits alternates between a positive and a negative voltage. This device "inverts" the polarity of the power source (typically, a battery or PV array), causing the current to flow in alternating directions through the load. Hence the term "alternating current". A car inverter is an electrical device for converting 12-volt DC battery power into 120 volt AC power. Inverters are available in sizes ranging from as low as 30 watts up to 4,000 watts or more. For pratical purposes, an inverter size of 2,000-3,000 watts will be needed (or will already be installed) in an RV. There are two basic kinds of inverters:pure sine wave inverter and modified sine wave inverter. pure sine wave is what comes out of the wall. Modified sine wave is basically a square wave with the corners smoothed a little. Most stores only carry modified sine inverters because they are a lot cheaper. Operation of an inverter is, for the most part, automatic, although most require some settings to be programmed. When shore &/or generator power is lost, the inverter senses this and provides its own power to maintain an uninterupted power source. When shore power is restored or the generator started, the inverter will again sense this and, usually after a short delay, will automatically switch shore or generator power to the RV. Battery charging can also occur automatically, although it's usually possible to override this manually. There are two basic types of inverter available, known as modified sine-wave inverter and pure sine wave inverter, the former being the most common and least costly. Some appliances have been reported to not run on a modified sine-wave inverter, although the author has not experienced this with various inverters I've installed in RVs and boats. Our power inverter line has input voltages ranging from 12 volt dc power inverters, 24 volt dc power inverters and 48 volt dc power inverters. You will find a complete line of industrial grade power inverters, available in 12 volt, 24 volt and 48 volts. Our industrial power inverters are built tough and ready for use in commercial applications. We also offers 220 50hz export power inverters. The Export power inverters that we offer are modified sine 220 50hz power inverters, which are designed to be used in Africa and Europe. These 220 50hz power inverters are available in both 12 volt and 48 volt. Visit to learn more.

AC motor


An AC motor is an electric motor driven by an alternating current (AC). The AC motor commonly consists of two basic parts, an outside stator having coils supplied with alternating current to produce a rotating magnetic field, and an inside rotor attached to the output shaft producing a second rotating magnetic field. The rotor magnetic field may be produced by permanent magnets, reluctance saliency, or DC or AC electrical windings. Less common, AC linear motors operate on similar principles as rotating motors but have their stationary and moving parts arranged in a straight line configuration, producing linear motion instead of rotation. Operating principles The two main types of AC motors are induction motors and synchronous motors. The induction motor (or asynchronous motor) always relies on a small difference in speed between the stator rotating magnetic field and the rotor shaft speed called slip to induce rotor current in the rotor AC winding. As a result, the induction motor cannot produce torque near s ...more...

Electric motor


Various electric motors, compared with a 9 V battery. An electric motor is an electrical machine that converts electrical energy into mechanical energy . The reverse of this is the conversion of mechanical energy into electrical energy and is done by an electric generator , which has much in common with a motor. Most electric motors operate through the interaction between an electric motor's magnetic field and winding currents to generate force. In certain applications, such as in regenerative braking with traction motors in the transportation industry, electric motors can also be used in reverse as generators to convert mechanical energy into electric power. Found in applications as diverse as industrial fans, blowers and pumps, machine tools, household appliances, power tools, and disk drives, electric motors can be powered by direct current (DC) sources, such as from batteries, motor vehicles or rectifiers, or by alternating current (AC) sources, such as from the power grid, inverters or generators. Small ...more...

Brushless DC electric motor


Brushless DC electric motor ( BLDC motors , BL motors ) also known as electronically commutated motors (ECMs, EC motors), or synchronous DC motors , are synchronous motors powered by DC electricity via an inverter or switching power supply which produces an AC electric current to drive each phase of the motor via a closed loop controller . The controller provides pulses of current to the motor windings that control the speed and torque of the motor. The construction of a brushless motor system is typically similar to a permanent magnet synchronous motor (PMSM), but can also be a switched reluctance motor , or an induction (asynchronous) motor . The advantages of a brushless motor over brushed motors are high power to weight ratio, high speed, and electronic control. Brushless motors find applications in such places as computer peripherals (disk drives, printers), hand-held power tools, and vehicles ranging from model aircraft to automobiles. Brushless vs. brushed motors Brushed DC motors are a mature technolo ...more...

Nuclear power phase-out


A nuclear power phase-out is the discontinuation of usage of nuclear power for energy production. Often initiated because of concerns about nuclear power , phase-outs usually include shutting down nuclear power plants and looking towards fossil fuels and renewable energy . Three nuclear accidents have influenced the discontinuation of nuclear power: the 1979 Three Mile Island partial nuclear meltdown in the United States, the 1986 Chernobyl disaster in the USSR, and the 2011 Fukushima nuclear disaster in Japan. Following the March 2011 Fukushima nuclear disaster, Germany has permanently shut down eight of its 17 reactors and pledged to close the rest by the end of 2022. Italy voted overwhelmingly to keep their country non-nuclear. Switzerland and Spain have banned the construction of new reactors. Japan’s prime minister has called for a dramatic reduction in Japan’s reliance on nuclear power. Taiwan’s president did the same. Shinzō Abe , the new prime minister of Japan since December 2012, announced a pla ...more...

Mains electricity


Mains electricity is the general-purpose alternating-current (AC) electric power supply. Mains electricity is the form of electrical power that is delivered to homes and businesses, and it is the form of electrical power that consumers use when they plug kitchen appliances, televisions and electric lamps into wall sockets. The two principal properties of the electric power supply, voltage and frequency , differ between regions. A voltage of (nominally) 230 V and a frequency of 50 Hz is used in Europe, most of Africa, most of Asia, much of South America and Australia. In North America, the most common combination is 120 V and a frequency of 60 Hz. Other voltages exist, and some countries may have, for example, 230 V but 60 Hz. This is a concern to travelers, since portable appliances designed for one voltage and frequency combination may not operate with, or may even be destroyed by another. The use of different and incompatible plugs and sockets in different regions and countries provides some protection from ...more...

Hybrid vehicle drivetrain


Hybrid vehicle drivetrains transmit power to the driving wheels for hybrid vehicles . A hybrid vehicle has multiple forms of motive power. Hybrids come in many configurations. For example, a hybrid may receive its energy by burning petroleum, but switch between an electric motor and a combustion engine. Electrical vehicles have a long history combining internal combustion and electrical transmission –as in a diesel-electric powertrain–, although they have mostly been used for rail locomotives . A diesel-electric powertrain fails the definition of hybrid because the electrical drive transmission directly replaces the mechanical transmission rather than being a supplementary source of motive power. One of the earliest forms of hybrid land vehicle is the 'trackless' trolleybus of the 1930s, which normally used traction current delivered by wire. The trolleybus was commonly fitted with an internal combustion engine (ICE) either to directly power the bus or to independently generate electricity. This enabled the v ...more...

Polyphase system


One voltage cycle of a three-phase system A polyphase system is a means of distributing alternating-current electrical power . Polyphase systems have three or more energized electrical conductors carrying alternating currents with a defined phase angle between the voltage waves in each conductor; for three-phase voltage, the phase angle is 120° or ~2.09 radians. Polyphase systems are particularly useful for transmitting power to electric motors . The most common example is the three-phase power system used for industrial applications and for power transmission . A major advantage of three phase power transmission (using three conductors, as opposed to a single phase power transmission, which uses two conductors), is that, since the remaining conductors act as the return path for any single conductor, the power transmitted by a balanced three phase system is three times that of a single phase transmission but only one extra conductor is used. Thus, a 50% / 1.5x increase in the transmission costs achieves a 200 ...more...

Electrical grid


General layout of electricity networks. Voltages and depictions of electrical lines are typical for Germany and other European systems. An electrical grid is an interconnected network for delivering electricity from producers to consumers. It consists of generating stations that produce electrical power, high voltage transmission lines that carry power from distant sources to demand centers, and distribution lines that connect individual customers . Power stations may be located near a fuel source, at a dam site, or to take advantage of renewable energy sources, and are often located away from heavily populated areas. They are usually quite large to take advantage of economies of scale . The electric power which is generated is stepped up to a higher voltage at which it connects to the electric power transmission network. The bulk power transmission network will move the power long distances, sometimes across international boundaries, until it reaches its wholesale customer (usually the company that owns the ...more...

Wind power


Wind power stations in Xinjiang, China Global growth of installed capacity Wind power is the use of air flow through wind turbines to mechanically power generators for electric power . Wind power, as an alternative to burning fossil fuels , is plentiful, renewable , widely distributed, clean , produces no greenhouse gas emissions during operation, consumes no water, and uses little land. The net effects on the environment are far less problematic than those of nonrenewable power sources. Wind farms consist of many individual wind turbines which are connected to the electric power transmission network. Onshore wind is an inexpensive source of electric power, competitive with or in many places cheaper than coal or gas plants. Offshore wind is steadier and stronger than on land, and offshore farms have less visual impact, but construction and maintenance costs are considerably higher. Small onshore wind farms can feed some energy into the grid or provide electric power to isolated off-grid locations. Wind po ...more...

Charging station


An electric vehicle charging station , also called EV charging station , electric recharging point , charging point , charge point (not to be confused with the ChargePoint network) and EVSE (electric vehicle supply equipment), is an element in an infrastructure that supplies electric energy for the recharging of electric vehicles , such as plug-in electric vehicles , including electric cars , neighborhood electric vehicles and plug-in hybrids . As plug-in hybrid electric vehicles and battery electric vehicle ownership are expanding, there is a growing need for widely distributed publicly accessible charging stations (some of which support faster charging at higher voltages and currents than are available from residential EVSEs). Many charging stations are on-street facilities provided by electric utility companies or located at retail shopping centers and operated by many private companies. These charging stations provide one or a range of heavy duty or special connectors that conform to the variety of electr ...more...

Electric power industry


Electric power is transmitted on overhead lines like these, and also on underground high-voltage cables The electric power industry covers the generation , transmission , distribution and sale of electric power to the general public and industry. The generation of electricity started in 1882 when electricity was produced for electric lighting . In the 1880s and 1890s, growing economic and safety concerns lead to the regulation of the industry. Once an expensive novelty limited to the most densely populated areas, reliable and economical electric power has become an essential aspect for normal operation of all elements of developed economies. By the middle of the 20th century, electricity was seen as a " natural monopoly ", only efficient if a restricted number of organizations participated in the market; in some areas, vertically-integrated companies provide all stages from generation to retail, and only governmental supervision regulated the rate of return and cost structure. Since the 1990s, many regions ha ...more...

Service drop


In electric power distribution , a service drop is an overhead electrical line running from a utility pole , to a customer's building or other premises. It is the point where electric utilities provide power to their customers. The customer connection to an underground distribution system is usually called a "service lateral". Conductors of a service drop or lateral are usually owned and maintained by the utility company, but some industrial drops are installed and owned by the customer. At the customer's premises, the wires usually enter the building through a weatherhead that protects against entry of rain and snow, and drop down though conduit to an electric meter which measures and records the power used for billing purposes, then enters the main service panel . The utility's portion of the system ends, and the customer's wiring begins, at the output socket of the electric meter. The service panel will contain a "main" fuse or circuit breaker , which controls all of the electric current entering the buil ...more...

Distribution board


A distribution board (also known as panelboard , breaker panel , or electric panel ) is a component of an electricity supply system that divides an electrical power feed into subsidiary circuits , while providing a protective fuse or circuit breaker for each circuit in a common enclosure . Normally, a main switch , and in recent boards, one or more residual-current devices (RCD) or residual current breakers with overcurrent protection (RCBO), are also incorporated. In the United Kingdom, a distribution board designed for domestic installations is known as a consumer unit. North America An American circuit breaker panel featuring interchangeable circuit breakers North American distribution boards are typically housed in sheet metal enclosures, with the circuit breakers positioned in two columns operable from the front. Some panelboards are provided with a door covering the breaker switch handles, but all are constructed with a dead front; that is to say the front of the enclosure (whether it has a door or not) ...more...

Water and Power Development Authority


The Water and Power Development Authority (WAPDA) ( واٹر اینڈ پاور ڈیولپمنٹ اتھارٹی ) is a government -owned public utility maintaining power and water in Pakistan , although it does not manage thermal power . WAPDA includes Tarbela and Mangla dams among its resources. Its headquarters are in Lahore . History WAPDA was established by an act of parliament in 1958 to unify the maintenance of infrastructure previously overseen by provincial agencies. Its Chairmen included outstanding civil servants like Ghulam Ishaq Khan , Ghulam Faruque Khan and Aftab Ghulam Nabi Kazi who were subsequently President of Pakistan , Minister for Commerce and Economic Adviser, respectively. In October 2007, thermal power management was split into the newly formed Pakistan Electric Power Company (PEPCO). WAPDA Water vision 2025 WAPDA has formulated a comprehensive $25–33 billion National Water Resource and Hydropower Development Programme, entitled Water Vision 2025. The Water Vision 2025 projects are expected to generate 16,000 MW ...more...



Early 20th-century alternator made by Ganz Works in 1909 in Budapest , Hungary , in the power generating hall of the biggest hydroelectric station of the Russian Empire (photograph by Prokudin-Gorsky , 1911) An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current . For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature . Occasionally, a linear alternator or a rotating armature with a stationary magnetic field is used. In principle, any AC electrical generator can be called an alternator, but usually the term refers to small rotating machines driven by automotive and other internal combustion engines. An alternator that uses a permanent magnet for its magnetic field is called a magneto . Alternators in power stations driven by steam turbines are called turbo-alternators. Large 50 or 60 Hz three phase alternators in power plants generate most of the world's electric power, which is d ...more...

High-leg delta


High-leg delta (also known as wild-leg, stinger leg, bastard leg, high-leg, orange-leg, or red-leg delta) is a type of electrical service connection for three-phase electric power installations. It is used when both single and three-phase power is desired to be supplied from a three phase transformer (or transformer bank). The three-phase power is connected in the delta configuration, and the center point of one phase is grounded. This creates both a split-phase single phase supply (L1 or L2 to neutral on diagram at right) and three-phase (L1-L2-L3 at right). It is called "orange leg" because when it is connected per the NEC, the high leg is marked with orange "outer finish...or other effective means" (usually tape). By convention, the high leg is usually set in the center (B phase) lug in the involved panel, regardless of the L1-L2-L3 designation at the transformer. Supply Center-tapped delta transformer Center-tapped delta transformer voltages High-leg delta service is supplied in one of two ways. One is b ...more...

AC power plugs and sockets


AC power plugs and sockets are devices that allow electrically operated equipment to be connected to the primary alternating current (AC) power supply in a building. Electrical plugs and sockets differ in voltage and current rating, shape, size and type of connectors. The types used in each country are set by national standards, some of which are listed in the IEC technical report TR 60083, Plugs and socket-outlets for domestic and similar general use standardized in member countries of IEC. The scope of IEC TR 60083 states: "The report only contains systems for which standard sheets have been published in a National Standard, which may be a National Standard of the country itself or any other IEC member country". Plugs and sockets for portable appliances started becoming available in the 1880s, to replace connections to light sockets with easier to use wall-mounted outlets. A proliferation of types developed to address the issues of convenience and protection from electric shock. Today there are approximate ...more...



Pole-mounted distribution transformer with center-tapped secondary winding used to provide " split-phase " power for residential and light commercial service, which in North America is typically rated 120/240 V. A transformer is an electrical device that transfers electrical energy between two or more circuits through electromagnetic induction . A varying current in one coil of the transformer produces a varying magnetic field, which in turn induces a voltage in a second coil. Power can be transferred between the two coils through the magnetic field, without a metallic connection between the two circuits. Faraday's law of induction discovered in 1831 described this effect. Transformers are used to increase or decrease the alternating voltages in electric power applications. Since the invention of the first constant-potential transformer in 1885, transformers have become essential for the transmission , distribution , and utilization of alternating current electrical energy. A wide range of transformer design ...more...

Power dividers and directional couplers


A 3 dB 2.0–4.2 GHz power divider/combiner. Power dividers (also power splitters and, when used in reverse, power combiners ) and directional couplers are passive devices used mostly in the field of radio technology. They couple a defined amount of the electromagnetic power in a transmission line to a port enabling the signal to be used in another circuit. An essential feature of directional couplers is that they only couple power flowing in one direction. Power entering the output port is coupled to the isolated port but not to the coupled port. A directional coupler designed to split power equally between two ports is called a hybrid coupler . Directional couplers are most frequently constructed from two coupled transmission lines set close enough together such that energy passing through one is coupled to the other. This technique is favoured at the microwave frequencies where transmission line designs are commonly used to implement many circuit elements. However, lumped component devices are also possible ...more...

Hybrid vehicle


A hybrid vehicle uses two or more distinct types of power, such as internal combustion engine to drive an electric generator that powers an electric motor , e.g. in diesel-electric trains using diesel engines to drive an electric generator that powers an electric motor, and submarines that use diesels when surfaced and batteries when submerged. Other means to store energy include pressurized fluid in hydraulic hybrids . Power Power sources for hybrid vehicles include: Coal , wood or other solid combustibles Compressed or liquefied natural gas Petrol (gasoline) or Diesel fuel Human powered e.g. pedaling or rowing Electromagnetic fields , Radio waves Electric batteries / capacitors Overhead electricity Hydraulic accumulator Hydrogen Flywheel Solar Wind Vehicle type A biodiesel hybrid bus in Montreal, Canada Two-wheeled and cycle-type vehicles Mopeds , electric bicycles , and even electric kick scooters are a simple form of a hybrid, powered by an internal combustion engine or electric motor and the rider's mus ...more...

Electric car


Electric cars charging on street in Rome in 2016. An electric car is an automobile that is propelled by one or more electric motors , using energy stored in rechargeable batteries . The first practical electric cars were produced in the 1880s. Electric cars were popular in the late 19th century and early 20th century, until advances in internal combustion engines, electric starters in particular, and mass production of cheaper gasoline vehicles led to a decline in the use of electric drive vehicles . In 1897, electric cars found their first commercial use in the USA. New York City taxis were electric, and they were manufactured by the Philadelphian Electric Carriage and Wagon company. During the 20th century, the main manufacturers of electric vehicles in the US were Anthony Electric, Baker , Columbia, Anderson, Edison, Riker, Milburn and others. Unlike gasoline-powered vehicles, the electric ones were quieter and did not require gear changes. Since 2008, a renaissance in electric vehicle manufacturing occu ...more...

Electricity meter


North American domestic analog electricity meter. Electricity meter with transparent plastic case (Israel). North American domestic digital electricity meter. An electricity meter , electric meter , electrical meter , or energy meter is a device that measures the amount of electric energy consumed by a residence , a business , or an electrically powered device. Electric utilities use electric meters installed at customers' premises to measure electric energy delivered to their customers for billing purposes. They are typically calibrated in billing units, the most common one being the kilowatt hour [kWh]. They are usually read once each billing period. When energy savings during certain periods are desired, some meters may measure demand, the maximum use of power in some interval. "Time of day" metering allows electric rates to be changed during a day, to record usage during peak high-cost periods and off-peak, lower-cost, periods. Also, in some areas meters have relays for demand response load shedding durin ...more...

Amtrak's 60 Hz traction power system


Amtrak operates a 60 Hz Traction power system along the Northeast Corridor between New Haven, Connecticut and Boston, Massachusetts . This system was built in the late 1990s and supplies locomotives with power from an overhead catenary system at 25 kV, 60 Hz. The system is also commonly known as the Northend Electrification, in contrast to the Southend Electrification that runs from New York City to Washington DC. History In 1992, Congress passed the Amtrak Authorization and Development Act requiring Amtrak to establish high-speed rail passenger service between New York City and Boston. The goal was to reduce travel time in this corridor from 4.5 hours to less than 3 hours. Revenue from this service was expected to play a critical role in helping Amtrak achieve operating self-sufficiency by 2003. Before Amtrak can begin high-speed rail service, 155 miles of rail line between New Haven and Boston had to be electrified. Previously, electrified Metroliner service was available between Washington, D.C. and New Ha ...more...

Electric vehicle


An electric vehicle , also called an electric drive vehicle , uses one or more electric motors or traction motors for propulsion. An electric vehicle may be powered through a collector system by electricity from off-vehicle sources, or may be self-contained with a battery, solar panels or an electric generator to convert fuel to electricity. EVs include road and rail vehicles, surface and underwater vessels, electric aircraft and electric spacecraft . EVs first came into existence in the mid-19th century, when electricity was among the preferred methods for motor vehicle propulsion, providing a level of comfort and ease of operation that could not be achieved by the gasoline cars of the time. Modern internal combustion engines have been the dominant propulsion method for motor vehicles for almost 100 years, but electric power has remained commonplace in other vehicle types, such as trains and smaller vehicles of all types. In the 21st century, EVs saw a resurgence due to technological developments and an inc ...more...



"Dynamo Electric Machine" (end view, partly section, U.S. Patent 284,110 ) A dynamo is an electrical generator that produces direct current with the use of a commutator . Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor , the alternating-current alternator , and the rotary converter . Today, the simpler alternator dominates large scale power generation, for efficiency, reliability and cost reasons. A dynamo has the disadvantages of a mechanical commutator. Also, converting alternating to direct current using power rectification devices (vacuum tube or more recently solid state ) is effective and usually economical. Etymology The word dynamo (from the Greek word dynamis(δύναμις), meaning force or power) was originally another name for an electrical generator , and still has some regional usage as a replacement for the word generator. The word "dynamo" w ...more...

Dabhol Power Station


Also see Dabhol Power Company and Enron Scandal Dabhol Power Station is located near Anjanwel village in Ratnagiri district in Maharashtra , India , about 160 kilometres (99 mi) south of Mumbai . The power station was a built by the Dabhol Power Company (DPC), which was a joint venture of Enron , General Electric , Bechtel and Maharashtra Power Development Corporation. At the start of its construction in 1992, the Dabhol power station was the biggest foreign investment in India. The plant was mired in controversies of corruption and malpractices involving Enron and people at the highest political levels of the Indian and the United States ( Clinton and Bush Administration ) governments. History Construction of the Dabhol Power Station was planned to be completed in two phases. The first phase was a 740 MW unit to use naphtha as the fuel. Construction started in 1992 and finally completed in May 1999. The next phase was 1700 MW of units using liquefied natural gas (LNG) as fuel. At its height, the constructi ...more...

Industrial and multiphase power plugs and sockets


Industrial and multiphase plugs and sockets provide a connection to the electrical mains rated at higher voltages and currents than household plugs and sockets. They are generally used in polyphase systems , with high currents, or when protection from environmental hazards is required. Industrial outlets may have weatherproof covers, waterproofing sleeves, or may be interlocked with a switch to prevent accidental disconnection of an energized plug. Some types of connectors are approved for hazardous areas such as coal mines or petrochemical plants, where flammable gas may be present. Almost all three-phase power plugs have an earth (ground) connection, but may not have a neutral because three-phase loads such as motors do not need the neutral. Such plugs have only four prongs (earth, and the three phases). An example of a socket with neutral is the L21-30 (30 A) and the L21-20 (20 A) both of which have five pins (earth, neutral, and X, Y, Z phases). While some forms of power plugs and sockets are set by inter ...more...

SAE J1772


SAE J1772 ( IEC Type 1) is a North American standard for electrical connectors for electric vehicles maintained by the SAE International and has the formal title "SAE Surface Vehicle Recommended Practice J1772, SAE Electric Vehicle Conductive Charge Coupler". It covers the general physical, electrical, communication protocol, and performance requirements for the electric vehicle conductive charge system and coupler. The intent is to define a common electric vehicle conductive charging system architecture including operational requirements and the functional and dimensional requirements for the vehicle inlet and mating connector. History The older Avcon connector, featured here on a Ford Ranger EV The main stimulus for the development of SAE J1772 came from the California Air Resources Board. Formerly electric vehicles like the General Motors EV1 had used inductive charger couplers. These were ruled out in favor of conductive coupling to supply electricity for recharging with the California Air Resources Boar ...more...

E-plane and H-plane


The E-plane and H-plane are reference planes for linearly polarized waveguides , antennas and other microwave devices. In waveguide systems, as in the electric circuits, it is often desirable to be able to split the circuit power into two or more fractions. In a waveguide system, an element called a junction is used for power division. In a low frequency electrical network, it is possible to combine circuit elements in series or in parallel , thereby dividing the source power among several circuit components. In microwave circuits, a waveguide with three independent ports is called a TEE junction. The output of E-Plane Tee is 180° out of phase where the output of H-plane Tee is in phase. E-Plane For a linearly-polarized antenna, this is the plane containing the electric field vector (sometimes called the E aperture) and the direction of maximum radiation. The electric field or "E" plane determines the polarization or orientation of the radio wave. For a vertically polarized antenna, the E-plane usually coinci ...more...

Centrifugal switch


A centrifugal switch is an electric switch that operates using the centrifugal force created from a rotating shaft, most commonly that of an electric motor or gasoline engine . The switch is designed to activate or de-activate as a function of the rotational speed of the shaft. Perhaps the most common use of centrifugal switches is within single-phase , split-phase induction motors . Here, the switch is used to disconnect the starting winding of the motor once the motor approaches its normal operating speed. In this case, the centrifugal switch consists of weights mounted to the shaft of the motor and held near the shaft by spring force. At rest, levers attached to the weights press a low-friction , non-conductive plate against a set of electrical contacts mounted to the motor housing, closing the contacts and connecting the starting winding to the power source. When the motor approaches its normal operating speed, centrifugal force overcomes the spring force and the weights swing out, raising the plate away ...more...

Distribution transformer


A distribution transformer or service transformer is a transformer that provides the final voltage transformation in the electric power distribution system, stepping down the voltage used in the distribution lines to the level used by the customer. The invention of a practical efficient transformer made AC power distribution feasible; a system using distribution transformers was demonstrated as early as 1882. If mounted on a utility pole , they are called pole-mount transformers . If the distribution lines are located at ground level or underground, distribution transformers are mounted on concrete pads and locked in steel cases, thus known as pad-mount transformers . Distribution transformers normally have ratings less than 200 kVA , although some national standards can allow for units up to 5000 kVA to be described as distribution transformers. Since distribution transformers are energized for 24 hours a day (even when they don't carry any load), reducing iron losses has an important role in their design. ...more...

IEC 60309


Two IEC-60309-style plugs inserted into wall-mounted sockets IEC 60309 (formerly IEC 309 and CEE 17 , also published by CENELEC as EN 60309 ) is an international standard from the International Electrotechnical Commission (IEC) for "plugs, socket-outlets and couplers for industrial purposes". The maximum voltage allowed by the standard is 1000  V DC or AC ; the maximum current , 800  A ; and the maximum frequency , 500  Hz . The ambient temperature range is −25 °C to 40 °C . There is a range of plugs and sockets of different sizes with differing numbers of pins, depending on the current supplied and number of phases accommodated. The fittings are popular in open-air conditions, as they include IP44 weather-proofing. They are also sometimes used in situations where their special capabilities (such as high current rating or three-phase facilities) are not needed, to discourage potential users from connecting domestic appliances to the sockets, as 'normal' domestic plugs will not fit. The cable connectors and so ...more...

Ground and neutral


As the neutral point of an electrical supply system is often connected to earth ground , ground and neutral are closely related. Under certain conditions, a conductor used to connect to a system neutral is also used for grounding (earthing) of equipment and structures. Current carried on a grounding conductor can result in objectionable or dangerous voltages appearing on equipment enclosures , so the installation of grounding conductors and neutral conductors is carefully defined in electrical regulations. Where a neutral conductor is used also to connect equipment enclosures to earth, care must be taken that the neutral conductor never rises to a high voltage with respect to local ground. Definitions Ground or earth in a mains ( AC power) electrical wiring system is a conductor that provides a low- impedance path to the earth to prevent hazardous voltages from appearing on equipment (high voltage spikes). (The terms "ground" and "earth" are used synonymously here. "Ground" is more common in North American En ...more...

Electrical wiring


Electrical symbols for wiring Electrical wiring is an electrical installation of cabling and associated devices such as switches, distribution boards, sockets and light fittings in a structure. Wiring is subject to safety standards for design and installation. Allowable wire and cable types and sizes are specified according to the circuit operating voltage and electric current capability, with further restrictions on the environmental conditions, such as ambient temperature range, moisture levels, and exposure to sunlight and chemicals. Associated circuit protection, control and distribution devices within a building's wiring system are subject to voltage, current and functional specification. Wiring safety codes vary by locality, country or region. The International Electrotechnical Commission (IEC) is attempting to harmonise wiring standards amongst member countries, but significant variations in design and installation requirements still exist. Wiring codes of practice and regulations Wiring layout plan fo ...more...

Air conditioning


Air conditioning units outside a building. Air conditioning (often referred to as AC, A/C, or air con ) is the process of removing heat from the interior of an occupied space, to improve the comfort of occupants. Air conditioning can be used in both domestic and commercial environments. This process is most commonly used to achieve a more comfortable interior environment, typically for humans or animals; however, air conditioning is also used to cool/dehumidify rooms filled with heat-producing electronic devices, such as computer servers , power amplifiers , and even to display and store artwork. Air conditioners often use a fan to distribute the conditioned air to an occupied space such as a building or a car to improve thermal comfort and indoor air quality . Electric refrigerant-based AC units range from small units that can cool a small bedroom, which can be carried by a single adult, to massive units installed on the roof of office towers that can cool an entire building. The cooling is typically achieve ...more...

Doherty amplifier


The Doherty amplifier is a modified class B radio frequency amplifier invented by William H. Doherty of Bell Telephone Laboratories Inc in 1936. In Doherty's day, within the Western Electric product line, the eponymous electronic device was operated as a linear amplifier with a driver which was modulated. In the 50,000 watt implementation, the driver was a complete 5,000 watt transmitter which could, if necessary, be operated independently of the Doherty amplifier and the Doherty amplifier was used to raise the 5,000 watt level to the required 50,000 watt level. The amplifier was usually configured as a grounded-cathode, carrier-peak amplifier using two vacuum tubes in parallel connection, one as a class B carrier tube and the other as a class B peak tube ( power transistors in modern implementations). The tubes' source (driver) and load (antenna) were split and combined through + and – 90 degree phase shifting networks. Alternate configurations included a grounded-grid carrier tube and a grounded-cathode pe ...more...

Residual-current device


A residual-current device ( RCD ), or residual-current circuit breaker ( RCCB ), is a device that instantly breaks an electric circuit to prevent serious harm from an ongoing electric shock. Injury may still occur in some cases, for example if a human falls after receiving a shock. In the United States and Canada , the device is more commonly known as a ground fault circuit interrupter ( GFCI ), ground fault interrupter ( GFI ) or an appliance leakage current interrupter ( ALCI ). In the United Kingdom , these are better known by their initials RCD , and a combined RCD+MCB ( miniature circuit breaker ) is known as a RCBO ( residual-current circuit breaker with overcurrent protection ). In Australia , they are sometimes known as safety switches or an RCD . An earth leakage circuit breaker (ELCB) may be a residual-current device, although an older type of voltage-operated earth leakage circuit breaker also exists. These electrical wiring devices are designed to quickly and automatically disconnect a circuit whe ...more...

Transformer types


Circuit symbols Transformer with two windings and iron core. Transformer with three windings. The dots show the relative configuration of the windings. Transformer with electrostatic screen preventing capacitive coupling between the windings. An electric arc furnace the transformer has heavy copper bus for the low voltage winding, which can be rated for tens of thousands of amperes. They are immersed in oil for cooling and insulation, and are designed to survive frequent short circuits. A variety of types of electrical transformer are made for different purposes. Despite their design differences, the various types employ the same basic principle as discovered in 1831 by Michael Faraday , and share several key functional parts. Power transformers Laminated core Laminated core transformer This is the most common type of transformer, widely used in electric power transmission and appliances to convert mains voltage to low voltage to power electronic devices. They are available in power ratings ranging from mW to ...more...

Phasor measurement unit


A phasor measurement unit (PMU) is a device which measures the electrical waves on an electricity grid using a common time source for synchronization. Time synchronization allows synchronized real-time measurements of multiple remote measurement points on the grid. The resulting measurement is known as a synchrophasor . PMUs are considered to be one of the most important measuring devices in the future of power systems. A PMU can be a dedicated device, or the PMU function can be incorporated into a protective relay or other device. History In 1893, Charles Proteus Steinmetz presented a paper on simplified mathematical description of the waveforms of alternating current electricity. Steinmetz called his representation a phasor . With the invention of phasor measurement units (PMU) in 1988 by Dr. Arun G. Phadke and Dr. James S. Thorp at Virginia Tech, Steinmetz’s technique of phasor calculation evolved into the calculation of real time phasor measurements that are synchronized to an absolute time reference pr ...more...

15 kV AC railway electrification


A pylon of a single phase AC 110 kV -powerline near Bartholomä in Germany. Lines of these type are used in Germany to supply electric railways with single phase AC at 16.7 hertz . In the substations of the railway, transformers are used to step it down to 15 kV . The 15 kV, 16.7 Hz AC railway electrification system is used in Germany , Austria , Switzerland , Sweden and Norway . The high voltage enables high power transmission with the lower frequency reducing the losses of the traction motors that were available at the beginning of the 20th century. Railway electrification in late 20th century tends to use 25 kV, 50 Hz AC systems which has become the preferred standard for new railway electrifications but extensions of the existing 15 kV networks are not completely unlikely. In particular, the Gotthard Base Tunnel (opened on 1 June 2016) still uses 15 kV, 16.7 Hz electrification. Due to high conversion costs, it is unlikely that existing 15 kV, 16.7 Hz systems will be converted to 25 kV, 50 Hz despite the fa ...more...

Earthing system


In an electrical installation an earthing system or grounding system connects specific parts of that installation with the Earth's conductive surface for safety and functional purposes. The point of reference is the Earth's conductive surface. The choice of earthing system can affect the safety and electromagnetic compatibility of the installation. Regulations for earthing systems vary considerably among countries, though many follow the recommendations of the International Electrotechnical Commission . Regulations may identify special cases for earthing in mines, in patient care areas, or in hazardous areas of industrial plants. In addition to electric power systems, other systems may require grounding for safety or function. Tall structures may have lightning rods as part of a system to protect them from lightning strikes. Telegraph lines may use the Earth as one conductor of a circuit, saving the cost of installation of a return wire over a long circuit. Radio antennas may require particular grounding for ...more...

Commutator (electric)


Commutator in a universal motor from a vacuum cleaner. Parts: (A) commutator, (B) brush, (C) rotor ( armature ) windings, (D) stator (F) (field) windings, (E) brush guides A commutator is a rotary electrical switch in certain types of electric motors and electrical generators that periodically reverses the current direction between the rotor and the external circuit. It consists of a cylinder composed of multiple metal contact segments on the rotating armature of the machine. Two or more electrical contacts called " brushes " made of a soft conductive material like carbon press against the commutator, making sliding contact with successive segments of the commutator as it rotates. The windings (coils of wire) on the armature are connected to the commutator segments. Commutators are used in direct current (DC) machines: dynamos (DC generators) and many DC motors as well as universal motors . In a motor the commutator applies electric current to the windings. By reversing the current direction in the rotating w ...more...

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