The waveform of 230 volt, 50 Hz compared with 110 V, 60 Hz.

The utility frequency (American English) or mains frequency (British English) is the frequency at which alternating current (AC) is transmitted from a power plant to the end user. In most parts of the Americas, it is typically 60 Hz, and in most parts of the rest of the world it is typically 50 Hz. Precise details are shown in the list of countries with mains power plugs, voltages and frequencies. Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... For other uses, see American English (disambiguation). ... British English (BrE, en-GB) is a broad term used to distinguish the forms of the English language used in the United Kingdom from forms used elsewhere. ... FreQuency is a music video game developed by Harmonix and published by SCEI. It was released in November 2001. ... City lights viewed in a motion blurred exposure. ... A power station (also power plant) is a facility for the generation of electric power. ... Economics and commerce define an end-user as the person who uses a product. ... World map showing the Americas CIA political map of the Americas The Americas are the lands of the Western hemisphere or New World consisting of the continents of North America[1] and South America with their associated islands and regions. ... The hertz (symbol: Hz) is the SI unit of frequency. ... The terms line voltage/frequency or mains voltage/frequency commonly refer to the electrical voltage and frequency used in the low voltage parts (in particular wall sockets) of an alternating current electricity supply network. ...

Places that now use the 50 Hz frequency tend to use 230 V, and those that now use 60 Hz tend to use 117 V. International safety symbol Caution, risk of electric shock (ISO 3864), colloquially known as high voltage symbol. ...

Unless specified by the manufacturer to operate on either 50 or 60 Hz, appliances may not operate efficiently or even safely if used on other than the intended supply frequency.

History

Operating factors

Several factors influence the choice of frequency in an AC system. Lighting, motors, transformers, generators and transmission lines all have characteristics which depend on the power frequency.

The first applications of commercial electric power were incandescent lighting and commutator-type electric motors. Both devices operate well on DC, but DC cannot be easily transmitted long distances at utilization voltage and also cannot be easily changed in voltage. In mathematics, the commutator gives an indication of the extent to which a certain binary operation fails to be commutative. ...

With AC, transformers can be used to step down high transmission voltages to lower utilization voltage. Since, for a given power level, the dimensions of a transformer are roughly inversely proportional to frequency, a system with many transformers would be more economical at a higher frequency.

If an incandescent lamp is operated off a low-frequency current, the filament cools on each half-cycle of the alternating current, leading to perceptible change in brightness and flicker of the lamps; the effect is more pronounced with arc lamps, and the later mercury-vapor and fluorescent lamps.

Commutator-type motors do not operate well on high-frequency AC since the rapid changes of current are opposed by the inductance of the motor field; even today, although commutator-type universal motors are common in household appliances, they are universally of low ratings less than 1 kW. Once the induction motor had been developed, it was found to work well on frequencies around 50 to 60 Hz but with the materials available in the late 1800s would not work well at a frequency of, say, 133 Hz. There is a fixed relationship between the number of magnetic poles in the induction motor field, the frequency of the alternating current, and the rotation speed; so, a given standard speed limits the choice of frequency (and the reverse).

Electric power transmission over long lines favors lower frequencies. The effects of the distributed capacitance and inductance of the line are less at low frequency. Power line redirects here. ...

Generators operated by slow-speed engines will produce lower frequencies, for a given number of poles, than those operated by, for example, a high-speed steam turbine. For very slow prime mover speeds, it would be costly to build a generator with enough poles to provide a high AC frequency. As well, synchronizing two generators to the same speed was found to be easier at lower speeds. A Siemens steam turbine with the case opened. ...

Generators can only be interconnected to operate in parallel if they are of the same frequency and wave-shape. By standardizing the frequency used, generators in a geographic area can be interconnected, providing reliability and cost savings.

Direct-current power was not entirely displaced by alternating current and was useful in railway and electrochemical processes. Prior to the development of mercury arc valve rectifiers, rotary converters were used to produce DC power from AC. Like other commutator-type machines, these worked better with lower frequencies. A mercury arc valve (mercury vapor rectifier) is a type of electrical rectifier which converts alternating current into direct current. ... AC, half-wave and full wave rectified signals A rectifier is an electrical device, comprising one or more semiconductive devices (such as diodes) or vacuum tubes arranged for converting alternating current to direct current. ...

All of these factors interact and make selection of a power frequency a matter of considerable importance. The best frequency is a compromise between contradictory requirements.

Development

Very early isolated AC generating schemes used arbitrary frequencies based on convenience for steam engine, water turbine and electrical generator design. In the late 19th century, designers would pick a relatively high frequency for systems featuring transformers and arc lights, so as to economize on transformer materials, but would pick a lower frequency for systems with long transmission lines or feeding primarily motor loads or rotary converters for producing direct current. Frequencies between 16 2/3 Hz and 133 1/3 Hz were used on different systems. For example, the city of Coventry, England, in 1895 had a unique 87 Hz single-phase distribution system that was in use until 1906. // The term steam engine may also refer to an entire railroad steam locomotive. ... Kaplan turbine and electrical generator cut-away view. ... “Dynamo” redirects here. ... Three-phase pole-mounted step-down transformer. ... Rotary Converter refers to a class of electrical machinery that was used to convert one form of electrical power into another form. ... Direct current (DC or continuous current) is the continuous flow of electricity through a conductor such as a wire from high to low potential. ...

Once induction motors became common, it was important to standardize frequency for compatibility with the customer's equipment. Standardizing on one frequency also, later, allowed interconnection of generating plants on a grid for economy and security of operation. Electric motors of various sizes. ... Power transmission is the movement of energy from its place of generation to a location where it is applied to performing useful work. ...

Though many theories exist, and quite a few entertaining urban legends, there is little certitude in the details of the history of 60 Hz vs. 50 Hz. What is known is that Westinghouse in the US decided on 60 Hz and AEG in Germany decided on 50 Hz, eventually leading to the world being mostly divided into two frequency camps. Frequencies much below 50 Hz gave noticeable flicker of arc or incandescent lighting. Westinghouse decided on 60 Hz before 1892 and AEG decided on 50 Hz by 1899. Tesla is believed to have had a key influence in the choice of 60 Hz by Westinghouse. Use of 60 Hz allowed induction motors to operate at the same speeds as standardized steam engines common in the late 19th century. The Westinghouse Electric Corporation was an organization founded by George Westinghouse in 1886 as Westinghouse Electric & Manufacturing Company. ... AEG volt-metre designed by Peter Behrens AEG (Allgemeine Elektrizitäts-Gesellschaft) (English Translation: General Electricity Company) was a German producer of electronics and electrical equipment. ...

However, the first generators at the Niagara Falls project, built by Westinghouse, were 25 Hz because the turbine speed had already been selected before alternating current power transmission had been definitively selected. City lights viewed in a motion blurred exposure. ...

Westinghouse would have selected a low frequency of 30 Hz to drive motor loads, but the turbines for the project had already been specified at a speed which was incompatible with a generator designed for 30 Hz. Because the Niagara project was so influential on electric power systems design, 25 Hz prevailed as the North American standard for low-frequency AC. A Westinghouse study concluded that 40 Hz would have been a good compromise between lighting, motor, and transmission needs. Although frequencies near 40 Hz found some commercial use, this frequency never overcame the "installed base" of 25 Hz, 50 Hz and 60 Hz equipment. The oldest continuously-operating commercial hydroelectric power plant in the United States, at Mechanicville, New York, still produces electric power at 40 Hz and supplies power to the local 60 Hz transmission system through frequency changers. Hydroelectricity is the worlds most important renewable energy source The Nagarjuna dam & hydro-electric plant, India Hydroelectricity is electricity produced by hydropower. ... A frequency changer or frequency converter is an electronic device that converts alternating current (AC) of one frequency to alternating current of another frequency. ...

Frequency changers used to convert between 25 Hz and 60 Hz systems were awkward to design; a 60 Hz machine with 24 poles would turn at the same speed as a 25 Hz machine with 10 poles, making the machines large, slow-speed and expensive. A ratio of 60/30 would have simplified these designs, but the installed base at 25 Hz was too large to be economically opposed.

AEG's choice of 50 Hz is thought by some to relate to a more "metric-friendly" number than 60. It may also have been an intentional decision to be incompatible, although since so many frequencies were used it may not have been clear that any one value was desirable. A plethora of frequencies continued in broad use (London in 1918 had 10 different frequencies), and it wasn't until after World War II with the advent of affordable electrical consumer goods that broader standards were enacted. Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki Tōjō Casualties Military dead: 17,000,000 Civilian dead: 33,000...

Other frequencies were somewhat common in the first half of the 20th century, and remain in use in isolated cases today, often tied to the 60 Hz system via a rotary converter or static inverter frequency changer. Because of the cost of conversion, some parts of the distribution system may continue to operate on original frequencies even after a new frequency is chosen. 25 Hz power was used in Ontario, Quebec, the northern USA, and for railway electrification. In the 1950s, many 25 Hz systems, from the generators right through to household appliances, were converted and standardized. Some 25 Hz generators still exist at the Beck 1 and Rankine generating stations near Niagara Falls to provide power for large industrial customers who did not want to replace existing equipment; and some 25 Hz motors exist in New Orleans' floodwater pumps [1]. Rotary Converter refers to a class of electrical machinery that was used to convert one form of electrical power into another form. ... A static inverter station is the terminal equipment for a high voltage direct current transmission line, in which direct current is converted to three-phase alternating current, and, usually, the reverse. ... Motto: Ut Incepit Fidelis Sic Permanet (Latin: Loyal she began, loyal she remains) Capital Toronto Largest city Toronto Official languages English Government - Lieutenant-Governor James K. Bartleman - Premier Dalton McGuinty (Liberal) Federal representation in Canadian Parliament - House seats 106 - Senate seats 24 Confederation July 1, 1867 (1st) Area [1] Ranked... Motto: Je me souviens (French: I remember) Capital Quebec City Largest city Montreal Official languages French Government - Lieutenant-Governor Lise Thibault - Premier Jean Charest (PLQ) Federal representation in Canadian Parliament - House seats 75 - Senate seats 24 Confederation July 1, 1867 (1st) Area Ranked 2nd - Total 1,542,056 km² - Water... Overhead wire in Coventry, England A railway electrification system is a way of supplying electric power to electric locomotives or multiple units. ... There are very few or no other articles that link to this one. ... For other uses, see Niagara Falls (disambiguation). ...

In the United States, the Southern California Edison company had standardized on 50 Hz and did not completely change frequency of their generators and customer equipment to 60 Hz until around 1948.

Utility Frequencies in Use in 1897 in North America

Even by the middle of the 20th century, utility frequencies were still not entirely standardized at the now-common 50 Hz or 60 Hz. In 1946, a reference manual for designers of radio equipment listed the following now obsolete frequencies as in use. Many of these regions also had 50 cycle, 60 cycle or direct current supplies. 1897 (MDCCCXCVII) was a common year starting on Friday (see link for calendar). ...

Frequencies in Use in 1946 (As well as 50 Hz and 60 Hz)

Where regions are marked (*), this is the only utility frequency shown for that region.

Railways

Other utility frequencies are used. Germany, Austria, and Switzerland use traction power networks for railways, distributing single-phase AC at 16 2/3 Hz. A frequency of 25 Hz was used for the Austrian railway Mariazeller Bahn and some railway systems in New York and Pennsylvania (Amtrak) in the USA. Other railway systems are energized at the local commercial power frequency, 50 Hz or 60 Hz. Traction power may be derived from commercial power supplies by frequency converters, or in some cases may be produced by dedicated generating stations. A traction power network is an electricity grid for the supply of electric trains. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Acela Express in West Windsor, NJ Amtrak Cascades service with tilting Talgo trainsets in Seattle, Washington Amtrak train in downtown Orlando, Florida For other uses, see Amtrak (disambiguation). ...

400Hz

Frequencies as high as 400 Hz are used in aerospace and some special-purpose computer power supplies and hand-held machine tools. Such high frequencies cannot be economically transmitted long distances, so 400 Hz power systems are usually confined to a building or vehicle. Transformers and motors for 400Hz are much smaller and lighter than at 50 or 60 Hz, which is an advantage in aircraft and ships. The top cover has been removed to show the internals of a computer Power supply Unit. ...

Stability

The frequency of large interconnected power distribution systems is tightly regulated so that, over the course of a day, the average frequency is maintained at the nominal value within a few hundred parts per million. While this allows simple electric clocks, based on synchronous electric motors, to keep accurate time, the primary reason for accurate frequency control is to allow the flow of alternating current power from multiple generators through the network to be controlled. Rotating magnetic field as a sum of magnetic vectors from 3 phase coils An electric motor converts electrical energy into mechanical energy. ...

Frequency of the system will vary as load is added to the system or as generators are shut down; other generators are adjusted in speed so that the average system frequency stays nearly constant. During a severe overload caused by failure of generators or transmission lines, the power system frequency will decline. Loss of an interconnection carrying a large amount of power (relative to system total generation) will cause system frequency to rise. Special protection relays in the power system network sense the decline and may automatically initiate load shedding or tripping of interconnection lines, to preserve the operation of at least part of the network. Quite small frequency deviations, say 0.5 Hz on a 50 Hz or 60 Hz network, will result in automatic load shedding or other control actions to restore system frequency. Smaller power systems, not extensively interconnected with many generators and loads, may not maintain frequency with the same degree of accuracy.

Audible noise and interference

AC-powered appliances can give off a characteristic hum (often referred to as the "60 cycle hum" or "mains hum"), at the multiples of the frequencies of AC power that they use. This often occurs in poorly made speakers. Most countries have chosen their television standard to approximate their mains supply frequency. This helps prevent powerline hum and magnetic interference from causing visible beat frequencies in the displayed picture. A hum is a sound with a particular timbre (or sound quality), usually a monotone or with slightly varying tones, often produced by machinery in operation or by insects in flight. ... Spectrum of mains hum at 60 Hz Electric hum, mains hum, or power line hum is an audible oscillation at the frequency of the mains alternating current, which is usually 50 or 60 hertz depending on the local electric utility configuration (see Mains electricity). ... A loudspeaker is a device which converts an electrical signal into sound. ...

See also

• Mains
• List of countries with mains power plugs, voltages and frequencies
• Power connector

Mains may mean or refer to, or be a subject of: Mains electricity Electricity transmission Public utility, about mains services, including electricity, natural gas, water, and sewage disposal Mains (Scotland), about the central steading of a townland BMX racing See also: Main Mane Category: ... The terms line voltage/frequency or mains voltage/frequency commonly refer to the electrical voltage and frequency used in the low voltage parts (in particular wall sockets) of an alternating current electricity supply network. ... A power connector is an electrical connector designed to carry a significant amount of electrical power, usually as DC or low-frequency AC. Some types of RF connector may also carry large amounts of power, but are considered as a separate category. ...

Further reading

• Owen, E.L, The Origins of 60-Hz as a Power Frequency, Industry Applications Magazine, IEEE, Volume: 3, Issue 6, Nov.-Dec. 1997, Pages 8, 10, 12-14.
• Furfari, F.A., The Evolution of Power-Line Frequencies 133 1/3 to 25 Hz, Industry Applications Magazine, IEEE, Sep/Oct 2000, Volume 6, Issue 5, Pages 12-14, ISSN 1077-2618.
• Rushmore, D.B., Frequency, AIEE Transactions, Volume 31, 1912, pages 955-983, and discussion on pages 974-978.
• Blalock, Thomas J., Electrification of a Major Steel Mill - Part II Development of the 25 Hz System, Industry Applications Magazine, IEEE, Sep/Oct 2005, Pages 9-12, ISSN 1077-2618.

References

• Edwin J. Houston and Arthur Kennelly, Recent Types of Dynamo-Electric Machinery, copyright American Technical Book Company 1897, published by P.F. Collier and Sons New York, 1902
• Central Station Engineers of the Westinghouse Electric Corporation, Electrical Transmission and Distribution Reference Book, 4th Ed., Westinghouse Electric Corporation, East Pittsburgh PA, 1950, no ISBN
• Donald G. Fink and H. Wayne Beaty, Standard Handbook for Electrical Engineers, Eleventh Edition,McGraw-Hill, New York, 1978, ISBN 0-07-020974-X
• H.T. Kohlhaas,(ed.), Reference Data for Radio Engineers 2nd Edition, Federal Telephone and Radio Corporation, New York, 1946, no ISBN