why 50Hz power supply is standard in all countries...?
- BrambleLv 71 decade agoFavourite answer
The reason is that this is in the optimum range for power supply on a national scale. The use of lower frequencies would cause the size, weight and cost of the installed equipment to increase and the flicker of lights to become noticeable (as it was on early 25Hz systems). The use of higher frequencies would cause increase in the operational losses due to eddy currents, hysteresis, skin effect, radiation etc. and reactive voltage drops.
In physically smaller power systems such as those on planes, ships, submarines and even railways, higher frequencies are used because they allow reduction in the power equipment size and weight - i.e. the optimisation is different.
50 Hz however, is not universal. Many countries use 60 Hz which is close to the same optimum as 50. 60 Hz users mainly are: almost all the Americas and some countries in Asia. Korea even uses both frequencies! 50 Hz prevails in Europe and ex-British colonies.
Although David F fails to answer your "why" question, he does provide accurate information as far as it goes. Mike 1942's is not really an "engineering" answer.Source(s): Lifetime in the power game
- monophotoLv 71 decade ago
System frequency is standardized for economic reasons - if the same frequency is used over a wide area, then it is possible to interconnect systems. That makes it possible to share reserve energy supplies across that area resulting in lower costs and improved reliability for everyone.
50Hz is NOT standard in all countries. 60Hz is the standard frequency throughout North and South America - with the single exception of the country of Argentina that uses 50Hz. Europe and Asia use 50Hz. Africa and the Middle Eastern countries are a mixture of 50Hz and 60Hz. Japan uses both frequencies - the northern half of the country is 60Hz, while the southern half is 50Hz. And within these generalizations there are also exceptions - Indonesia is a 50Hz country, but there is a large 60Hz system in Sumatra.
And there are a few isolated instances of other frequencies. Here in North America there are at least two small 40Hz systems, as well as a few 25Hz systems. In Europe, there is a smattering of 16 2/3 Hz (the rail system).
In the very early days of electrification, electrical loads were served by dedicated generation, so designers selected the frequency that they felt would result in the optimum design for loads and generation. Some of the early systems had frequencies as high as 135Hz. Eventually, as the desire for interconnection emerged, it became necessary to standardize on a single frequency. The choice between 50Hz and 60Hz ultimately came down to the kind of lighting that was in widespread use in the region being served. In Europe, the prevailing practice (driven mainly by Siemens) was to use an enclosed-arc form of lighting at 50Hz. In North America, the practice was to use an exposed arc form of lighting. Because the extinction time constant was shorter when the arc was exposed, there was a desire to supply those lights with a voltage that had a shorter period between zero crossings (to prevent 'flickering') - hence, the choice of 60Hz.
Systems of different frequencies can be interconnected, but this requires either complicated rotating machines or expensive power electronic devices. It's done (the 50Hz/60Hz interface in Japan is a great example), but in most places system planners choose to avoid that complication.
- Mike1942fLv 71 decade ago
The most direct answer to why is that British power companies adopted the 50 Hz frequency and the British Empire dominated the world at the time that power networks were being installed.
- David FLv 71 decade ago
It isn't. 60 Hz is standard in Canada and United States, and 400 Hz is standard in aircraft.