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# Why we use 50Hz, 60Hz or 400Hz frequency?

Why the frequency of power supplies in European and Asian countries is 50Hz, while American countries use 60Hz power supplies? What is the basic of the standard? What are the advantages and disadvantages of 50Hz and 60Hz power supply? In addition, why the airport and aircraft use 400Hz frequency?

In fact, there is no big difference between 50Hz and 60Hz, only the generator speed has slightly difference. Choose 50Hz or 60Hz, it's almost always the same in a country except Japan (Japan has both 50Hz and 60Hz power supplies).

We should be aware that why use 50Hz or 60Hz, rather than lower or higher frequency.
In electrical system, frequency is a very important basic element, not arbitrarily determined. It looks like simple, but in fact, it is a much complex issue, involve with many aspects. From the principle, we should mention the classical electromagnetic theory found by Maxwell, Hertz added a critical point for Maxwell's theory, Faraday's law of electromagnetic induction and the world's first electromagnetic induction generator, the British engineer Ward King made the electromotor first, the French Pixie made generator, Siemens found the generator principle, the invent the power generation machine, which is the first case in practical application.

Since then, it was found and summed up the theorem that the cyclical changes in the direction of the current is called alternating current, the time of the current in one cyclical change called the cycle, the cycle times of the current changes in one second called frequency, the unit is Hertz (in order to commemorate the contribution of German physicist Heinrich Rudolf Hertz). The frequency of alternating current is 50(60) Hz, the current direction changes 50(60) cycles, 100(120) times per second.

The electric motor is made according to the basic principle of the rotating coil in the magnetic field. If connect two copper slip rings respectively to the ends of the motor coil and two brushes connect with the slip rings, it becomes an alternator (principle). Generator is a device to achieve the conversion from mechanical energy to electrical energy.

Frequency value is related to the structures and materials of generator, motor and transformer.
50Hz generator synchronous speed is 3000rpm, if the frequency is 100Hz, then the synchronous speed will be 6000rpm. Such a high speed will bring a lot of troubles to manufacture the generators, especially the rotor surface speed is too fast which will limit the generator capacity greatly. In actual applications, the high frequency will make the reactance increase, electromagnetic loss, and increase the reactive power. Motor, for example, the current will decrease greatly, the output power and torque will decrease evidently, which does not has any benefit. In addition, if use a lower frequency such as 30Hz, transformer efficiency is too low, not benefit for AC power transformation and transmission.

The frequency in modern power system is the frequency of the sinusoidal fundamental voltage generated by the synchronous generator. Frequency is the unified operating parameter in the whole power system. A power system has one frequency only. Most Asian and European countries use 50Hz frequency. American countries use 60Hz. Most countries regulate the frequency deviation between ±0.1~0.3 Hz. In China, the frequency deviation of 3 million kW and higher power systems shall not exceed ±0.2Hz; lower than 3 million kW power systems shall not exceed ±0.5Hz.

The difference in grid frequency depends on different calculation habits.
The large-scale power generations in America are earlier than other continents. At that time, the calculation tool was British (duodecimal number system) slide rule. For easy calculation, they used 60Hz. And then later, the power grids use decimal calculation, 50Hz is more convenient.

List of worldwide mains frequencies:

 Country Hz Country Hz Country Hz Country Hz Country Hz Country Hz Afghanistan 50Hz China 50Hz Greece 50Hz Kuwait 50Hz Norway 50Hz Sudan 50Hz Algeria 50Hz Colombia 60Hz Guam 60Hz Lebanon 50Hz Oman 50Hz Surinam 60Hz Angola 50Hz Congo 50Hz Guiana 50Hz Libya 50Hz Pakistan 50Hz Sweden 50Hz Antiqua 50Hz Costa Rica 60Hz Guinea 50Hz Luxembourg 50Hz Panama 60Hz Switzer land 50Hz Argentina 50Hz Cuba 60Hz Haiti 60Hz Macao 50Hz Paraguay 50Hz Syria 60Hz Australia 50Hz Cyprus 50Hz Hawaii 60Hz Majorca Island 50Hz Peru 60Hz Taiwan 60Hz Austria 50Hz Czech 50Hz Honduras 60Hz Malagasy Rep. 50Hz Philippines 60Hz Tanzania 50Hz Bahamas 60Hz Danmark 50Hz Hong Kong 50Hz Malaysia 50Hz Poland 50Hz Thailand 50Hz Bahrain 50Hz Dominican 60Hz Hungary 50Hz Mali 50Hz Portugal 50Hz Tobago 60Hz Bangladesh 50Hz Ecuador 60Hz Ice Land 50Hz Malta 50Hz Puerto Rico 60Hz Tonga 50Hz Barbados 50Hz Egypt 50Hz India 50Hz Mauritania 50Hz Romania 60Hz Tunisia 50Hz Belgium 50Hz EI Salvador 60Hz Indonesia 50Hz Mauritius 50Hz Russia 50Hz Turkey 50Hz Bermuda 60Hz Equatorial Guinea 50Hz Iran 50Hz Mexico 50/60Hz Rwanda 60Hz Uganda 50Hz Bolivia 50Hz Faeroe Islands 50Hz Iraq 50Hz Mexico 50/60Hz Saudi Arabia 50/60Hz United Kingdom 50Hz Brazil 50/60Hz Fiji 50Hz Ireland 50Hz Monaco 50Hz Saudi Arabia 50/60Hz Uruguay 50Hz Brazil 50/60Hz Finland 50Hz Israel 50Hz Morocco 50Hz Scotland 50Hz USA. 60Hz Bulgaria 50Hz France 50Hz Italy 50Hz Mozambique 50Hz Senegal 50Hz Venezuela 60Hz Burma 50Hz Gabon 50Hz Jamaica 50Hz Nepal 50Hz Singapore 50Hz Viet-Nam 50Hz Cameroon 50Hz Gambia 50Hz Japan 50/60Hz Netherlands 50Hz Somalia 50Hz Virgin Island 60Hz Canada 60Hz Germany 50Hz Japan 50/60Hz New Zealand 50Hz South Africa 50Hz Western Samoa 50Hz Central Africa Rep. 60Hz Ghana 50Hz Jordan 50Hz Nicaragua 60Hz Spain 50Hz Yugoslavia 50Hz Chile 60Hz Gibraltar 50Hz Korea 60Hz Nigeria 60Hz Sri Lanka 50Hz Zambia 50Hz

The special circumstances in airport: aircraft generators require small size, light weight, the only way to meet the power requirements is to increase the frequency, so the corresponding electrical equipment on airplanes should be 400 Hz, and aircraft-related power supplies is 400 Hz, military uses even higher frequency.

Aircraft power supply uses 400Hz is in order to reduce the size and weight, it is a complex system. 400Hz being used on military and avionics is mainly depending on the following: 1, High frequency generator or electro motor has small size and light weight due to the high rotating speed and low torque; 2, The aircraft generator is driven by the aero engine, it has high speed; 3, Aircrafts have lots of DC machines, high frequency is benefited for reducing the rectification ripple.

In case of same voltage, what are the differences of 50Hz, 60Hz and 400Hz power supplies in transmission and efficiency?
The reason of not using 100Hz or 120Hz is due to the high frequency, on the one hand, the transmission will be difficult; on the other hand, it's inadvisable to increase the speed or poles of the generator and electro motor. 400Hz power cannot be transmitted for long-distance, the user needs to regulate the transmission distance and method before ordering a 400Hz generator, and the rectifier efficiency will be poor, but the rectifier ripple is smaller, the ripple frequency is higher and good for handling.

#### Leave your comment (Registered user only)

12/8/2020 7:11 PM
So if you look at some train operations, they use a 25Hz frequency; presumably to provide greater transmission efficiency.
4/25/2020 10:24 AM
I don’t want to sound mean but this article was very difficult to read and there are many grammatical and spelling errors throughout. Perhaps you should consider proofing the documents in a word processor first such as Microsoft Word before publishing to make sure that doesn’t happen.
10/6/2019 5:58 PM
Very useful information. Well done.
7/24/2019 10:54 AM
nigeria uses 50hz and not 60hz as seen on your chart.
5/7/2019 12:51 AM
50 hz is economical . This hz we get at 1500 rpm and 4 pole generator.
10/11/2018 4:32 AM
can i coonect 50/60 Hz motor to aircraft power supply with high 400 Hz with same voltage output .
3/18/2018 5:27 AM
What is the benefits if we use 100HZ motors?
2/28/2018 7:01 AM
what is your source? plz mention it
12/19/2017 3:06 AM
Frequency, a wave that cuts one second into a regulated space and then attends to count the highs and lows within a frequency.
I can image this occurring, and thus I grow!
Thanks!
10/28/2017 6:07 PM
FYI: Hawaii is not a country.
4/6/2017 6:57 AM
I've always wondered what 100V~ 400Hz means on my C.P.AP. machines power block. Thank you!
3/10/2017 8:07 PM
In tanzania we use 50hz or 60hz?
2/1/2017 9:00 PM
Norway uses 50hz 240V IT / tt. but 50hz 400 volt tn is getting the new standard, which is gradually Introduced, with Expansions and new construction.

So pleace correct list Norway 50hz