AC Power became popular because it can be transported over long distances without the voltage drops that occur in DC. Basically, voltage drops with distance through a conductor, so the high currents being delivered (to multiple distant power sinks) requires that the conductors have a very large cross section, which makes them very large, heavy, and expensive; i.e. impractical.

AC power can use transformers to step up the voltage, which reduces the current, which allows power distribution through much smaller conductors. At the ends of the distribution network, transformers are used to step down the voltage, which increases the current to the multiple power sinks it serves. There is even a miniature version of this in the local areas: I"m sure that you have seen these transformers on power poles.

As a side note: AC power transports much more effectively than DC, however AC power is a lot more deadly than DC.

The Gregg, DC is way more dangerous than AC. Example, USA electrocutes people using about 2Kv 60Hz AC. It takes several minutes, in some cases, to do the job. We, Australia, use 1.6KV DC to power our trains. No one has ever survived even accidentally touching the conductors. It blows you to bits! 60Vac gives you a tingle, 60Vdc will kill you. In fact, people using 12Vdc for prawning (shrimp) lights have been killed. DC is by far the most dangerous.

Last time I looked at the 16th edition (about 6 years ago), their safety philosophy was the other way around. From a safety perspective, 50V ac was equivalent to 120V dc (provided there was less than 10% ripple on top). It's the frequency of the ac which can cause fibrillation of the heart and kill you that way, rather than the heating effect of current. Go back to the old days, Edison said his dc was better than Westinghouse's ac because that was used to electrocute dogs.

Hi HUX, yes, it can be said that that DC is more dangerous than AC. I'm sure that many people that have never been 'STUCK' on the live wires will give you their varied opinions. I once grabbed the active in my left hand and the neutral in my right hand. 240Vac 50 HZ. I remember thinking that something wasn't right. Then realising what was happening. About 4 seconds later, the alligator clips that I grabbed, touched and tripped out the circuit breaker. It took about 9 months for the burn on my left index finger to grow out. Sure, my heart did try to beat at 50 HZ, being current flowing from one hand to the other, but at least it didn't try to just stop my heart. The fact that the current oscillates is what makes it safer. If you turn off a switch that is breaking a 240Vdc circuit, it must do it with speed and distance. I have witnessed first hand while doing an electrical trade the distance that a spark will jump and keep going with DC. AC, no continuous spark. The break in current flow due to frequency stops it. But DC, another matter. If the world were wired with DC power, it would be a different place. AC is better, Tesla was right.

Comparison between 50 and 60 Hz!

It is two different standards set by different groups of countries.

There could really not be any substantial advantages and disadvantages.

Unfortunately changing over to the other frequency would be costly.

Any application using an electric motor will have to change or adapted. (water pumps, air conditioning etc) Even garage door and security gates.

"60Hz is us, therefore it is good, right and beneficial.

50Hz is them, which means it is evil, wrong and detrimental."

Attributed to G.W. Bush

"Them" use several types of 50Hz. The Grid in the UK is not synchronised to The Grid in France, for example, though both operate at the same numinal 50Hz. Power is transferred between the two nations via an underground cable, and has to be converted to DC at the transmit end, and back to AC at the receive end.

John: 11, 35.

Oh, and "Them" use 220VAC, not like the 240VAC that "Us" use.

Some people even use 110-120VAC. How strange is that?

We harmonized to a nominal 230v ac. a while back...

It caused us a few minor problems with the slight reduction in voltage.

Del, the official change over or harmonised standard of 230 volts was a total bureaucratic load of nonsense...

In EU they have 220 volts in the UK is been 240 volts it would have cost a fortune in wasted power just in the transformers to make an actual change in voltage ....

So in Brussels wisdom the harmonised standard was changed to 230 volts with a tolerance which included 220 and 240 volts!!!

So no change except that it appears all nicely harmonised and a lot of EU Bureaucrats got paid for doing sod all!!!

Also, watch out, when buying electrical goods for the EU, in the UK the lifetime can be significantly less than in EU due to it being designed for a lower voltage working!!!

Good stuff this EU ain't it?

So in Brussels wisdom the harmonised standard was changed to 230 volts with a tolerance which included 220 and 240 volts!!!

WRONG ! After the change from 110 to 220V in EU (yes they DID the step !) they saw that the network still would not be sufficient over the coming years. So they GRADUALLY are raising the voltage over several years. The final voltage will be 240V. By that time, the same copper lines will transport about 10% more energy. In the beginning you saw electrical stuff made and marked for 220V, now manufacturers make their stuff for 230V, and in a few years you'll see it will be 240V.

Since when did the EU run a 110 volt system?

I know the long time aim is to use the same voltage but in the meantime its a total fudge, by increasing the tolerance of the voltage no action has been needed.

The final harmonised voltage is to be 230 volts from what I remember, I stand to be corrected on that though.

Blimey Guys... will someone just stick their meter across mains and get back!?

I did actually notice a reduction from 240 -230 but I am frightened to admit it now else I may get labelled a heretic..

I vaguely recall phoning the local powerstation at Broxbourne at the time!

I'm going to hide under the stairs now!

I am sorry Electroman .... By saying 110V I actually meaned 127V (220/sqr3) But because at the outlet wasn't measured much more than 110, people commonly talked about 110 Volts.

And by saying "EU", I actually meant : "the countries on the european continent".

I am not sure about the date of the change over from "110" to 220V. But is was during the fifties. They did it piece by piece (block by block), because the only thing they did, was exchange the Neutre with a Phase. I clearly remember that every family got a free transformer and a few 220V lightbulbs.

The change from 110 to 220 was necessary for two things.

First of all, they could push 1.73 times more power through the existing cables.

Second : New power stations that produced 380 Volts for the industry, could also provide 220 Volts (1 Phase + Neutre)

The "sliding up" issue was told me when I was working in the Nuclear Power Plant in Antwerp. I guess those people who produce electricity knew what they were talking about, no? *S*

What has been said or written in Brussels was probably just an easy was to explain the "fluctuation" between 220 and 240, what actually only seems to go UP.

Note : Not only the 220 goes up little by little, but also the good old 380V climbs little by little to 410V.

Hi 44m (catchy name huh?) I didn't know about the 127 volt change in the 50s, and if you have your information from good sources that's fine by me....

I'm only remembering what was said in the trade press a while ago, so it may well have changed now.

Its difficult enough to keep up with the latest changes in regulations for the electronics side of things let alone the electrical supply side....

Oh well, just as long as the supply doesn't change from 240 to 0 volts!!

John.

"60Hz is us, therefore it is good, right and beneficial.
50Hz is them, which means it is evil, wrong and detrimental."
Attributed to G.W. Bush

yeah JRaef ... maybe a good reason for you and GWB to start another war ...

Maybe I'm way off here...but I don't think the the difference between 60 and 50hz is enough to make much difference to most electrical devices.

A 50hz transformer is fine on 60hz and vice versa...dunno about motors. But I wouldn't be too worried about trying a smallish motor (say 1hp).

You can't swap between 400hz and 50...because it's a big difference.

I'm braced for incomming flak here!

depend on what you use it for.

film projection have to be synchronize with 18 vews second or 24 view or 28 view/second, and many authers applications

Most newer test equipment accepts 47 to 420 hertz input power. Before DC motors became popular 50 to 60 hertz was a problem. Voice recording/playback equipment had to be modified. Older microwave ovens taken from the US to Europe would over cook the meals because the timer and turn table would run slower that intended. As for the 400Hz applications, during the early years(vacuum tube technology) of aviation, 400Hz used smaller components. A power supply transformer for a 400Hz application was half the size and weight of a transformer used in a 60Hz application. Modern avionics has pretty much become a DC input application. Due to the amount/age of ground support equipment, swapping over to a 50/60Hz system will not happen anytime soon in aviation.

Electric motors, transformers in fact any equipment with an iron core will, on 60hz, have 5/6 th of the core CSA [refer to the induction formula]. Consequently much smaller overall and thus less expensive than the comparable 50 hz equipment. Thus, 60 hz designed equipment when run on 50hz will have a lower reactance, run hotter & in the case of rotating machines, run slower [5/6th of the 60hz speed].

50 hz equipment run on 60hz will behave in the opposite fashion to that described above.

Greg Lynch

country like USA And Jappon prefer 60hz they said it cost less for a motor with this and, the countries in europpe like France and auther think it more safe to use a 50hz.

In thier obstination they were looking to be deffrente one to the auther

you have to know that all technology around that two systems have a lot of diffrences ex: for tv signal in europpe, and most auther contries like Brazill you have system with 50hz they call it Palm or secam and then for US and Jappon you have NTSC signal some magnétoscopes from France can read all those but it cost a lot. you can have transformers in Europpe to convert 60hz to 50 hz. it doesn't matter for light, bulb

Walter F.

Transformers can not actually convert 60 HZ to 50 HZ. Transformers convert voltage from one to the other, such as 240 VAC to 120 VAC. Frequency conversion must be done by first converting the AC to DC then converting back to AC using the oscilator frequency of choice. Much more complicated than a transformer. Another way to do it is to use a motor connected to a generator. We used a 60 HZ motor connected to a generator and adjusted the rotation of the generator to 50 HZ in order to check out equipment we were sending to a 50 HZ market. This was necessary primarily because of the large load that we were placing on the power source.

Most offen They use 220 volt for 50hz and 110 volt for the 60hz. by using a transformer for voltage you'll still have a diffrent: more or less rotation for all AC motor and some machine have a compensator swiching betwen 60hz or 50 hertz. Contries use one or other to allow preference for electronic and electric appliance in their economic area.

Could be a slight problem for electric alarm clocks (clock radios).

greg you have the best answer to the 50/60 hertz question. the first ac water powered generators were 25 cycle, I believe because of shaft bearings many old appliances were marked 25-60 cycles. possibly one reason for 50 hertz was because of the metric system one hertz =20 milliseconds also early light rail ran on dc, but the motors would also run on the 25 hertz which could be transformed. perry

The definition of the "Hertz" unit is "cycles per second". Therefore one Hertz equals one cycle per second. Your figure of 20 ms is the amount of time required for one cycle at a frequency of 50 Hertz. I'm sure you know that, but I found your statement confusing.

I've found this whole thread interesting to read, but so far no one has really answered the whole question, especially the second part, which asked for a comparison of the two systems, in terms of their relative advantages and disadvantages.

One advantage of 60 Hz is that, much below this frequency, the human eye can detect the flicker of electric lights. Having never been to Europe, I don't know if this effect is offset by doubling the voltage as they do. I believe that if America were electrifying today, it would choose a higher working voltage, as Europe did, to reduce current.

Hmm... When we were designing Pachisuro (slot) machines for the Japanese market, they were running on 50Hz. There were a lot of design changes made to convert from 60Hz used in the States. Functionally, there was no inherent advantage either way, but you have to design for your target market.

This has been discussed at least once, also this year on CR4, so why not search thru the archives and read those before starting it all over again?

Read also:

Frequency Problem <http://globalspec.ip09.com/rd/9z1zq2qt0g20m52u2j7lb19as5edj9qfpv225mhn6g0> (Electrical Engineering)

Hi, guys you just think over Hysteresis and Eddy current loss, this is a function of frequency. higher frequency means higher loss.

check and explore!!

1. There are some more Frequencies used certain Countries eg 45Hz
2. 400Hz used by Aviation internationally.
The reason is the weight of Power-Units of avianoic-equipment.

Note: This alone reason saves a lot of Copper & Core-material of Wound Components like transformers, motors etc. But it is impossible for a community or country to go to the other sysem. It involves un-immaginanable financial involvement & years of ..

I remember when due to Hydro-electric developements in my country a few towns using DC supply were converted to AC in almost 5/6 years only due to ceiling-fans & a few Saw-Machines in Wood cutting small setups. It was 1950s.


3. At higher frequency the lighting-flicker effect is lower than the lower freqs.
4. Decision to adopt 50, 60 or else & voltage for Electrical-Power was decided by each county's Technocrats at that time and what-ever was decided cannot be reverted to the other just by discussions but a lot of financial effect is involved which over-do any advantage [if any].
All the systems adopted have pros & cons.

5. Frequency also have major impact on Video [Films etc etc] as the number of frames/sec are different and for the same reason TV's standards.

238 volts in Harlow this afternoon!

WOW exciting eh?

You'll make a great meteorologist Del. What's the low for tonight?

The original nominal voltage in the UK was originally to be 250/440v and after nationalisation, the national standard was confirmed at 240/415v.

European harmonisation is basically about everybody trying to agree the same thing without upsetting any body.

Most of the European countries had a 220v so the UK was the odd one out, rather than upset us they settled on in splitting the difference at 230v and the UK changed its voltage tolerance from 6% either way to 6% below and 10% above. This was a godsend to many electricity companies who in some cases needed major expenditure to correct supplies which were 6% below 240v, but now became OK at 6% below 230v. Many of our many HV transformers have tapping settings to adjust outputs and this can accommodate any out of tolerance voltages. Only the very small local distribution transformers tend to have no tapping adjustment.

The frequency is more critical it is determined by the number of poles on generators at power stations and the speed of the machines. The standard 50Hz in the UK requires a constant shaft speed of 3000rpm to maintain this frequency. Any change in frequency is very hazardous, it affects all rotating machines from the analogue clocks right up to crane drive speed, and frequency dependent equipment. Most important of all - change in frequency can lead to resonance conditions in both installations and supply systems.

One of the most important pieces of protection of generators and the grid is frequency relays which cause disconnection if it changes 0.5Hz either way.

We can never change our frequency without changing our power station and grid system protection. In technical terms the difference between 50Hz and 60Hz is so slight ther is no great benefit benefit or disadvantage between the two, but you do wonder how the US came up with such an odd number in the first place.

I would agree with most of that Guest, except for one point.

I believe that the small local distribution transformers do indeed have tap chages on them...

These are usually mounted at the top of the pole and are essential for long runs in the countryside where the voltage drop of the wire needs the taps to be altered to compensate. i.e. 10 mile wire run with a 10% drop needs the transformer to be set to 10% higher output. Essential in the farming community.

John.

AC voltages are easily converted up or down with transformers. However frequencies are much harder to convert. U.S. armed forces members and their families stationed in Europe know these facts well. They buy small step down transformers that convert Euro 220V down the the 120V that their American toasters need. That old vinyl record player they brought along is a different story: it will run slow. The reason is that is has an induction motor that was designed to be synchronous at 60 Hz, it's now synchronised at 50 Hz and that is indeed 5/6 the speed needed for the records to sound OK.

World wide, everybody started out generating DC power, but the need to convert the voltage up for transport and back down for the consumer was a challenge. Motor-generators could do it but switching to AC power and using transformers was far less costly. Most countries started at 25 Hz but found efficiency increases as the frequency goes up. European countries followed metric traditions (base ten) and went with 50 Hz. The U.S., with no common measurements except for time keeping, went with time. (60 seconds to the minute, 60 revolutions to the second.)

Technically speaking, the iron core of a transformer, or an induction motor delivers a fixed amount of energy every time the magnetic field in it reverses. Sort of like scooping cups of water out of a bucket: the more cups per minute, the more water moved. Because of this the core of a motor or transformer transferring equal power can be 5/6 smaller when running at 60Hz vs. 50Hz. This is the reason 400Hz was adopted for aircraft since electrical devices could be made much lighter.

That's also why the power transformer in an old TV weighed 10 pounds but the power transformer in a PC power supply weighs 4 ounces. Both transfer 300 watts, the difference is that the PC transformer is operating at 25KHz instead of 50 or 60 Hz.

Nice post Zamaron (and Jraef)!

Thanks Zamaron, it's about time someone made sense.

Funny how the OPs question was only about Hz, yet so many people went off on the voltage tangent!

Focus, people. Focus.

In all seriousness though, this is a moot point, it's like arguing about whether the sun will come up from the left or the right. The only thing that matters is your point of view.

Frequency is what it is wherever you are. There is no real "advantage" over one or the other. There is no place left on this planet that does not have some sort of power available now already, so to debate this is meaningless because the only purpose in debating it would be if you were needing to "choose" one or the other for a new grid system. Here in North America, it would be completely asinine to choose to develop a 50Hz grid; it would be incompatible with everything around me. If I were in England or India, the same would hold true for trying to develop a 60Hz grid.

If anyone must know the HISTORY behind it all, the real answer for 50Hz is indeed the 20ms issue with regards to 50Hz being chosen in Europe, because 20ms x 50Hz = 1000ms; neat and clean... if your world makes sense when divided up into neat chunks divisible by 10's and 100's and 1000's etc. In the US, Tesla and Westinghouse chose 60Hz because it was evenly divisible by the number of seconds in a minute, as in motor speeds being measured in "Rounds-Per-Minute"; 60Hz = 60 cycles = 1 Cycle per second; neat and clean... if a 60 second clock is the basis of your thinking. Is either one right or wrong? No, just different points of view.

Interestingly enough though, someone brought up Japan earlier. That is a prime example of the stupidity of "choosing" in mid stream. Most of Japan was 50Hz up until WWII, but after the long US occupation, large parts converted to 60Hz. Now they are stuck with both! It's a mess, although they have adapted to it well I must say.

Good post..

(It comes up on the Left..)

Nice article, Mr. Raeff, only one remark : What has 60 rounds per MINUTE to do with 60 cycles per SECOND ? It makes an even more odd number : 60 times 60 is 3600 !?

Anyhow ... With the newest frequency inverters, all our 60/50 or 50/60 progs are solved ...

What can I say? It was late at night when I posted that!

The 60 was chosen based on a clock cycle however, of that I am sure (at least, from reading in a textbook years ago, for whatever that's worth).

Here´s how a thorny businness and diplomatic issue between two countries involving billions of dollars was solved by the use of the two standards. The huge hydroelectric dam Itaipu is a 50/50 joint venture between Paraguay and Brazil. 50/50 means that the power output is divided equally since the Itaipu river belongs to the two countries. Paraguay is a mostly an agribusiness country, a midget compared with giant power-hungry Brazil. So Paraguay takes a little power for the country needs and sells the rest to Brazil, which seems never to have enough. Now here´s the catch. How is small Paraguay to protect herself from being ripped off? Answer: One half of the the 10 turbines belong to Brazil and one half to Paraguay. Brazil turbines are set for 60Hz and feed right in to Brazil´s power grid. On the other hand Paraguay turbines are set for 50 Hz feeding electrical substations on Paraguay´s side of the border. Here power transformers convert to 60 Hz for selling to Brazil and Paraguay´s own use.

Really? A "power transformer" that converts 50Hz to 60Hz? Pray, tell us how that is accomplished?

I'm just teasing you though. Your story is correct, it's just that they are "converters" not transformers. Probably just a translation glitch. And actually there are 18 generators, 9 are 50Hz and 9 are 60Hz.

And this brings us to the only advantage of one system over the other. At 1800 RPM for a 4 pole machine or 3600 RPM for a 2 pole machine it is possible to extract more power from the prime mover in smaller sizes that were around historically. The 60hz is kind of a hot rod system. In larger systems this advantage seems to have largely disappeared. I looked the Warszilla site the other day and the power ratings for each frequency were the same in the multi megawatt sets.

Transportable sets are still often rated higher for 60hz than 50hz. The gain in specific power is likely offset by increased maintenance costs per operating hour, but relatively constant per kilowatt hour.