Why do we have different frequencies and supply voltages in different parts of the world?what are the advantages and disadvantages of using higher frequencies and lower frequencies for supply voltage?How do we choose the moderate frequency range ?
In some countries we have 50hz and in some countries 60hz..and supply voltages also differ..
for example in united states,they use 120volt,,60hz..if we use this voltage the current through transmission lines would be very high..so..there will be great power loss..even then they use like that ..why do they do so?
where as in india ,we use 230 volt,50hz to reduce loses..which one is better and why?

 

in the US, houses use 120 V. The power comes from distribution lines that carry 3 ph 14,400 volts. the higher voltage lets high power be distributed with smaller current losses and lets the system use smaller wire. the power leaves generating stations at up to 1 million volts.
120 exists only in plug outlets and light sockets. overhead wires carry 14.4 kv minimum, and often much higher voltage.

 

the frequency was decided on many years ago. 60 hz means power transformers use lkess iron in their cores, 50 hz transformers and motors are heavier. europ uses 50 hz because they do. the usa uses 60 for much the same reason. the best part is the standardization of frequencies, so the grid can be mationwide, and clocks keep porper time. there are a few parts of the usa that use lower frequencies, and some inductries also have their own lower fredquencies for their own reasons. 25 hz is sometimes used in industry and transportation.

 

in the US, houses use 120 V. The power comes from distribution lines that carry 3 ph 14,400 volts. the higher voltage lets high power be distributed with smaller current losses and lets the system use smaller wire. the power leaves generating stations at up to 1 million volts.
120 exists only in plug outlets and light sockets. overhead wires carry 14.4 kv minimum, and often much higher voltage.

do you mean to say that people in US use all of their loads which would be fit for 120V?(i mean all the loads such as grinders,motors,etc...)

 

no, 120 volts is not the only voltage used, normal voltage to houses is 240 split phase, 2 120 volt phases with common ground. industrial uses 480 three phase and there is even some 208 volt three phase used too. where I work, most small stuff is 120 volt, lighting is 208, and motors are mostly 480. some compressors and large pumps use 4160 volts, and there are a few plating rectifiers using 12700 volts.

 

do you mean to say that people in US use all of their loads which would be fit for 120V?(i mean all the loads such as grinders,motors,etc...)

Most household items are 120V. Lights, handheld electronics, TVs, audio equipment, and so on. Large (>15A, 1500W or so) loads such as electric stoves, air conditioners and such will usually be 240V.

 

Why do we have different frequencies and supply voltages in different parts of the world?what are the advantages and disadvantages of using higher frequencies and lower frequencies for supply voltage?How do we choose the moderate frequency range ?
In some countries we have 50hz and in some countries 60hz..and supply voltages also differ..
for example in united states,they use 120volt,,60hz..if we use this voltage the current through transmission lines would be very high..so..there will be great power loss..even then they use like that ..why do they do so?
where as in india ,we use 230 volt,50hz to reduce loses..which one is better and why?

In the UK, some supplies were as low as 25Hz. there were at one point quite a few DC power stations.

There were pretty much only half-assed attempts at standardisation prior to WW2.

 

The advantage to 240v U.K. etc for general appliance etc over the 120v in N.A. is a smaller conductor is required for a particular load on 240v.
There is a difference in N.A. for 3 phase power, in US it is mainly 208-220-480, in Canada 208-220-575/600.
Max.

 

Thank you very much for your replies to each and every one...but most of you gave me the answers as why use 120v in US..my question is -why do we use such different voltages and frequencies in different countries ? please explain me about this point...

 

power generation and distribution started at the same time in places all over the world. Each one served only their local area. All of them began as a business. A national/global "grid" is a very recent thing.
each and every one did it the best way. According to them. Market forces decided who was best and those enterprises grew quickly. Then the AC DC battles began.
why am i repeating all this. go to wiki and read all about it

 

It is not about the physics of electricity so it must be about who was in charge when the standards were decided.

 

I think that there would be some reason behind it...its neither about the in charge at that moment nor about serving the local area...please give me a good explanation..i am eagerly waiting for your replies...thank you

 

Hello,

You might want to read this wiki page:
http://en.wikipedia.org/wiki/Mains_voltage

Bertus

 

the laws of physics and mechanics do have something to do with the choice of frequency, one of the first uses of electric power was clocks, and synchronous motors rpm is set by the number of poles and the line frequency. so 60 hz made for standard gear ratios, just like 50 hz did also. but 60 hz had less flicker in lights than 50.

 

Freq. was often set merely by the number of poles on the generator snd how fast or slow you could get the steam engine running.
16.3333 Hz, 25 Hz, and 40 Hz were common where electric traction motors were run. The lower freq. was better on those. higher freq generators also were used. 100 Hz and up were common on lighting systems, and 1000-4000 Hz systems could be found on many. arc lamps gave good service at high freq. Go read some history. I don't think anyone here is going to go to trouble of writting out a multipage essay on this for you to copy down and turn in as your own.

 

simplification of generstion and distribution and to get more paying customers so scale could be reduced to increase ability to compete with rivals. when large city wide systems got up and running, people naturally wanted more access in more areas. Operators discussed mergers and that meant more standardization was needed to grow systems together and make larger utility companies. Business needs drove the consolidation of small compsnies into big ones and that drove stsndards to evolve into a single specificstions for nations and the next step to come in the future will be a global one.

 

the laws of physics and mechanics do have something to do with the choice of frequency, one of the first uses of electric power was clocks, and synchronous motors rpm is set by the number of poles and the line frequency. so 60 hz made for standard gear ratios, just like 50 hz did also. but 60 hz had less flicker in lights than 50.

Synchronous clocks were a fairly late development in the UK, power stations were popping up like mushrooms with anything from 25 - 100Hz.

Not sure - but there may have been a few DC power stations right up to WW2.

AFAIK; the national grid was being implemented before WW2 - the idea was, if a power station feeding a vital installation got bombed, it could still be supplied by overhead cables from power stations in the surrounding area.

The 400kV pylons didn't go up in my town until the 70s - they built a whole new motorway and sited the pylons alongside it.

 

I seem to have been corrected. The chosen frequencies were related to some laws of physics, but more on what kind of generator was available instead of how the frequency acted when connected to a distribution grid consisting of miles of wiring.

I have seen a 5 HP 400 Hz motor that you can hold in one hand. That made me wonder why anybody would choose 50 Hz or 60 Hz. I see there are a lot of reasons.

 

It is often the case that those that come later benefit from the learning mistakes of the original implementer's of a system, for example the BBC (UK) were the first to broadcast a public TV system based on a low line standard of 405 lines, In N.A. the improved scan rate of 525 lines was implemented, the converse was when N.A. was first in the colour tv field with NTSC (often called Not the Same Colour Twice) , and later the UK used the supposed superior PAL colour system, and 625 lines.
I also think it rare for anywhere but N.A. to use a dual voltage residential power system?
Max.

 

I also think it rare for anywhere but N.A. to use a dual voltage residential power system?

Yebbut...we get less dead noobies learning about house wiring.