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# Why frequency of power line is 50-60 hz?

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#### saman1980

##### Newbie level 4
Why 50 hz?

Does anyone know why frequency of power line is 50-60 hz?
We accept that as basic rule.

Why 50 hz?

because if it were below 50Hz, we would see an annoying flicker in bulbs. and it gets expensive to generate and transmit above 60Hz.

Re: Why 50 hz?

techie said:
and it gets expensive to generate and transmit above 60Hz.

Cud u plz explain this statement? To increase the freq. why can't we just increase the rotation speed of the generator or the number of poles.

Why 50 hz?

increasing poles means more cost, icreasing speed means more losses and more wear-n-tear. Also higher the freq, higher the line-loss (higher impedance,more skin effect, more corona losses etc etc)

Re: Why 50 hz?

i don't think we would choose the same frequency again if we could choose it. But nowadays all devices work on this frequency so we're stuck with it.

Re: Why 50 hz?

I think, it's a mechanical problem, cause turbines in power engines, can not rotate too high. speed So people decide some time ago (I think more than 100 years ago) to use 60Hz in some countries, and 50hz in other countries. Nowadays, it's become an universal frequency in all power lines.

Why 50 hz?

Its always a tradeoff between a few parameters. One problem rises with frequency, the other decreases. You have to select a tradeoff point. The fact that people in different locations chose close freqs of 50 and 60 hz proove that this is the right frequency range. if we were to choose it again, we would still choose the same range

Why 50 hz?

I don't think any explanation has ever been given about the choice of 50Hz as power tx freq. The above discussions above have been mere speculations only.
The choice of freq seems merely historical.

Re: Why 50 hz?

magnetra wrote: The above discussions above have been mere speculations only.
The choice of freq seems merely historical.

magnetra Certainly it will not be historical......

high frequency means skin effect....and may be cost more for this..
less frequency means will get blinking effect on our light bulbs......
mquestion is why not 55Hz why not 53Hz why always to either 50Hz or 60 Hz?

Re: Why 50 hz?

Hello people,
I don't believe 100Hz suffers from skin effect neither 200Hz.
The problem is that, a diesel engine driving a generator at 1500rpm produces 50Hz, so for 100Hz 3000rpm are needed and for 200Hz, 6000rpm.
That means, lower efficiency of engine and more wear of all parts. So at the time a decision was to be taken, the 50Hz was a good compromise.

Why 50 hz?

Ok the skin effect is not that large. But higher frequency means higer inductive and capacitive impedance causing larger voltage drops and thus needing more expensive transmission hardware.

Re: Why 50 hz?

Somebody here told that why cant 53 or 55 Hz..Bcoz..
1.we always try to design the generator for even no of poles ..
2. Turbines cant rotate at high speed due to centrifugal action..
3. Skin effect dominates at hig frquencies..
4. Lumped analysis cant be done at hifh frequencies..
5. Bulbs flickering would b high at low freq.s
All these constraints can be satisfied only for 50-60Hz freq. rannge....
But the adv of using high freq. are device size reduces..

Re: Why 50 hz?

hi!

Why 50 hz?

For light, the human eye is able to see a picture with a frequency of 60Hz. That´s the strobo or strobe (not sure) effect. Some times you can see a moving well as it was stoped, that´s a consequence of this effect. Because of this, when you have a 50-60 Hz oscilattion on the light source (actually 100-120 Hz + and - cycle), you don´t notice this.

Re: Why 50 hz?

@ penrico, @ maharshi_qis: Your explanaitions is noncense. Why?. Did you ever hear about machine transmitters ?. No ?. Start reading it and you will never tell this story again.
The real reason ?. 50 Hz ?. Transformers are acceptable small, since a lower frequency will increase the core size. The higher is difficult if you power lines are long I mean 100Km etc... your losses will go up very quickly. That is why they sometimes use DC instead of AC for very very long powerlines in Europe and Russia, do not know about USA though.

For all those here who believe the generator can't make higher frequencies than 50Hz should read this: https://en.wikipedia.org/wiki/Alexanderson_alternator

Why 50 hz?

I seem to recall that Tesla's laboratory used 166.6Hz until he came up with a motor that needed a lower frequency to run correctly. I should look into this.

Why 50 hz?

high frequency means skin effect....and may be cost more for this..
less frequency means will get blinking effect on our light bulbs......

For all those here who believe the generator can't make higher frequencies than 50Hz should read this: h**p://en.wikipedia.org/wiki/Alexanderson_alternator

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