A man is walking down the street and clapping his hands loudly.
He is asked:
"Why are you clapping your hands?"
"I'm killing crocodiles!"
"There are not any crocodiles!"
"That's because I broke them up!"
Old anecdote
The anecdote given in the epigraph very well reflects the situation with the constant in the network. All with it successfully struggle. Internet forums are full of stories about how the equipment sounded better after installing a filter that eliminates the constant voltage in the network. Only here the idyll spoil three tiny moments:
The danger of constant in the network for transformers is declared speculatively. How much this all worsens the work in reality - I have never met such research.
Half of the schemes proposed to eliminate the DC voltage from the network, in fact, do not, and some of the most unfortunate schemes also add interference.
None of those who removed the constant voltage in the network and immediately so well heard the improvement of sound, this is the most constant voltage in the network did not measure at all! And absolutely not in the know - it was there, or it was not at all! Nevertheless, the constant of type successfully deleted and the sound improved.
In general, the dispersal of crocodiles is very successful.
There are many people convinced that the devices included in the network need to be protected from constant voltage. And from a number of other things present in it besides the voltage of 220 volts 50 hertz. They are supported by sellers of expensive (at least $ 1000) devices, called air conditioners.
There are also a lot of people who think that all this is garbage - all the devices included in the network, perfectly work and without network air conditioners. Even high-voltage interference is not very terrible - in the extreme case, the varistor has been installed, and all the cases. Moreover, there are certain GOSTs and norms for the quality of electricity, and in all our contracts with its suppliers, the compliance of energy quality with the standard is guaranteed.
Both these groups argue on Internet forums right up to swearing. Who is right?
On the one hand, the network is a very stable thing. On the way from the power station to the consumer, the current passes through a series of powerful transformers that cut off both direct current and anything that is very different from the frequency of 50 Hz. On the other hand, the transformers are not ideal (and transient processes in transformers are generally something!), And even from the transformer to the end consumer's apartment, a long wire with both resistance and inductance (and catching RF interference at the same time). And quite near, at neighbors behind a wall, any "evil" device can work. Unbalanced for both half-periods of the network, the load gives a constant component, and the transformer that can suppress it is too far away. Fantastic? And you look at the real network. Its peak factor, measured by me in several areas of my city, is somewhere around 1.35 instead of 1.41. This is because of the "cutoff" of the tops of the sinusoid by numerous power supplies. Those. the sine wave in the network looks "more flattened" than it should be. And where is the correspondence to GOSTs? By the way, transients during switching of a powerful load can be very unpleasant. In theory, the devices included in the network should not interfere with the network ... Do you believe in the idea?
But the most important thing is that all statements of both supporters and opponents are permanent in the network - they are speculative! Neither those nor other constant voltage in the network has ever measured !!! Therefore, all these statements are absolutely worthless, because in fact, it can be so, and then, and generally on the third!
I myself always adhered to moderate views and believed that if there is something in the network, it is not very scary. High-frequency interference can penetrate through the capacitance, so you have to fight them. And low-frequency ...
But one thing is views, another is reality. So I decided to take and make sure who is right and what is happening in the network. I did not meet special research on this topic, in addition, I am very interested in the state of the network not somewhere out there, but at my home. Therefore, I decided to investigate everything myself, especially since I have such an opportunity.
A couple of times, I already monitored the constant in the network. I collected the mockups of the measuring circuits, connected the switch voltmeter and watched it visually. And I did not see anything criminal. But this method is not very effective: in its idea the network is ideal, and if something happens in it, then this is more an exception than the rule. If you follow the arrow all day, then maybe you'll notice something (if that's the day there will be problems). But it does not go all day staring at the shooter. In addition, a large time constant of this measuring system (about a minute) is useful for measuring the "constant" constant, but when measuring a constant, from time to time, there is an appreciable error.
Not so long ago I changed the measuring equipment park, and it became possible to automatically register the measured value for a long time with a small amount of
http://www.electroclub.info/article/dc-in-220_0_files/fig3.gif
?????????? ?????????? ? ????
He is asked:
"Why are you clapping your hands?"
"I'm killing crocodiles!"
"There are not any crocodiles!"
"That's because I broke them up!"
Old anecdote
The anecdote given in the epigraph very well reflects the situation with the constant in the network. All with it successfully struggle. Internet forums are full of stories about how the equipment sounded better after installing a filter that eliminates the constant voltage in the network. Only here the idyll spoil three tiny moments:
The danger of constant in the network for transformers is declared speculatively. How much this all worsens the work in reality - I have never met such research.
Half of the schemes proposed to eliminate the DC voltage from the network, in fact, do not, and some of the most unfortunate schemes also add interference.
None of those who removed the constant voltage in the network and immediately so well heard the improvement of sound, this is the most constant voltage in the network did not measure at all! And absolutely not in the know - it was there, or it was not at all! Nevertheless, the constant of type successfully deleted and the sound improved.
In general, the dispersal of crocodiles is very successful.
There are many people convinced that the devices included in the network need to be protected from constant voltage. And from a number of other things present in it besides the voltage of 220 volts 50 hertz. They are supported by sellers of expensive (at least $ 1000) devices, called air conditioners.
There are also a lot of people who think that all this is garbage - all the devices included in the network, perfectly work and without network air conditioners. Even high-voltage interference is not very terrible - in the extreme case, the varistor has been installed, and all the cases. Moreover, there are certain GOSTs and norms for the quality of electricity, and in all our contracts with its suppliers, the compliance of energy quality with the standard is guaranteed.
Both these groups argue on Internet forums right up to swearing. Who is right?
On the one hand, the network is a very stable thing. On the way from the power station to the consumer, the current passes through a series of powerful transformers that cut off both direct current and anything that is very different from the frequency of 50 Hz. On the other hand, the transformers are not ideal (and transient processes in transformers are generally something!), And even from the transformer to the end consumer's apartment, a long wire with both resistance and inductance (and catching RF interference at the same time). And quite near, at neighbors behind a wall, any "evil" device can work. Unbalanced for both half-periods of the network, the load gives a constant component, and the transformer that can suppress it is too far away. Fantastic? And you look at the real network. Its peak factor, measured by me in several areas of my city, is somewhere around 1.35 instead of 1.41. This is because of the "cutoff" of the tops of the sinusoid by numerous power supplies. Those. the sine wave in the network looks "more flattened" than it should be. And where is the correspondence to GOSTs? By the way, transients during switching of a powerful load can be very unpleasant. In theory, the devices included in the network should not interfere with the network ... Do you believe in the idea?
But the most important thing is that all statements of both supporters and opponents are permanent in the network - they are speculative! Neither those nor other constant voltage in the network has ever measured !!! Therefore, all these statements are absolutely worthless, because in fact, it can be so, and then, and generally on the third!
I myself always adhered to moderate views and believed that if there is something in the network, it is not very scary. High-frequency interference can penetrate through the capacitance, so you have to fight them. And low-frequency ...
But one thing is views, another is reality. So I decided to take and make sure who is right and what is happening in the network. I did not meet special research on this topic, in addition, I am very interested in the state of the network not somewhere out there, but at my home. Therefore, I decided to investigate everything myself, especially since I have such an opportunity.
A couple of times, I already monitored the constant in the network. I collected the mockups of the measuring circuits, connected the switch voltmeter and watched it visually. And I did not see anything criminal. But this method is not very effective: in its idea the network is ideal, and if something happens in it, then this is more an exception than the rule. If you follow the arrow all day, then maybe you'll notice something (if that's the day there will be problems). But it does not go all day staring at the shooter. In addition, a large time constant of this measuring system (about a minute) is useful for measuring the "constant" constant, but when measuring a constant, from time to time, there is an appreciable error.
Not so long ago I changed the measuring equipment park, and it became possible to automatically register the measured value for a long time with a small amount of
http://www.electroclub.info/article/dc-in-220_0_files/fig3.gif
?????????? ?????????? ? ????
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There is a text in Russian you can try to translate in Google into any language. The sense of the article is that there is no DC constant component, but there are often various low-frequency noise due to the inclusion or disconnection of various household appliances, such as refrigerators. And the frequency of these powerful jamming can be less than 50Hz.
And this can temporarily overload the power transformers.
And this can temporarily overload the power transformers.
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This topic is not too far off.
Somebody complained about the translation (language).
This is an international forum but contributions other than in english are not allowed - too sad. For a European reader post 1 was easy to understand.
DC (called constant voltage in post 1) on the mains can cause problems. Every time you hear a toroidal transformer humming it may be some small dc component present. Good transformers do not show this effect, at least not to that extent.
So today I went to the mains outlet and checked 222 volts ac and about 20 mvolts dc. This is some 80 dB down.
It may be different somewhere else and under circumstances. Imagine a device with high power consumption like an electric oven and connected to the mains with a half wave rectifier (single diode). Result of this is a dc component on the mains (due to symmetry, conservation of energy etc).
I support the idea of monitoring the mains for effects like this. How did you do this? In addition studies should be carried out related to transformer humand about possible removal of residual dc with known "dc filters". However I disagree with assumptions about other implications to audio.
Speaking of mains filtering in general I see for instance signal transmissionfor public purposes on our mains. This is clearly audible on some mains connected devices and in poor stereo systems (especially at full hours).
My opinion has always been to build all amplifiers in a way so that they are not affected by this, but who knows ?
Somebody complained about the translation (language).
This is an international forum but contributions other than in english are not allowed - too sad. For a European reader post 1 was easy to understand.
DC (called constant voltage in post 1) on the mains can cause problems. Every time you hear a toroidal transformer humming it may be some small dc component present. Good transformers do not show this effect, at least not to that extent.
So today I went to the mains outlet and checked 222 volts ac and about 20 mvolts dc. This is some 80 dB down.
It may be different somewhere else and under circumstances. Imagine a device with high power consumption like an electric oven and connected to the mains with a half wave rectifier (single diode). Result of this is a dc component on the mains (due to symmetry, conservation of energy etc).
I support the idea of monitoring the mains for effects like this. How did you do this? In addition studies should be carried out related to transformer humand about possible removal of residual dc with known "dc filters". However I disagree with assumptions about other implications to audio.
Speaking of mains filtering in general I see for instance signal transmissionfor public purposes on our mains. This is clearly audible on some mains connected devices and in poor stereo systems (especially at full hours).
My opinion has always been to build all amplifiers in a way so that they are not affected by this, but who knows ?
I repeat, the author's conclusions, after numerous measurements made by him. In fact, there is no constant component of direct current. All changes in the sinusoid were of a temporary nature, and they could be more attributed to the imposition (modulation) of low-frequency oscillations at a carrier frequency of 50 Hz and temporal distortion of the sinusoid. Over time, the form is recovered and the process is not stationary.
I believe that the best solution is to have a large margin of inductance in the primary winding of the transformer. This will make it easy to cope with even the lowest frequencies. For a long time, similar transformers were easily implemented, for example, in the output transformers of tube amplifiers. But in order to obtain high inductance in a power transformer and at the same time to have maximum efficiency, it is more advantageous to use an amorphous core.
I believe that the best solution is to have a large margin of inductance in the primary winding of the transformer. This will make it easy to cope with even the lowest frequencies. For a long time, similar transformers were easily implemented, for example, in the output transformers of tube amplifiers. But in order to obtain high inductance in a power transformer and at the same time to have maximum efficiency, it is more advantageous to use an amorphous core.
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A) You are talking about the Utility Power network? ("Network" covers many kinds of circuits. In the US we don't always call the utility power grid a "network".)
B) The economics of electric and conductors are about the same everywhere. And have been since the 1910-1950 period when Al came into wide use. $ per conductivity, also strength-to-weight (span), Aluminum is VERY much better than Copper. The problem is poor connections on the oxide. Any run over about 30 meters is very likely to be Al, because the savings on the wire justify the added labor and Al connectors. Runs under 10 meters and 50 Amps are usually Copper for quick/economic termination.
Around 1970 the US was throwing a lot of brass into a swamp, price of Copper rose, and Aluminum was used even for short runs to wall outlets. These gave trouble within a few years, including fires. A series of upgraded wall-devices was small help. Al is still legal but nobody wants it for inside wiring.
Steel is also used. My neighbor is 200 meters from the street. My 170m Al 240V feeder sags a lot. His feeder is run at 19,000 Volts, transformer at the house. His line current for 100A in the house is like 1.2A on the 19KV feeder. Lampcord would be over-size. PC mouse cord is plenty. BUT trees fall on it. It has to be like 1/4"(6mm) steel to take wind, ice, and branches. The steel has way more conductivity than the load needs @ 19KV.
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I think that the conditions everywhere are about the same, and even in a completely different part of the world, anywhere in Japan or England may be better in the city and worse in the village or vice versa, it all depends on the specific place. But it can be quite accurately seen that all the time engineering thought received great resistance in the field of economics and financing. For example, expensive but also technically advanced transformers on amorphous cores for distribution networks have received the greatest distribution only in China and in Japan.
I mean home wiring from a wall outlet to the nearest distribution transformer. In apartment buildings, household electrical wiring is made of aluminum. It is possible that the cable is made of copper from a switchboard into a distribution transformer. But often the windings of the distribution transformer again consist of aluminum, although at present, for example, in Russia there is a tendency to replace aluminum with copper. But I saw completely new research in the US where scientists again recommend replacing copper in transformers with aluminum, but at the same time partially compensating for large specific losses due to the use of flat aluminum tape. This is to quickly pay off in the price now, instead of saving energy in the distant future.
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According to the definition in decibels (dB) you can not compare two completely different types of voltages, as in your example - AC with DC.
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