14. Mains Cleaning transformers
There are a few good reasons to use a mains cleaning transformer, or a Lundahl Mains transformer which all have the same construction. The quality of the mains voltage is reducing every year, and I think we have not reached the worst point yet. I remember at what high quality level we once were. My grandfather had an electrical clock, that he build himself. A so called synchronized clock. It has a very small electric motor, of the kind that is in phase with the mains. So it was extremely accurate, and as a kid we were admiring the old man for building it. Even so, at the electricity plant, they used a similar type clock, and they would adjust the mains frequency by hand, such that their own clock was accurate up to the second, and then so were all other clocks in town. Mind you, that was in the days of coal fired electricity plants, controlled by hand, and electronics if at all, was with electron tubes. That could be done close to perfection.
Today such a clock would still work, but it would be inaccurate, because of the short electricity break downs, which have become so common. During those seconds or minutes, synchronous clock would not run, and electricity companies just don't care any more. Together with that comes the wild fluctuations in mains voltage, and wave shape distortion. The overall result is not very good.
We see now the governments step out of electricity distribution and leave this to the private economy. As a result, private electricity companies separate the things that make money, from the things that cost money. They make money with selling electricity for a higher price as they payed for it. What only costs money, is maintenance of the cable network. Things like preventive maintenance and prepare a cable network for the future, is avoided as good as they can. They just work around the shortcomings. The network detoriates every year, and can not handle a peak capacity any more. This tendency to lead electricity from everywhere to anywhere can also cause a full collapse, and a whole state like California had no electricity, also in New York and Munich it recently happened, and that was not bad luck. That was bad network condition. Also start up a collapsed network is very troublesome.
Most users will not be able to easily to measure mains voltage distortion, but If you just take a voltmeter, and measure your house voltage sometimes, you will see the problem. Wave shape distortion is a problem for specific equipment, like a direct drive record player. Or, if you ever wondered why an AC tube tester doesn't test the same tune with the same result, even though the mains voltage was adjusted properly, that is because of wave shape distortion. Even some older tube test manuals warn for this, but that was in the 1950's when Wave shape distortion was only a fraction of what it is today.
The city cable network, the grid, is simply as overloaded as far as possible, to avoid costs. So there is a large voltage drop at the moments when everybody is using electricity, and no solar energy pumped into the network. That will be mainly when it is dark outside, and people are at home. On the other hand, there are moments in shiny mornings, with little energy use, causing too much production of private solar energy. For the electricity companies this a problem, because they are obliged to accept the solar energy, but they have nobody to give it to, and very few can store such massive amounts. So on purpose, they let the voltage rise, and if it rises 5%, they just let your home equipment use 5% more energy. If that doesn't help, they have the so called "solution", of negative energy prices. That means they are paying some specific users to accept energy, as this is the only thing they can do at such a moment. When solar panels pump 1 Megawatt into a specific area, wheras the use is only 0.8 Megawatt, they have to get rid of 0.2 Megawatt. (and if they don't the mains voltage would rise above maximum). It makes no sense to transport the energy to the next city, as they have the same problem at the same time. The only way to get rid of energy is: electric heating of something. For instance "sell" the energy for negative price to companies who have huge heating ovens. These run for no use, just to get money for it. The financial mechanism for this is the electricity market. So when market prices get negative, it means you can make money by destroying electricity. Even so, some very modern solar panels can be reversed, meaning they can be used to heat up the panels, destroying energy, which they get payed for. A very crazy situation, but it is what we have. Home battery systems are a good way out of this dilemma, but prices of those are still too high. So far for the voltage fluctuations. At such moments of voltage rise, all electronic regulated power supplies begin to phase cut the mains voltage mire sharply, causing more distortion.
Another problem, is modern electronics that regulate the power supply. So yes it was well understood by equipment builders, that the mains voltage is very instable. They add regulating electronics inside their equipment. However the way such electronic circuits load the mains, is not a nice one. These are phase cutting electronics, such as triacs. At slightest mismatch, these can leave a residual DC voltage on the mains, by lifting off the neutral against ground. You can try this out yourself. Just let a normal incandescent bulb burn on half the power, by putting a power diode in series. You pull DC current now from an AC network, and so you are lifting up the neutral line, and that will give more mains hum on any mains transformer without air gap. That is not much, just a Volt or so, or less, but effects in equipment transformers is there, when they are not made for this.
Phase cutting is always done, when there is a LOT of power involved. Like in washing machines or air conditioning motors, or heavy machinery of a company a few blocks away from your house. All of this makes the mains voltage dirty.
Here is another modern problem: For small equipment, there are circuits that rectify the mains voltage directly, and feed this into DC to DC converters. These have a charge pumping effect. So the mains is loaded in "spikes" into a capacitor, and the sine wave gets distorted from this. Such are those typical mains plug power supplies, which are connected to the outlet even without a cable, but also internal PC power supplies work like that, and in every household can be found dozens of such devices.
Something which lifts up the neutral (so not the ground) is unevenly loading of the three phase power network. Specially when this is done by phase cutting electronics, the risk of a small DC component becomes realistic.
Please check the pdf file below, to read more about it. I see sometimes often people spend a fortune on Voodoo mains cables, with "specially treated" materials, and whatever. I understand people have a problem, and seek a way to get rid of all the noise and disturbances, but I don't think any "cryogenically treated" copper is going to do that for you.
The Lundahl company since many years has a a few mains cleaning transformers in the program, using a core with air gap, which gives a transformer the capability to withstand a small DC component. A very typical air gap product is a power supply choke of course, as it carries more DC than AC. However an air gap can be extremely beneficial nowadays, to filter the mains voltage.
The most recommended mains cleaning transformer is LL1662. This transformer can also increase or reduce the mains voltage is needed. So when you have 238.. 248 Volts all of the time, you may want to wire it for 5% voltage reduction, and of course get the filtering function still.
Please click on these pictures to see my recommended way to connect LL1662 .
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(Last updated: 11-May-2018 9:38 )