Ok , didnt caught that part on the thread , but it s really not
a good idea as well as the OP proposition.
Best would be to look at if the transformers have a 220V winding ,
wich would be logic for a japanese export model , and if there s none,
simply swapping them with 220V models..
Doing otherwise is just asking for a lot of trouble...
I figured that!
But after all this nonsense I am almost hoping he tries it!
I'm not sure it is worth trying to argue this point, as anything I say may be dismissed as 'speculation' or 'theory'. Let's not get into a silly argument about the semantics of what is AC or DC. That old thread never made any real progress.
Half-wave rectified mains will include a frequency component which is almost equal to 0Hz (gets closer to 0Hz the longer you leave it switched on) so will see only the transformer primary resistance. If you don't believe me then do the Fourier analysis yourself (you do know how to do Fourier, don't you?). There will be a big current, and you will cook your transformer as it behaves more like an electromagnet.
Alternatively, solve the differential equation for L+R in series with an applied voltage given by half-wave rectification. This is much safer than doing the experiment. It might even lead to understanding.
Half-wave rectified mains will include a frequency component which is almost equal to 0Hz (gets closer to 0Hz the longer you leave it switched on) so will see only the transformer primary resistance. If you don't believe me then do the Fourier analysis yourself (you do know how to do Fourier, don't you?). There will be a big current, and you will cook your transformer as it behaves more like an electromagnet.
Alternatively, solve the differential equation for L+R in series with an applied voltage given by half-wave rectification. This is much safer than doing the experiment. It might even lead to understanding.
I think you misunderstand the goal! It is to prove that ... is right no matter how silly or stupid it gets!
As to a "Magnetic Field Amplifier" that was just covered by the mention of the triac RMS reducer. It reduces RMS voltage but the peak stays the same. It decrease the amount of time the current is flowing therefore less core iron is needed. It plays havoc with power generation so is not permitted anywhere with even modest regulations.
DF96, a 10mS signal cannot be zero hertz the conversion is 1/T and it is only one half, thus the frequency is 50 hertz and the period is 20mS, far from (0Hz) DC anything, the primary resistance of the transformer does hardly play any role at all.
You can do as many fourier transforms as you like all you will see is harmonics and they will be odd let me assure you.
We made transformers for the past 50 years I only proposed the solution because 1) it is simple; 2) it works 3) there is no danger in damaging the transformer and 4) it is the most simple way to half a 220VAC supply.
In my humble opinion, our friend can run his amps using this method for as long as he likes without any problem at the cost of two 10 amp rectifier diodes a fraction of the cost of a step down transformer.
You can do as many fourier transforms as you like all you will see is harmonics and they will be odd let me assure you.
We made transformers for the past 50 years I only proposed the solution because 1) it is simple; 2) it works 3) there is no danger in damaging the transformer and 4) it is the most simple way to half a 220VAC supply.
In my humble opinion, our friend can run his amps using this method for as long as he likes without any problem at the cost of two 10 amp rectifier diodes a fraction of the cost of a step down transformer.
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If one looked at the waveform it became a series of high spikes probably from the diode switching and the inductance of the winding it did not resemble a sine wave at all but more a triangular wave with a huge spike at the onset of every cycle. The secondary rectified voltage jumped up by about four times instead of halving as I was expecting.
There you have it, practical test is what counts. I simulated this but got a completely different result from what happens in practice.
Nico
There you have it, practical test is what counts. I simulated this but got a completely different result from what happens in practice.
Nico
Interesting! I for one ain't gonna rag on you for arguing the point. The OP had his answer some pages back; we're just having some tech fun.
If the spikes aren't from the diodes, it'd have to be kickback from the primary. That would explain the secondary jump, too. I've no idea for the triangular wave.
That right there is good enough reason for anyone reading this to never subject your amplifier to this kind of abuse.
If the spikes aren't from the diodes, it'd have to be kickback from the primary. That would explain the secondary jump, too. I've no idea for the triangular wave.
And Pease is smiling.
No Wahab,
I used* one of our 500VA toroidal transformers. While the secondary is open circuit the waveform seems fine, it looks like a bad half wave rectified signal, even the bottom part is rounded and not flat.
As soon as one places a load on it, I used 2 amp then the wave form changes very abruptly, to become a spiked sawtooth/triangular waveform and the transformer buzzes and it gets very, very hot in a short period of time.
Anyway it was an interesting test.
I used* one of our 500VA toroidal transformers. While the secondary is open circuit the waveform seems fine, it looks like a bad half wave rectified signal, even the bottom part is rounded and not flat.
As soon as one places a load on it, I used 2 amp then the wave form changes very abruptly, to become a spiked sawtooth/triangular waveform and the transformer buzzes and it gets very, very hot in a short period of time.
Anyway it was an interesting test.
This thread would be incomplete without the mad hatter's contribution (tested though):
http://www.diyaudio.com/forums/powe...-elegant-insane-way-converting-220v-110v.html
http://www.diyaudio.com/forums/powe...-elegant-insane-way-converting-220v-110v.html
That is the basis of the "Magnetic Field Amplifier!"
Not a good technique to use before a power transformer, but it is very useful after one! The peak of the AC line voltage gets squashed by all the linear power supplies, so just grabbing current on each side of the peak gives a semi-regulated voltage. It also helps improve power factor of the entire AC power system!
Correction: DC, fundamental, and even harmonics only. Sorry.DF96 said:
Further correction: I was thinking of a voltage source, with output voltage equal to half-wave rectified AC. This is incorrect, as whenever the diode switches off the source becomes effectively open-circuit. In addition, the transformer (if unloaded) will act like an inductance and will try to maintain conduction even when the diode would have switched off with a resistive load. The result will be much less current than I originally predicted. This mechanism will fail if the transformer is loaded, as Nico found out.
So it looks like we were both wrong. Apologies.
Audiofan that's what I'm trying to make for my next AMP, please tell me it's possible.
Yes that works, but better is two secondary coils. A pretty standard arrangement. Look at any transformer catalog.
Be very carefull if you work with this circuit, transformer phasing is tricky ...... if you need more advice I may give more information and more theory .......
In this circuit both secondaries are parallel so they have same voltage, then refected voltage on primaries mus be equal too
To make it work induced voltage must be in phase from one transformer to the other ..... to get this there is a few test must be done ...... you will need only a voltmeter and a lightbulb ..... and some ..... know-how
In this circuit both secondaries are parallel so they have same voltage, then refected voltage on primaries mus be equal too
To make it work induced voltage must be in phase from one transformer to the other ..... to get this there is a few test must be done ...... you will need only a voltmeter and a lightbulb ..... and some ..... know-how
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