AC motor questions

[nueview]

love what you just showed i have seen this used for motor demonstrations before they are simple and yet quite elligent but not real practicle but they do work perhaps something is missing in our understanding about this phenominas possible uses for motive power.

[Charlie_V]

Thank you. Is there any reason why we can't use two generators to sent then same frequency and phase currents into transformer and output from the transformer feed back as a replacement for one of those generators  ? That way one of the generators is needed only at start and such transformer will continuously output current of bigger and bigger voltage or amperage probably up to damage or core saturation .
Does it makes sense ?

I think I see what your saying.  A transformer only converts voltage to current or current to voltage, the power or energy in the transformer is the same (Power = Voltage x Current).  So you can take 50 Watts of power and produce 5000 Volts but the maximum current your load can draw would be 0.01 Amps.  If your load requires more current than that (i.e. your load is a very small resistance), the power source will not be able to supply it and the voltage in the transformer will begin to drop.  Likewise, with 50 Watts you can transform the voltage to 0.005V and the current available will be 10,000 Amps.  Of course you'd need very thick wires of very low resistance to handle that much current without over heating and melting the transformer's wire - your load would need to be a very low resistance too). 

So getting back to your question, two generators hooked to one transformer will just double the amount of power that a single generator could produce.  The transformer does not create energy, it is only a pressure/flow converter.  So feeding back the output of the transformer even if it is high voltage, will not be able to take the place of a generator.  This is mainly because the losses in the system bring the operation down to below 100%.  If you had 100%, then no loss would be in the generator, and you could close the loop as long as you didn't pull any energy from the system. 

Sorry this is a little confusing to grasp at first.  The REAL reason as to why the transformer cannot be fed back is because of something called Lenz's Law.  All that means is that the output coil of the transformer tries to oppose the input coil.  So if the input coil is generating a north pole, the output coil ALSO generates a north pole, so that the flux within the transformer cancels - please be aware that this ONLY happens when there is a load on the output circuit; without a load no magnetic field is generated in the output coil, only a voltage.  The output coil tries to match the exact magnetic field value as the input coil (only because of losses it is always slightly less in value than the input).  That way, the power delivered to the output circuit is slightly smaller than the input circuit - does this make sense?  The exact same effect is also found in motors/generators as well.  Only in those machines, the input coils try to stop the rotor from moving - but its the same effect, they are trying to cancel the changing magnetic field of the output - whether the output's changing magnetic field comes from a coil or a rotating permanent magnet.  Many people, including myself, are looking for ways to fool the output circuit so that it reacts to a bigger change than what it sees, or that its reaction cannot affect the input - I've had some success with the later, but no O.U. as of yet. 

Charlie

[nueview]

charlie

if you put capacirors across the primary of the transformer so it becomes a tank circuit drawing current off the secondery will alter the inductance of the primary and allow more current to flow from it to the secondary but if the frequency floots up at the same time what would be the end result. is current then proportional or not any ideas on this at all.

martin

[forest]

I think I see what your saying.  A transformer only converts voltage to current or current to voltage, the power or energy in the transformer is the same (Power = Voltage x Current).  So you can take 50 Watts of power and produce 5000 Volts but the maximum current your load can draw would be 0.01 Amps.  If your load requires more current than that (i.e. your load is a very small resistance), the power source will not be able to supply it and the voltage in the transformer will begin to drop.  Likewise, with 50 Watts you can transform the voltage to 0.005V and the current available will be 10,000 Amps.  Of course you'd need very thick wires of very low resistance to handle that much current without over heating and melting the transformer's wire - your load would need to be a very low resistance too). 

So getting back to your question, two generators hooked to one transformer will just double the amount of power that a single generator could produce.  The transformer does not create energy, it is only a pressure/flow converter.  So feeding back the output of the transformer even if it is high voltage, will not be able to take the place of a generator.  This is mainly because the losses in the system bring the operation down to below 100%.  If you had 100%, then no loss would be in the generator, and you could close the loop as long as you didn't pull any energy from the system. 

Sorry this is a little confusing to grasp at first.  The REAL reason as to why the transformer cannot be fed back is because of something called Lenz's Law.  All that means is that the output coil of the transformer tries to oppose the input coil.  So if the input coil is generating a north pole, the output coil ALSO generates a north pole, so that the flux within the transformer cancels - please be aware that this ONLY happens when there is a load on the output circuit; without a load no magnetic field is generated in the output coil, only a voltage.  The output coil tries to match the exact magnetic field value as the input coil (only because of losses it is always slightly less in value than the input).  That way, the power delivered to the output circuit is slightly smaller than the input circuit - does this make sense?  The exact same effect is also found in motors/generators as well.  Only in those machines, the input coils try to stop the rotor from moving - but its the same effect, they are trying to cancel the changing magnetic field of the output - whether the output's changing magnetic field comes from a coil or a rotating permanent magnet.  Many people, including myself, are looking for ways to fool the output circuit so that it reacts to a bigger change than what it sees, or that its reaction cannot affect the input - I've had some success with the later, but no O.U. as of yet. 

Charlie

Thank you. Let's summarize. Is Lenz's law the only reason (beside of resistance of wires) that we cannot feed output current back to the primary  ?
I think we should follow open mind path of investigation: instead of quote exact law, we should point what would happen if we have a way to exclude the effects of such law.
What else we need to overcome , to feed back output current from transformer to the input ? I can only imagine that  we should work out some overrun protection to limit accumulated current/voltage rise cause by positive feedback and influence on generator (or a way to remove even that single generator which is left)

Current situation:

1. We have two generators outputting exactly the same AC current into transformer . This is easily done.
2. We have to invent a way to eliminate or restrict Lenz law effects
3. We then feed back output current into primary and turn off one of the generator while protecting the other from this back current (somehow I feel that this current may look at generator as a path to ground with less resistance then a transformer)
I have a feeling also that this output current should be maybe "prepared" to match phase and frequency of input ? Am I wrong ?
4. The result is TWICE the power at output of transformer compared to the input from  generator (second generator is needed only for start)  AT EACH turn of feedback. Soon it will destroy transformer or generator.

I'm strongly convinced that such positive feedback is something we were learned to eliminate but it's the way to OU obviously.

Now it's time to point any flaws in that argumentation... Could you also tell me something about Lenz's law ? I'm interested if this is electric or magnetic effect : in other words what is opposed FIRST, what is the origin or this law, and if this is principle law or just a rule from experiments. I will try to read about it but I'd like to know your opinions.

[Charlie_V]

@nueview

Adding capacitors can do a number of interesting things.  Mainly, it will be like adding a filter.  Basically if your input Ac frequency does not match the resonance of the secondary, the secondary will weed it out and you won't see much on the other side.  That of course is only half the story.  Because if you match the secondary resonant frequency to the AC input of the primary, you still may not get REAL power (in the sense that the voltage and current in the secondary can be out of phase if the values of your secondary inductance and capacitance do not equal (or the ratio does not equal) that of the primary circuit.)

@forest

To my knowledge Lenz's Law is the ONLY thing restricting it.  Sure resistance will too, but if lenz's law didn't exist then the resistance would have to be REALLY big to stop the feed back.  Personally, I don't like to refer to the effect as a law because it makes it sound like nature is following a "law" of man - when in reality its the man made "law" that follows nature. 

All it means is that when a coil sees a changing magnetic field, it tries stop the change by countering it with its own magnetic field.  So if a north pole approaches a coil, and the coil is shorted (i.e. Loaded) the coil will generate a north pole that tries to push the approaching magnet away (or slow the approaching north pole down).  Likewise, if it was an approaching south pole, the coil would generate a south pole.  If a north pole tries to move away from the coil, the coil will generate a south pole and try to pull it back.  So if a magnet is rotated near a loaded coil, the coil will try to slow its rotation - this is what lenz's law describes.  If there is no load on the coil (the coil is open circuit), only a voltage develops.  The coil will not produce an opposing magnetic field because current can not flow in the coil due to it being an open circuit.  But the sign of the voltage will show you which way the current will flow when loaded.  And the current always flows in a direction to create an opposing magnetic field. 

The best way to understand it is to FEEL it for yourself.  Take a thick aluminum or copper ring (hard drives have them or you can make it out of wire) just a donut of metal really.  Then get yourself a very strong rare earth magnet.  Now move either the magnet or the ring so that the magnet goes through the center of the ring.  You'll feel a force that pushes against the moving coil/magnet as it approaches, and pulls it back as it leaves.   Make sure the magnet is either much larger than the ring, or the magnet fits perfect inside the ring.  If its a really tiny magnet, or if the ring is too small, you won't feel the force. 

Once you can find a way around this effect, then you'll have to worry about feed back problems.  Until then, don't sweat it 

Charlie