| Electronics > Beginners |
| nobody talking about switching PS wasting power on input filter caps? |
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| soldar:
There is so much confusion in this thread. radiolistener, you are not listening. Assume an AC generator directly connected to a resistor. The power supplied is in phase with the voltage. Now we connect a capacitor in parallel with the resistor. During the first quarter cycle the generator has to work harder because, besides the power being supplied to the resistor it is also charging the capacitor storing energy in it. It is working double time. During the second quarter cycle the capacitor is returning the energy which goes into the resistor and this means the generator has to work less. Whatever current is supplied by the capacitor is less current the generator needs to supply. If you do not understand this you should not continue to argue. You should go back and study some more until you understand it. |
| capt bullshot:
--- Quote from: radiolistener on August 25, 2019, 01:34:58 am ---Updated: I have thought and it looks that I was not right, we cannot compare short circuit with large capacitor. These things with AC alternator looks very strange, needs to learn it more deep and make some experiments :) --- End quote --- In terse: Your general AC generator / motor (in German EE we don't use these terms, we just say AC Machine or Engine, regardless of whether it is used as Generator or Motor), will act as an inductor if you load it with an capacitor and vice versa. So the energy that is "consumed" back by the generator from the capacitor isn't consumed but stored in that inductor and than delivered back to the capacitor in the next cycle. Think of an LC tank, works the same way as one compensates inductive load by using capacitors. The amount of inductance or capacitance that the generators shows to deal with its load is determined by that nice term "Polradwinkel" (angular displacement in synchronous generators) - one can set this either by changing the excitation of the generator (think of power plants) or it just works implicit (think of small generators / motors). And yes, if there weren't losses, a generator loaded by a capacitor would run infinitely, same as an unloaded generator would do. The capacitor doesn't make the generator run forever, slower or faster, indeed it wouldn't change anything (in the ideal lossless model). |
| soldar:
People with a poor grasp of things tend to confuse concepts and there is where we end up with people saying they think they have found a free energy source. Saying perpetual motion is not possible is only a way of saying any machine we build in reality is going to have losses. But ideally perpetual motion is possible and we can see examples which get pretty close. The planets have been revolving around the Sun for some time now and will continue to do it for the foreseeable future. What is impossible is not "perpetual motion", what is impossible is any system which yields more energy than it has stored and is receiving. Energy cannot be created out of nothing. An ideal machine can only yield as much energy as it is receiving. It can store it, it can transform it but it cannot create it. You cannot get energy out of nowhere. With an ideal inductor and an ideal capacitor we could build a resonant LC circuit which would resonate forever but we could not extract energy from that system without slowing it down. You can imagine an ideal pendulum which will oscillate forever but you cannot extract any energy without slowing it down. The amount of energy you can extract rom any system is what was put into it in the first place. No more. |
| emece67:
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| radiolistener:
--- Quote from: emece67 on August 25, 2019, 10:46:07 am ---More nonsense, now the impedances vary with time :palm: --- End quote --- :palm: Don't confuse "time delay" with "time". This is different things. |
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