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In Reply to: RE: Some simple facts posted by Jon Risch on August 08, 2014 at 23:14:50
Same as your design but say 100 to 120 watts. See any problem or reason not to?? I just met someone who described a filter that took 120 up to 240 and then down. The opposite ?? If you think this is a good idea( whole system) can you suggest the trannies? Thanks, Tweaker
Follow Ups:
1st, 100-120W is not enough to adequately run an entire system. There is some losses with the down and up conversion of the voltage, so if you had 100W units, and a filter cap in between the two transformers, you might only end up with a total capacity without significant line droop of 80 w.
Even a HTIB would need more power than that to operate properly on peak output.
2nd, my original design was stepping down the voltage so that a relatively massive amount of capacitance could be placed across the line for filtering, and yet avoid the usual penalty of a lot of leakage current being present due to the cap.
Stepping up the voltage would require a higher voltage rating cap, and provide less safety margin for that cap.
Step down transformers are much more readily available, and much easier to wire up safely, etc.
If one were to try to take this simple quick and dirty technique to it's maximum capability, then a pair of one to one (120vac IN, 120vac OUT) E-I core power transformers with a rating of 15 amps at 120VAC would be the way to go, or perhaps as a close second, a pair if identical 500 to 800 watt rated transformers with a 50-60 VAC secondary would be OK. How OK would depend on the exact details of your system with regard to the power demands and requirements of the total sum of the equipment.
Neither one of these would be a cheap purchase, and with such large units, there would need to be adequate distance between the two transformers so there was no magnetic coupling between the two. I would say with proper orientation, they would need to be at least 6-8" apart.
Jon Risch
The caps are one coil away from the ac source so do these filter at all at the ac source?? Tweaker
The main idea of this type of filter, is to isolate the load from the line, and the line (and everything else on it) from the load.
What you are asking is, does the filter provide any filtering directly to the AC line, therefore providing some benefit to other loads on the AC line.
The answer is yes, sort of. And, it depends.
One reason I use EI core transformers, is that they tend to filter out higher frequencies on the AC line, and this works well towards the original goal of this type of filter. However, it also makes the capacitance that is placed across the secondary less effective, because it is not coupled back onto the AC line as well.
So the more HF losses the transformer has, the less effective the capacitance will be in terms of directly filtering the AC line itself.
Just remember, that once you start placing capacitors directly across the AC line, that once a certain size is reached, you have exceeded the allowable leakage current according to the various Safety Agencies.
This leakage current can trip GFI type outlets, which at the least, is a nuisance and bother.
The capacitance that will cause the leakage current limits to be exceeded is not that great, just a small fraction of a uF.
Jon Risch
Dosn't the step down feature have something to due with it's filtering? Maybe not if you think equal transformers will work. Lots of caps is a very good feature. Can you hear these small transformers buzz from more than a few feet away?? Tweaker
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