Newsgroups: alt.engineering.electrical, rec.audio.tech, sci.electronics.misc, sci.engr.electrical.compliance Subject: How HUMplug-e ground loop solver works ? Anyone has experience on this HUMplug-e product ? Web page http://www.21best.com/21_best/electronic/security/video/filters/for_sale_.html says: " Simply plug your equipment through this, to cure it of Ground Loops. Filters out unwanted voltage and current in the ground line that cause ground loop hum while simultaneously maintaining a solid, safe ground." I have experience on many different way on solving ground loop loop problems in audio/vidoe systems. Practically every other types of products listed on that page are known to me in details (I have used similar produicts, know what is inside such items, even manufactured some quite simlar products). I have written some material on ground loop solving to http://www.epanorama.net/documents/groundloop/index.html How this HUMplug-e product works makes me wonder. Given the specifications (15A current) and a small size it can't be an isolation transformer. According the description it keeps the solid ground connection it just can't be a "cheater" plugs that just simply cuts ground connection (dangerous peactice that is not recommended). My quess that it does some magic on ground connection so that it stops/reduces the current that can flow on normal ground loop case, but still lets the ground connection to be good enough for electrical safely. I am just wondering how this is done in such what that it works and meets the electrical code safey requirements. Anyone has experience on how this is implemented ? Some of my quesses would be those impklementation possibilities: - some common mode coil type construction over all wires - two parallel diodes (on different directions) wired between input and output ground connections (stops current when voltage difference is low but will pass hort circuitfualt currents at low voltage drop) Anyone commenting my quesses how this device works ? Anyone has experience on this ? One quess is that this HUMplug-e could be based on circuit similar to Figure 3 - A High Current Safety Loop Breaker Circuit at web page http://sound.westhost.com/earthing.htm Description of the web page: "The loop breaker works by adding a resistance in the earth return circuit. This reduces circulating loop currents to a very small value, and thus breaks the loop. The capacitor in parallel ensures that the electronics are connected to the chassis for radio frequency signals, and helps to prevent radio frequency interference. Finally, the diode bridge provides the path for fault currents. The use of a large chassis mounting (35A) type is suggested, since this will be able to handle the possibly very high fault currents that may occur without becoming open circuit. Note the way the bridge is wired, with the two AC terminals shorted, and the two DC terminals shorted. Other connection possibilities are dangerous, and must be avoided." "In the event of a major fault, one (or more) of the diodes in the bridge will possibly fail. Semiconductors (nearly) always fail as short circuit, and only become open circuited if the fault current continues and 'blows' the interconnecting wires. High current bridge rectifiers have very solid conductors throughout, and open circuit diodes are very rare (I have never seen a high power bridge go open circuit - so far at least). Use of the bridge means that there are two diodes in parallel for fault current of either polarity, so the likelihood of failure (to protect) is very small indeed." This circuit installs a circuit consisting of diodes, resistor and capacitor the grounding wire. Would using this kind of circuit on groudn path be electrically safe and/or legal in this kind of application ? -- Tomi Engdahl (http://www.iki.fi/then/) Take a look at my electronics web links and documents at http://www.epanorama.net/
