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In Reply to: This is not what you want at all posted by Russ57 on June 24, 2004 at 09:14:28:
it is an inductance set across the line to be used as energy storage and a sort of poor-mans power-factor correction. Any filtering, I think, has to come from the capacitance in the windings; that is it is a byproduct and not an intended consequence.Where it seems to help is in keeping the current wave-form properly in place relative to the voltage one. It also does ABSORB surges from the line if they are quick enough (so does your regrigerator when it is running). Strangely enough, MOV's anywhere in the house also absorb and damp spikes.
This is not a replacement for JR's filter, but rather an adjunct to it.
Give Me Ambiguity or Give Me Something Else!
Follow Ups:
I suggest you read Al's post above as I think you are mistaken about the nature of the voltage/current relationship in the face of a highly inductive or capacitance load. In fact the current will lag or lead and not be kept in "proper relationship" relative to the voltage.
Russ
If you apply the voltage to an inductor, when you remove the power you will get the back emf in hundred of volts, so when you switch off the big inductive load it will dump big voltage spike back into the power line that is why they install a snubber cirsuit across the switch that is used for turning on and off the inductive load. It is no secret of the RG demonstrating the light bulb trick. If you measure the capacitance of the GR unit beween the ground pin and thw hot and neutral you will read about 0.001 uf which what is actually doing the filtering due to the stray capacitance of the tranformer. Just remember one thing, high frequency see inductor as a high resistance so if you want to filter out high frequency you put it in series, you put capacitor in pararell with the load to filter out high frequency.
componants in an AC circuit is to use their phase shifting to correct for the phase shifting caused by other reactive loads in the system. For instance capacitor banks are often used in factories to counter the phase shift caused by motors. So, in that sense, the reactive componant DOES keep "phase and voltage in proper relationship" as I wrote. It is the end result, not what the device in question technically does individually.Now, as to whether or not an inductor ACROSS the line corrects for phase shift caused by devices that draw a load inductively (as do some amplifiers under heavy load) is another question entirerly. The Richard Gray company seems to think so as do some happy users.
And contrary to Al's statement of "a few milliwatts" their demos at shows has them holding light bulbs on for quite a bit more than a second after power removal. (Low voltage ones, for safety I presume.)
Give Me Ambiguity or Give Me Something Else!
Mike is correct that large industrial users apply banks of capacitors to their power grids to counteract the effect of heavy motors on the load they present to power suppliers. In these cases, the motors are on most of the time, and it is sensible to permanently connect the capacitors.The power utilities do not like the waste of energy (from I^2*R losses) in their equipment from reactive current drawn by the industrial users, so they have requirements for limits to the amount of inductance relative to the resistive loads. These are expressed as Power Factor, defined as the cosine of the phase angle between the voltage and current wave forms. For a purely inductive load, the PF is 0. For a purely resistive load, the PF is 1. For loads with some inductance and some resistance, the PF is a number between 0 and 1. Since the utility has to size its equipment for the peak current, even if the peak current is larger than that which produces power at the customer's site, they want the PF to be as close to 1 as possible. The power factor at most residential users is close enough to 1 to not be a problem.
The Richard Gray site implies that adding their device somehow corrects for inductive loads elsewhere in the house, such as refrigerator motors. This is correct, as the parallel combination formula for non-interacting inductors is the same as for parallel resistors and series capacitors: 1/Lt = 1/L1 + 1/L2 +... However, it does not seem to be an issue with the power utility, and I doubt it affects audio equipment. The non-audio loads may generate noise and create other problems, but the inductance is small. Since the refrigerator motor cycles on and off, leaving the RGPC choke connected permanently results in over-correction when the motor happens to be off.
Note that my calculations (for milliAMPS, not milliwatts) were for the 5 henry choke proposed by the DIY site. I don't know how large the RGPC choke is. Any shunting of high-frequency noise on the power line would have to be through the stray capacitance of the choke winding, as a good choke looks like an open-circuit to a high-frequency signal. If the choke has a low DC winding resistance, it will act to remove the DC component of any power voltage distortion caused by other equipment. This is helpful to audio equipment with toroidal power transformers, as these can be saturated easily by DC on the power line.
However, the demonstration trick of keeping a light bulb illuminated upon power interruption is misleading. The choke stores and releases energy in its magnetic field, which is fluctuating along with the current wave form. A brief (much less than one power cycle) interruption can take place at any time during the power cycle, so it is impossible to predict how much magnetic field energy will be on hand in the choke when the interruption occurs, and how much of a voltage spike the choke will apply to the parallel-connected audio equipment.
does the fact that the capacitance is distributed throughout the entire winding give the "capaicitor" more current carrying capability than the standard ac filter cap?And Al is right, power factor correction is not just throwing reactive componants into the a/c line willy-nilly; these things are carefully planned out in industrial useage.
I totally missed the action on the dc that may be in the power line; refrigerators compressor motors would love that. May be the best use for the device!
I did question the guy doing the demo as to how that current that was keeping the low voltage lights lit was supposed to help an amp drawing a burst of 20 amps. I don't recall a good answer.
I have been told by another guy that opens things up that the bigger gray units are just stacked single units. And users of Gray's device do point out that there is a point where adding units no longer helps, but rather hurts, the sound. So there is obviously a point where overcorrection does occur.
Give Me Ambiguity or Give Me Something Else!
> does the fact that the capacitance is distributed throughout the entire winding give the "capaicitor" more current carrying capability than the standard ac filter cap?Yes, and it makes it much more robust and linear at lower noise voltages. Perhaps this is the secret to its success.
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