Electrical code Compliance - How HUMplug-e ground loop solver works ?

Author

How HUMplug-e ground loop solver works ?

Tomi Holger Engdahl

2007-06-12, 9:25 am

Anyone has experience on this HUMplug-e product ?

Web page
http://www.21best.com/21_best/elect.../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/...loop/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/

Benj

2007-06-12, 1:25 pm

Tomi Holger Engdahl wrote:
> Anyone has experience on this HUMplug-e product ?

No but is sounds as if the HUMplug has a circuit similar to the one
you found...except it may have a 15 amp bridge rather than a 35 amp
one.

> 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 ?

The basic idea is that the ground loop is "busted" with a 10 Ohm
resistor. (That may or may not actually cure a hum problem, depends on
the sensitivity of the amplifier circuits involved) It does, however,
provide a reasonable ground path for static charges and RF filter
leakage.

To "short" RF noise to ground a capacitor is placed across the 10 Ohm.
This will not take care of frequencies in the "hum" range.

Finally a heavy current bridge is connected in such a way that it
passes current both directions. This might seem to be short that is
placed across the 10 Ohm resistor, but the truth is that these diodes
are non-linear devices. Their incremental impedance in response to
small signals depends upon the DC current through the device. Look at
the slope of the Diode forward bias curve. That it flattens out near
zero current is the key. But if there is a ground fault, and heavy
current occurs, the diodes pass the current with minimal voltage drop
and allow the tripping of breakers and fuses.

The device is "legal" so long as it's just plugged in to an outlet
(like the HUMplug) but as for "safe", that is another question! My
personal feeling a 35 Amp bridge is too small and a 15 amp bridge is
dangerous. You want the bridge to be large enough to trip breakers
and blow fuses. I'd use a 100 amp bridge for circuits fused in the
30-50 amp range (as many are). Most diodes take a pretty healthy
pulsed current, and failing open is more rare than shorted, but still
you should always remember the rule: SEMICONDUCTOR DEVICES MAKE MUCH
BETTER FUSES THAN FUSES! You obviously don't need a heat sink of the
kind that might be needed to handle a continuous 100 amps but the
higher the current (and voltage...you don't want the diodes failing
from a high voltage spike either!) rating the better.
You may have problems finding a bridge module over 50 amps, but four
1000 volt 100 amp stud diodes are not big deal.

hrhofmann@att.net

2007-06-16, 9:25 pm

On Jun 12, 7:30 am, Tomi Holger Engdahl <t...@pippuri.niksula.hut.fi>
wrote:
> Anyone has experience on this HUMplug-e product ?
>
> Web pagehttp://www.21best.com/21_best/electronic/security/video/filters/for_s...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 tohttp://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 pagehttp://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 athttp://www.epanorama.net/

Could it simply be a ferrite-based toroidal choke placed in series in
the ground lead? It would safely maintain the safety continuity, but
the high impedance would reduce the ground currents.

H. R.(Bob) Hofmann

Richard Crowley

2007-06-17, 1:25 pm

<hrhofmann@att.net> wrote ...
> Could it simply be a ferrite-based toroidal choke placed in series in
> the ground lead? It would safely maintain the safety continuity, but
> the high impedance would reduce the ground currents.

The ferrite choke would be "high impedance" only at
high frequencies. It would do nothing for typical ground-
loop currents.

Mr.T

2007-06-18, 3:25 am

"Richard Crowley" <rcrowley@xp7rt.net> wrote in message
news:137ahmdmo9kci08@corp.supernews.com...
> <hrhofmann@att.net> wrote ...
>
> The ferrite choke would be "high impedance" only at
> high frequencies. It would do nothing for typical ground-
> loop currents.

Yes, I wonder how "high" an impedance he thinks a small toroid is going to
be at 50/60 Hz!

MrT.

Tomi Holger Engdahl

2007-06-19, 9:25 am

"Richard Crowley" <rcrowley@xp7rt.net> writes:

> <hrhofmann@att.net> wrote ...
>
> The ferrite choke would be "high impedance" only at high
> frequencies. It would do nothing for typical ground-
> loop currents.

With suitably selected big ferrite core and more than few turns
it is very well possible to get millenries even at 50 Hz.
For example 10 mH inductance at 50 Hz is around 3 ohms impedance.
This value will definately reduce ground loop currents on
normal situations, but would it be then too much to
make the grounding connection not good enough for
electrical safety.

So my question is would any impedance value that is well
effective for solving round loop problems too high to be
added to the safety ground connection (would not be safe
in rela life and/or woudl not meet safety regulations) ?

I have made ground loop solving products that have been
connected audio and/or video lines. I have made many
experiments on different constructions. For signal lines
I have tried different ferrite material, toroidal cores
(simular as used in toroidal mains transformers),
E-cores etc.. Different contructions have their all good
and bad properties. With suitable ferrite selection
is possible to get inductances that are high enough
for solving ground loop problems on signal lines.
The downside is that materials with what I can get
high inducances with reasonable number of turns
tend to saturate quite easily.

--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/

dpierce@cartchunk.org

2007-06-19, 9:25 am

On Jun 19, 6:44 am, Tomi Holger Engdahl <t...@pippuri.niksula.hut.fi>
wrote:
> "Richard Crowley" <rcrow...@xp7rt.net> writes:
>
>
> With suitably selected big ferrite core and more than few turns
> it is very well possible to get millenries even at 50 Hz.

Uh, ignoring core losses and other parasitics,
you'll get whatever inductance you get inductance
you get at ANY frequency. You don't get "millihenries
at 50 Hz", you get millihenries.

> For example 10 mH inductance at 50 Hz is around 3
> ohms impedance.

Yeah, and to get 10 mH, you'd need a LOT "more
than a few turns." And unless you wound it with sufficiently
large-gauge wire, you'd have a fair amount of resistance
as well.

Why you'd want any appreciable impedance in a safety
ground could be a puzzle to some.

phil-news-nospam@ipal.net

2007-06-19, 1:25 pm

In alt.engineering.electrical dpierce@cartchunk.org wrote:
| On Jun 19, 6:44 am, Tomi Holger Engdahl <t...@pippuri.niksula.hut.fi>
| wrote:
|> "Richard Crowley" <rcrow...@xp7rt.net> writes:
|> > <hrhofm...@att.net> wrote ...
|> > > Could it simply be a ferrite-based toroidal choke placed in series in
|> > > the ground lead? It would safely maintain the safety continuity, but
|> > > the high impedance would reduce the ground currents.
|>
|> > The ferrite choke would be "high impedance" only at high
|> > frequencies. It would do nothing for typical ground-
|> > loop currents.
|>
|> With suitably selected big ferrite core and more than few turns
|> it is very well possible to get millenries even at 50 Hz.
|
| Uh, ignoring core losses and other parasitics,
| you'll get whatever inductance you get inductance
| you get at ANY frequency. You don't get "millihenries
| at 50 Hz", you get millihenries.
|
|> For example 10 mH inductance at 50 Hz is around 3
|> ohms impedance.
|
| Yeah, and to get 10 mH, you'd need a LOT "more
| than a few turns." And unless you wound it with sufficiently
| large-gauge wire, you'd have a fair amount of resistance
| as well.
|
| Why you'd want any appreciable impedance in a safety
| ground could be a puzzle to some.

If they don't know about the ground loop problem. The metallic interconnect
between equipment is what makes this so hard. There is the loop being
formed.

Maybe more effort needs to be put into why it is that the ground gets so
much current induced into it.

--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / spamtrap-2007-06-19-1238@ipal.net |
|------------------------------------/-------------------------------------|

GregS

2007-06-19, 1:25 pm

In article <f594e703r3@news5.newsguy.com>, phil-news-nospam@ipal.net wrote:
>In alt.engineering.electrical dpierce@cartchunk.org wrote:
>| On Jun 19, 6:44 am, Tomi Holger Engdahl <t...@pippuri.niksula.hut.fi>
>| wrote:
>|> "Richard Crowley" <rcrow...@xp7rt.net> writes:
>|> > <hrhofm...@att.net> wrote ...
>|> > > Could it simply be a ferrite-based toroidal choke placed in series in
>|> > > the ground lead? It would safely maintain the safety continuity, but
>|> > > the high impedance would reduce the ground currents.
>|>
>|> > The ferrite choke would be "high impedance" only at high
>|> > frequencies. It would do nothing for typical ground-
>|> > loop currents.
>|>
>|> With suitably selected big ferrite core and more than few turns
>|> it is very well possible to get millenries even at 50 Hz.
>|
>| Uh, ignoring core losses and other parasitics,
>| you'll get whatever inductance you get inductance
>| you get at ANY frequency. You don't get "millihenries
>| at 50 Hz", you get millihenries.
>|
>|> For example 10 mH inductance at 50 Hz is around 3
>|> ohms impedance.
>|
>| Yeah, and to get 10 mH, you'd need a LOT "more
>| than a few turns." And unless you wound it with sufficiently
>| large-gauge wire, you'd have a fair amount of resistance
>| as well.
>|
>| Why you'd want any appreciable impedance in a safety
>| ground could be a puzzle to some.
>
>If they don't know about the ground loop problem. The metallic interconnect
>between equipment is what makes this so hard. There is the loop being
>formed.
>
>Maybe more effort needs to be put into why it is that the ground gets so
>much current induced into it.

There are many ways to induce current.

The one thing thats clear to me is, providing some RFI filtering to
the ground along with hot and neutral, is good.

Who is going to buy one of these hum gadgets and find out whats inside?

greg

Richard Crowley

2007-06-19, 1:25 pm

"GregS" wrote ...
> Who is going to buy one of these hum gadgets and find out whats inside?

If they're smart, they potted it. Likely the only way to prevent easy
reverse-engineering (and subsequent cloning in some cheap far-
east factory.)

Fred Abse

2007-06-19, 1:25 pm

On Tue, 19 Jun 2007 05:28:29 -0700, dpierce wrote:

> Uh, ignoring core losses and other parasitics,
> you'll get whatever inductance you get inductance
> you get at ANY frequency. You don't get "millihenries
> at 50 Hz", you get millihenries.

Only if the core is air, or vacuum.

The permeability of any ferromagnetic core varies with frequency, hence
the inductance of a coil wound on such a core will vary with frequency,
too.Some ferrites would be totally useless at 50 Hz. Laminated silicon
iron stampings would work at 50 Hz and be no good at, say 100KHz.

This is different from "core losses", which are resistive.

The *apparent* inductance will be affected by winding capacitance as well.
Above its self-resonant frequency, an "inductor" looks like a capacitor.

There's nothing wrong with Tomi's statement.

--
"Electricity is of two kinds, positive and negative. The difference
is, I presume, that one comes a little more expensive, but is more
durable; the other is a cheaper thing, but the moths get into it."
(Stephen Leacock)

LinkBot