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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => AC Power and Grounding => Topic started by: Mike Sokol on September 23, 2013, 01:31:36 pm

Title: Name that gadget
Post by: Mike Sokol on September 23, 2013, 01:31:36 pm
Take a look at this handy gadget. They only cost a buck or two, but can not only help improve your sound system, it can also help prevent an entire building's electrical system from burning up.

(http://howtosound.com/images/FerriteCore.jpg)

So what is it and what does it do? There's actually two correct answers (maybe three) but one of them is its most important function (IMHO).

I'll post the answer next Monday.
Title: Re: Name that gadget
Post by: John Roberts {JR} on September 23, 2013, 01:49:29 pm
I've never seen one that big.. But I don't work with that kind of stuff.


JR
Title: Re: Name that gadget
Post by: Corey Scogin on September 23, 2013, 01:52:20 pm
They help attenuate noise that may be carried through the cable to which they attach.  That noise may be from a device, the electrical system, or noise picked up from the environment where the cable is acting like an antenna.  I'm guessing they are most effective at attenuating higher frequencies...outside the power 50/60 hz range or the audible range of < 20 kHz ?
Title: Re: Name that gadget
Post by: Greg_Cameron on September 23, 2013, 01:55:30 pm
http://en.wikipedia.org/wiki/Ferrite_bead
Title: Re: Name that gadget
Post by: gary makovsky on September 23, 2013, 01:55:44 pm
Take a look at this handy gadget. They only cost a buck or two, but can not only help improve your sound system, it can also help prevent an entire building's electrical system from burning up.

(http://howtosound.com/images/FerriteCore.jpg)

So what is it and what does it do? There's actually two correct answers (maybe three) but one of them is its most important function (IMHO).

I'll post the answer next Monday.

AC line Ferrite filter for blocking noise on incoming power. Usually a last minute fix required to prevent EMI for FCC or UL compliance.  As far as preventing a building system from burning up ???? Not sure how RF energy put back on a AC line could do that.
Title: Re: Name that gadget
Post by: Mike Sokol on September 23, 2013, 04:21:24 pm
As far as preventing a building system from burning up ???? Not sure how RF energy put back on a AC line could do that.

I know this is true because it happened to me where I worked in the 70's. This was in a million square foot warehouse with a 100,000 square foot production floor. Took out the entire electrical system, and the plant was was down for days with hundreds of exploded bulbs, ballasts, and electrical controls. 

Hmmmm..... How could this happen???  ;D

The little gadget shown above might have made a difference.

I'll give you all a hint: Triplen Harmonics....  ::)
Title: Re: Name that gadget
Post by: Greg_Cameron on September 23, 2013, 07:08:31 pm
I know this is true because it happened to me where I worked in the 70's. This was in a million square foot warehouse with a 100,000 square foot production floor. Took out the entire electrical system, and the plant was was down for days with hundreds of exploded bulbs, ballasts, and electrical controls. 

Hmmmm..... How could this happen???  ;D

The little gadget shown above might have made a difference.

I'll give you all a hint: Triplen Harmonics....  ::)

Triplen harmonic frequencies are well below the RF range in 3 phase power systems, . I don't see any evidence that ferrite beads of a conventional nature are able to operate anywhere near there. And the most problematic harmonics are the lower frequency harmonics closest to the fundamental.
Title: Re: Name that gadget
Post by: Mike Sokol on September 24, 2013, 04:38:58 pm
Triplen harmonic frequencies are well below the RF range in 3 phase power systems, . I don't see any evidence that ferrite beads of a conventional nature are able to operate anywhere near there. And the most problematic harmonics are the lower frequency harmonics closest to the fundamental.


That's true, but I have one report of an office building full of desktop computers with switching power supplies that burned up the neutral bus via Triplen harmonics. It's not just 3rd order harmonics, but also 5th, 7th, 9th, 11th, 15th, 19th, 21st etc... I don't think there's a top end to it.

Some of these harmonics are created primarily by variable speed motor controllers, some by Thyristor light dimmers, and some by inverter power supplies in computers. I've just begun to think about modern power amplifiers with switching supplies. All of these odd-order harmonics can be additive on the neutral of a 3-phase power system rather than subtractive and can cause trouble with neutral overheating. 
Title: Re: Name that gadget
Post by: TJ (Tom) Cornish on September 24, 2013, 05:16:47 pm


That's true, but I have one report of an office building full of desktop computers with switching power supplies that burned up the neutral bus via Triplen harmonics. It's not just 3rd order harmonics, but also 5th, 7th, 9th, 11th, 15th, 19th, 21st etc... I don't think there's a top end to it.

Some of these harmonics are created primarily by variable speed motor controllers, some by Thyristor light dimmers, and some by inverter power supplies in computers. I've just begun to think about modern power amplifiers with switching supplies. All of these odd-order harmonics can be additive on the neutral of a 3-phase power system rather than subtractive and can cause trouble with neutral overheating.
According to this: http://www.csgnetwork.com/harmonicscalc.html the 15th harmonic of 60Hz is only 960Hz.  I find it hard to believe there's substantial power at harmonics much past the first few cycles.

I spent some time chasing down the 1500KHz radio station in some signal wiring of my house.  It took several turns on a ferrite with the lowest operating frequency I could find to knock it out.  Pretty sure the attenuation of my ferrite beads would be very close to 0 at 1KHz or less.

PFC power supplies make a difference as they make the load appear to be closer to linear, reducing the potential for triplen issues.  All of the servers at my company have PFC supplies, and most of our desktops do too.  I don't think there's been much progress on dimmers - sinewave dimmers are still rare and expensive.
Title: Re: Name that gadget
Post by: Greg_Cameron on September 24, 2013, 05:52:01 pm
Also, the triplen harmonics generated by switch mode supplies have rapid energy drop off as you go up in harmonic order/frequency. The following is a typical graph:

(http://www.marcspages.co.uk/pq/5150a.gif).

So even if you could get a ferrite bead that would get down into the upper end of the audible band, it's not going to do much good unless it can work down to a pretty low frequency.
Title: Re: Name that gadget
Post by: Mike Sokol on September 24, 2013, 07:44:34 pm
Also, the triplen harmonics generated by switch mode supplies have rapid energy drop off as you go up in harmonic order/frequency. The following is a typical graph:

So even if you could get a ferrite bead that would get down into the upper end of the audible band, it's not going to do much good unless it can work down to a pretty low frequency.

You might be right about the ferrite cores not attenuating the lower harmonics enough to be beneficial to reduce Triplen currents from motor speed controllers.  I do know that we added series inductors to reduce the harmonics of thyristor light dimmers and motor controllers, and that stopped the neutral overheating. Also, before a lot of non-linear loads were introduced, it was common practice to undersize the neutral wire in a 3-phase WYE circuit because the different phase currents were normally subtractive. So a 100-amp, 3-phase circuit might only have a 60-amp sized neutral simply because 3-phase motor loads would have no neutral currents at all. Fast forward to modern times and this same warehouse can now have dimmer lighting and all sorts of non-linear loads. That undersized neutral could be carrying way more than its 60 amp current rating, and that's when the real overheating problems start. 
Title: Re: Name that gadget
Post by: Jonathan Johnson on September 25, 2013, 05:42:19 pm
Also, before a lot of non-linear loads were introduced, it was common practice to undersize the neutral wire in a 3-phase WYE circuit because the different phase currents were normally subtractive. So a 100-amp, 3-phase circuit might only have a 60-amp sized neutral simply because 3-phase motor loads would have no neutral currents at all. Fast forward to modern times and this same warehouse can now have dimmer lighting and all sorts of non-linear loads. That undersized neutral could be carrying way more than its 60 amp current rating, and that's when the real overheating problems start.

Sounds like we need a new type of circuit breaker that also measures current in the neutral, and when that current exceeds a safe value, disconnects the hot/live lines related to that neutral.
Title: Re: Name that gadget
Post by: Mike Sokol on September 26, 2013, 08:32:50 am
Sounds like we need a new type of circuit breaker that also measures current in the neutral, and when that current exceeds a safe value, disconnects the hot/live lines related to that neutral.

I worked in an 1890's theater once, and ALL the neutrals had fuses. Guess that's how it was done back in the day. Of course, we now know that's a bad idea. If you're ever working around K&T (Knob & Tube) wiring, watch out for neutral fuses.
Title: Re: Name that gadget
Post by: Jonathan Johnson on September 26, 2013, 01:45:15 pm
I worked in an 1890's theater once, and ALL the neutrals had fuses. Guess that's how it was done back in the day. Of course, we now know that's a bad idea. If you're ever working around K&T (Knob & Tube) wiring, watch out for neutral fuses.

That's why I didn't suggest interrupting the neutral -- bad idea (unless you can guarantee than any and all feeds that use that neutral are also interrupted). I probably could have made it more clear.
Title: Re: Name that gadget
Post by: Jonathan Johnson on February 20, 2015, 05:41:07 pm
So what is it and what does it do? There's actually two correct answers (maybe three) but one of them is its most important function (IMHO).

Not to be confused with a Ferret Bead:

(http://www.artfire.com/uploads/product/1/821/85821/8085821/8085821/large/pandora_biagi_trollbeads_handmade_lampwork_charm_bead_funny_ferret_sra_5164f5bf.jpg)
Title: Re: Name that gadget
Post by: Stephen Swaffer on February 20, 2015, 06:46:37 pm
Sounds like we need a new type of circuit breaker that also measures current in the neutral, and when that current exceeds a safe value, disconnects the hot/live lines related to that neutral.

The NEC/NFPA has taken the approach of putting the responsibility on the electrician/engineer involved.  I had a friend that failed to follow through on getting his license when the state began requiring them-he wanted to cherry pick and take the high profit lighting upgrades at a mutual customer saying it was just replacement.  The state (Iowa) allows non-electricians to do repairs-but not installs.  I posed the question to the state inspector and his response was that since the load was changing an electrician had to be involved.

Many people think wiring is simple "anyone can do it"-but things like this are brought up in required continuing ed classes for electricians for a reason.  And an electricians rate reflects the time and money invested in classes, of course, there is no guarantee that the electrician you hire will be conscientious enough to do it right-and if the job is bid without engineering specs and really needs a neutral upgrade, then the electrician that includes that will likely not be the low bid.   
Title: Re: Name that gadget
Post by: Frank Koenig on February 21, 2015, 12:16:29 pm
Triplen harmonic frequencies are well below the RF range in 3 phase power systems, . I don't see any evidence that ferrite beads of a conventional nature are able to operate anywhere near there. And the most problematic harmonics are the lower frequency harmonics closest to the fundamental.

I agree. A quick look at the Digi-Key catalog shows their ferrite beads' impedance rated at 25 and 100 MHz, well above power line harmonic frequencies.

As a circuit element a ferrite bead on a wire behaves more-or-less as a frequency dependent resistor with the resistance increasing with frequency. The resistance at operating frequency is in the range of a few hundred Ohms. The beauty is that as the series element in an EMI filter their lossy (low Q) nature avoids sharp resonances over a large range of external variables making for a robust filter. Unlike an ideal inductor, power is dissipated in the ferrite. Pump enough RF into one and you should be able to blow it up, or at least cook it, although I've never seen this done.

If your filter design needs higher series impedance or has to operate at lower (power line) frequency, use a coil, along with all its fiddly trade-offs.

--Frank 
Title: Re: Name that gadget
Post by: Mike Sokol on February 21, 2015, 05:20:52 pm
If your filter design needs higher series impedance or has to operate at lower (power line) frequency, use a coil, along with all its fiddly trade-offs.

I've used these Neutrik EMC connectors with an integral ferrite bead and RF capacitors to knock out AM radio stations. See the full specs at http://www.neutrik.com/en/xlr/emc-series/nc3mxx-emc (http://www.neutrik.com/en/xlr/emc-series/nc3mxx-emc)
Title: Re: Name that gadget
Post by: Tim McCulloch on February 21, 2015, 07:12:30 pm
I've used these Neutrik EMC connectors with an integral ferrite bead and RF capacitors to knock out AM radio stations. See the full specs at http://www.neutrik.com/en/xlr/emc-series/nc3mxx-emc (http://www.neutrik.com/en/xlr/emc-series/nc3mxx-emc)

Yes.  The Mackie VLZ radio station removal XLR.

We serviced a house of worship that replaced their old Peavey 700 series with a new Mackie.  You had your choice of sports talk, country/western or oldies rock depending on which of the affected channels you raised.  New wire had been pulled, the workmanship was good, but the Mackie was happy to demodulate the AM.  Ferrite beads were applied and chicken bones were cast.  The AM was rebuked.
Title: Re: Name that gadget
Post by: Mike Sokol on February 21, 2015, 07:49:38 pm
Yes.  The Mackie VLZ radio station removal XLR.

Yup, sort of like your own crystal radio set. Remember those?
Title: Re: Name that gadget
Post by: Guy Holt on February 21, 2015, 08:06:51 pm
Sounds like we need a new type of circuit breaker that also measures current in the neutral, and when that current exceeds a safe value, disconnects the hot/live lines related to that neutral.

Such a breaker, the electronic ABB TMAX, is pretty much standard in film disconnects. With the PR221DS-LS/I controller, it can be set to trip when current on the neutral reaches 50 or 100% of the over current protection setting for the phase legs. Over current protection  for the phase legs is variable between 160 and 400 Amps.

Guy Holt, Gaffer
ScreenLight & Grip
www.screenlightandgrip.com
Title: Re: Name that gadget
Post by: Guy Holt on February 21, 2015, 08:44:27 pm
... I have one report of an office building full of desktop computers with switching power supplies that burned up the neutral bus via Triplen harmonics. It's not just 3rd order harmonics, but also 5th, 7th, 9th, 11th, 15th, 19th, 21st etc... I don't think there's a top end to it. ...

It is not just the neutral conductor that we have to be concerned about. The predominant transformer used in commercial/residential applications, a Delta/Wye has some undesirable characteristics when significant amounts of harmonic currents are present on the load side. For instance, since a Delta primary does not have a neutral, the induced currents do not flow through the primary system, and if they are not cancelled, they become trapped in the primary where they continuously circulate causing extra heating. Called “Eddy Currents”, these currents produce heat that increases substantially at the higher harmonic frequencies. The relationship is as follows:

(http://www.screenlightandgrip.com/images/generators/Pro_Sound_Paralleling_Copy_Overheating.jpg)
(Where: PEC = Total eddy current losses, PEC-1 = Eddy current losses at full load based on linear loading only.

Ih = rms current (per unit) at harmonic h , and h = harmonic # )

What is significant about the relationship of Eddy Current heat loss as a result of harmonic currents expressed in this equation is that the harmonic current (Ih) and harmonic number (h) are squared which means that instead of increasing in a linear fashion they increase exponentially. Put another way, the heat generated by harmonic currents just doesn’t increase gradually at higher harmonic frequencies, but it jumps drastically.

As indicated in the equation above, higher order harmonics will generate as much heat as the 3rd, but at much lower amplitudes. For instance, according to the equation above 1 Amp of the 5th harmonic will generate as much heat as 1.7 Amps of the 3rd, and 1 Amp of the 9th harmonic will generate as much heat as 9 Amps of the 3rd. For this reason, the higher order triplen harmonics contribute as much to distribution equipment  overheating as the lower frequency. For instance, it doesn’t take much 21st harmonic current to generate heat when, according to the equation above, the harmonic frequency (h) is squared for a multiplier of 441x (212) compared to the multiplier of 9x (32) for the 3rd harmonic.

Guy Holt, Gaffer
ScreenLight & Grip
www.screenlightandgrip.com
Title: Re: Name that gadget
Post by: Keith Broughton on February 22, 2015, 06:02:25 am


As indicated in the equation above, higher order harmonics will generate as much heat as the 3rd, but at much lower amplitudes. For instance, according to the equation above 1 Amp of the 5th harmonic will generate as much heat as 1.7 Amps of the 3rd, and 1 Amp of the 9th harmonic will generate as much heat as 9 Amps of the 3rd. For this reason, the higher order triplen harmonics contribute as much to distribution equipment  overheating as the lower frequency. For instance, it doesn’t take much 21st harmonic current to generate heat when, according to the equation above, the harmonic frequency (h) is squared for a multiplier of 441x (212) compared to the multiplier of 9x (32) for the 3rd harmonic.

Guy Holt, Gaffer
ScreenLight & Grip
www.screenlightandgrip.com
That is a very interesting effect. Well explained.
Learn something every day here :)
Title: Re: Name that gadget
Post by: Kevin Graf on February 22, 2015, 11:58:01 am
For more on 3 phase AC power and harmonics see pages 6 & 7 of this Jim Brown paper:

"Power and Grounding For Audio and Audio/Video Systems -- A White Paper for the Real World"
http://www.audiosystemsgroup.com/SurgeXPowerGround.pdf

50 more Jim Brown papers:
http://www.audiosystemsgroup.com/publish.htm
Title: Re: Name that gadget
Post by: Keith Broughton on February 22, 2015, 02:11:16 pm
For more on 3 phase AC power and harmonics see pages 6 & 7 of this Jim Brown paper:

"Power and Grounding For Audio and Audio/Video Systems -- A White Paper for the Real World"
http://www.audiosystemsgroup.com/SurgeXPowerGround.pdf

50 more Jim Brown papers:
http://www.audiosystemsgroup.com/publish.htm
I just read through some of the EMI/RFI problems and trouble shooting.
Compared to that, ground loops are easy!
Thanks for the links.