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Author Topic: 3 Phase 200 Amp Isolated Audio Transformer  (Read 16030 times)

tomfabjance

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3 Phase 200 Amp Isolated Audio Transformer
« on: July 02, 2011, 09:19:48 pm »

Hello.  I'm wondering if anybody has any experience with using 3 Phase Iso-Transformers?  And whether or not they actually work?

We have this 12.5k hertz electrical noise that comes intermittently through our speakers, caused by the new electronic meter reading system that the local electric company installed.  Every time the meter is read at any home or business between us and the AC node down at the bottom of the hill, we get a series of 12.5k hertz "rings" through FOH & monitors.

Thus far the solution has been to call the power company on show days and have them switch off the automated readings.

I'm thinking that an iso transformer may solve this once and for all?
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Tim McCulloch

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Re: 3 Phase 200 Amp Isolated Audio Transformer
« Reply #1 on: July 02, 2011, 10:26:50 pm »

Hello.  I'm wondering if anybody has any experience with using 3 Phase Iso-Transformers?  And whether or not they actually work?

We have this 12.5k hertz electrical noise that comes intermittently through our speakers, caused by the new electronic meter reading system that the local electric company installed.  Every time the meter is read at any home or business between us and the AC node down at the bottom of the hill, we get a series of 12.5k hertz "rings" through FOH & monitors.

Thus far the solution has been to call the power company on show days and have them switch off the automated readings.

I'm thinking that an iso transformer may solve this once and for all?

What does your utility company say?
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John Moore

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Re: 3 Phase 200 Amp Isolated Audio Transformer
« Reply #2 on: July 03, 2011, 12:36:56 am »

Hello.  I'm wondering if anybody has any experience with using 3 Phase Iso-Transformers?  And whether or not they actually work?

We have this 12.5k hertz electrical noise that comes intermittently through our speakers, caused by the new electronic meter reading system that the local electric company installed.  Every time the meter is read at any home or business between us and the AC node down at the bottom of the hill, we get a series of 12.5k hertz "rings" through FOH & monitors.

Thus far the solution has been to call the power company on show days and have them switch off the automated readings.

I'm thinking that an iso transformer may solve this once and for all?

Are you sure it is the utility co.? Do you have a school or hospital close by that could be using a carrier current correcting clock system that is leaking back into the grid? They send out corrections every hour, some every minute.
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Charlie Zureki

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Re: 3 Phase 200 Amp Isolated Audio Transformer
« Reply #3 on: July 03, 2011, 12:39:08 am »

Hello.  I'm wondering if anybody has any experience with using 3 Phase Iso-Transformers?  And whether or not they actually work?

We have this 12.5k hertz electrical noise that comes intermittently through our speakers, caused by the new electronic meter reading system that the local electric company installed.  Every time the meter is read at any home or business between us and the AC node down at the bottom of the hill, we get a series of 12.5k hertz "rings" through FOH & monitors.

Thus far the solution has been to call the power company on show days and have them switch off the automated readings.

I'm thinking that an iso transformer may solve this once and for all?


  Hello,

  I don't think it will filter this 12.5k ping.

  But, they should have a solution.  If you take into account the current legislation regarding injecting noise on the AC grid...they should comply also.

   Hammer
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paul bell

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Re: 3 Phase 200 Amp Isolated Audio Transformer
« Reply #4 on: July 03, 2011, 09:50:47 am »

I agree with Charlie about the noise they're injecting into the line.

I've seen many events where they sound system has a huge isolation transformer. Unfortunately, a transformer will duplicate at it's output what it sees on the input. They often cause more problems than they solve. Some sound companies always use transformers before they even try to use the power without it first.

While my systems are not 100,000+ watts line array hangs, I can reach about 50Kw. I've always tied directly into commercial power often paralleled with the lighting feed without ever having an issue.

The bottom line, in my opinion, is that using a power isolation transformer will not filter out the noise.
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Ricky Lighthall

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Re: 3 Phase 200 Amp Isolated Audio Transformer
« Reply #5 on: July 03, 2011, 01:06:38 pm »

Hello.  I'm wondering if anybody has any experience with using 3 Phase Iso-Transformers?  And whether or not they actually work?

We have this 12.5k hertz electrical noise that comes intermittently through our speakers, caused by the new electronic meter reading system that the local electric company installed.  Every time the meter is read at any home or business between us and the AC node down at the bottom of the hill, we get a series of 12.5k hertz "rings" through FOH & monitors.

Thus far the solution has been to call the power company on show days and have them switch off the automated readings.

I'm thinking that an iso transformer may solve this once and for all?

If the noise is being injected on the neutral an iso might help.  Three phase iso's do not use the neutral on the primary side and create it on the secondary so any noise on the neutral, like dimmer rack hash, doesn't pass through.
It is also possible to build low pass filters like they use at substations, but it's serious coin.
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Geoff Doane

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Re: 3 Phase 200 Amp Isolated Audio Transformer
« Reply #6 on: July 03, 2011, 09:45:19 pm »

My experience with trying to get rid of noise on the line with isolation transformers hasn't been all that encouraging.  We had a problem with certain components in a system, that was caused by a building UPS, which none of the usual tricks could solve.

The solution we came up with was to power the equipment from a dual conversion UPS of its own.  A dual conversion (sometimes called on-line) UPS takes the line voltage, rectifies it to DC and charges batteries.  The DC from there then goes to an inverter which synthesizes a brand new AC waveform, this time free of the noise.

In our case it was only certain devices (one brand of powered speakers) that was picking up the noise.  All the other equipment in the PA and studio seemed immune.  It might be worthwhile trying to determine if that is your case as well, and perhaps you can fix the problem with 2 KVA of UPS rather than 75 KVA!  If the problem is intermittent, that may be easier said than done. :(

GTD
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Peter Morris

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Re: 3 Phase 200 Amp Isolated Audio Transformer
« Reply #7 on: July 03, 2011, 10:17:20 pm »

My experience with trying to get rid of noise on the line with isolation transformers hasn't been all that encouraging.  We had a problem with certain components in a system, that was caused by a building UPS, which none of the usual tricks could solve.

The solution we came up with was to power the equipment from a dual conversion UPS of its own.  A dual conversion (sometimes called on-line) UPS takes the line voltage, rectifies it to DC and charges batteries.  The DC from there then goes to an inverter which synthesizes a brand new AC waveform, this time free of the noise.

In our case it was only certain devices (one brand of powered speakers) that was picking up the noise.  All the other equipment in the PA and studio seemed immune.  It might be worthwhile trying to determine if that is your case as well, and perhaps you can fix the problem with 2 KVA of UPS rather than 75 KVA!  If the problem is intermittent, that may be easier said than done. :(

GTD


I haven’t tried this  -  but a ferro resonant transformer may help – I have seen them on ebay quite cheap from time to time.  They are probably listed under voltage regulator transformers …

http://www.ustpower.com/Support/Voltage_Regulator_Comparison/Ferroresonant_Transformer_CVT.aspx

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Tim McCulloch

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Re: 3 Phase 200 Amp Isolated Audio Transformer
« Reply #8 on: July 03, 2011, 11:26:23 pm »

My experience with trying to get rid of noise on the line with isolation transformers hasn't been all that encouraging.  We had a problem with certain components in a system, that was caused by a building UPS, which none of the usual tricks could solve.

The solution we came up with was to power the equipment from a dual conversion UPS of its own.  A dual conversion (sometimes called on-line) UPS takes the line voltage, rectifies it to DC and charges batteries.  The DC from there then goes to an inverter which synthesizes a brand new AC waveform, this time free of the noise.

In our case it was only certain devices (one brand of powered speakers) that was picking up the noise.  All the other equipment in the PA and studio seemed immune.  It might be worthwhile trying to determine if that is your case as well, and perhaps you can fix the problem with 2 KVA of UPS rather than 75 KVA!  If the problem is intermittent, that may be easier said than done. :(

GTD


I haven’t tried this  -  but a ferro resonant transformer may help – I have seen them on ebay quite cheap from time to time.  They are probably listed under voltage regulator transformers …

http://www.ustpower.com/Support/Voltage_Regulator_Comparison/Ferroresonant_Transformer_CVT.aspx

Hi Peter-

Your post got me to thinking about the electrical service installed at a State Park pavilion... the service labeled "Entertainment" is on a 35 KVA ferro-resonant transformer.  All the other power is right off the step-down 480/240v transformer.  Next time I'm out there, I'll take another look and talk to the park electrician for more details, but I recall it was installed because the service was "noisy".

Thanks for the memory jog.

Tim Mc
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Jonathan Johnson

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Re: 3 Phase 200 Amp Isolated Audio Transformer
« Reply #9 on: July 03, 2011, 11:37:13 pm »

We have this 12.5k hertz electrical noise that comes intermittently through our speakers...

I'm thinking that an iso transformer may solve this once and for all?
As a general rule, a simple transformer will block a DC voltage bias, but being designed to transform the voltage of AC signals, it cannot block an AC signal, such as the 12.5kHz carrier signal from the electrical meters. Of course, transformer construction, additional electronics in the transformer, or the way the signal is transmitted (i.e., on the neutral) may affect your results.

Have you considered the option of having the utility install a transformer dedicated to your facility, and using a different means of reading the meter -- perhaps a meter installed on the primary side of your transformer?
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Peter Morris

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Re: 3 Phase 200 Amp Isolated Audio Transformer
« Reply #10 on: July 04, 2011, 02:15:59 am »


I haven’t tried this  -  but a ferro resonant transformer may help – I have seen them on ebay quite cheap from time to time.  They are probably listed under voltage regulator transformers …

http://www.ustpower.com/Support/Voltage_Regulator_Comparison/Ferroresonant_Transformer_CVT.aspx


Hi Peter-

Your post got me to thinking about the electrical service installed at a State Park pavilion... the service labeled "Entertainment" is on a 35 KVA ferro-resonant transformer.  All the other power is right off the step-down 480/240v transformer.  Next time I'm out there, I'll take another look and talk to the park electrician for more details, but I recall it was installed because the service was "noisy".

Thanks for the memory jog.

Tim Mc

Soo … it’s not just me that had that thought …. thanks

As you would know, one of the things that a ferro-resonant transformer does in addition to maintain a constant voltage is act as a low-pass filter, effectively removing transient and surge voltages.

The energy stored in the transformer and associated circuit allows the output to "ride through" brief input power interruptions.
« Last Edit: July 04, 2011, 09:14:29 am by Peter Morris »
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Jeff Robinson

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Re: 3 Phase 200 Amp Isolated Audio Transformer
« Reply #11 on: July 05, 2011, 12:23:08 am »

Soo … it’s not just me that had that thought …. thanks

As you would know, one of the things that a ferro-resonant transformer does in addition to maintain a constant voltage is act as a low-pass filter, effectively removing transient and surge voltages.

The energy stored in the transformer and associated circuit allows the output to "ride through" brief input power interruptions.

Ferro-resonant transformers add distortion to the ac waveform. They also really do not like to exceed their rated kva, ever. You do not want your gear hooked up if the capacitor in the tank circuit ever fails.

12.5kHz may be a beat frequency of the real carrier frequency. If it is above a few mHz a shielded power transformer could help (they generally have 20+dB noise reduction), also called a Faraday shield. This is a standard feature of Acme brand and an option in other brands.

There are power line filters in several brands also, available in a range of amperage ratings. MTE likely has some listed on their website.

HTH

Jeff Robinson
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Jim McKeveny

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Re: 3 Phase 200 Amp Isolated Audio Transformer
« Reply #12 on: July 05, 2011, 10:09:26 am »

I must echo some of the previous posters comments: I have seen "engineers" demand iso transformers when the issues were much simpler/cheaper to remedy. There may indeed be some global junk in the power, but for it to be substantial enough to upset lots of gear downstream....rare.
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Greg Longtin

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Re: 3 Phase 200 Amp Isolated Audio Transformer
« Reply #13 on: July 05, 2011, 01:42:40 pm »

Tom,

a series of 12.5k hertz "rings" through FOH & monitors

That transformer will be rather expensive.  Have you tried all other possible solutions?  You mentioned 'FOH & monitors', in what other equipment earlier in the signal chain do the 'rings' exist?

IOW, rather than add filtering/conditioning for the *whole* rig, just fix the offending pieces.

Some possible solutions are line level iso transformers, grounding and/or shielding changes, SurgeX, JuiceGoose, AC filtering, etc.  At one point Corcom made a very good 20 amp three phase line filter.  We used it for all line level monitor gear.

Greg
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Charlie Zureki

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Re: 3 Phase 200 Amp Isolated Audio Transformer
« Reply #14 on: July 05, 2011, 02:52:45 pm »

Tom,

That transformer will be rather expensive.  Have you tried all other possible solutions?  You mentioned 'FOH & monitors', in what other equipment earlier in the signal chain do the 'rings' exist?

IOW, rather than add filtering/conditioning for the *whole* rig, just fix the offending pieces.

Some possible solutions are line level iso transformers, grounding and/or shielding changes, SurgeX, JuiceGoose, AC filtering, etc.  At one point Corcom made a very good 20 amp three phase line filter.  We used it for all line level monitor gear.

Greg

   Hello,

   If there is a 12.5k hertz signal superimposed on the line power, line level transformers, surgeX, and juicegoose devices will not filter it out.

  More than likely, the 12.5k signal is getting into the system through the Amplifiers and not as much through the console or processing gear. 

  Hammer
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Charlie Zureki

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Re: 3 Phase 200 Amp Isolated Audio Transformer
« Reply #15 on: July 05, 2011, 03:02:30 pm »

Soo … it’s not just me that had that thought …. thanks

As you would know, one of the things that a ferro-resonant transformer does in addition to maintain a constant voltage is act as a low-pass filter, effectively removing transient and surge voltages.

The energy stored in the transformer and associated circuit allows the output to "ride through" brief input power interruptions.

Ferro-resonant transformers add distortion to the ac waveform. They also really do not like to exceed their rated kva, ever. You do not want your gear hooked up if the capacitor in the tank circuit ever fails.

12.5kHz may be a beat frequency of the real carrier frequency. If it is above a few mHz a shielded power transformer could help (they generally have 20+dB noise reduction), also called a Faraday shield. This is a standard feature of Acme brand and an option in other brands.

There are power line filters in several brands also, available in a range of amperage ratings. MTE likely has some listed on their website.

HTH

Jeff Robinson


  Hello,

   It is not a "beat frequency" , and a shielded transformer has nothing to do with the 12.5k signal that the Power Company injected into the power grid.

  Hammer
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Greg Longtin

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Re: 3 Phase 200 Amp Isolated Audio Transformer
« Reply #16 on: July 05, 2011, 06:50:12 pm »

Charlie,

If there is a 12.5k hertz signal superimposed on the line power, line level transformers, surgeX, and juicegoose devices will not filter it out.

  More than likely, the 12.5k signal is getting into the system through the Amplifiers and not as much through the console or processing gear.

1. SurgeX & JuiceGoose make many units that are both suppressors *and* filters.  Can't run racks of amps with them, but it may not be the amps.

2. I've come across equipment with poor hi-freq common rejection, so line level transformers *may* help, depending on where the noise is entering the system.

3. High frequency line noise is caused by all sorts of equipment, this isn't a unique problem.

Greg
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Charlie Zureki

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Re: 3 Phase 200 Amp Isolated Audio Transformer
« Reply #17 on: July 05, 2011, 09:19:45 pm »

Charlie,

If there is a 12.5k hertz signal superimposed on the line power, line level transformers, surgeX, and juicegoose devices will not filter it out.

  More than likely, the 12.5k signal is getting into the system through the Amplifiers and not as much through the console or processing gear.

1. SurgeX & JuiceGoose make many units that are both suppressors *and* filters.  Can't run racks of amps with them, but it may not be the amps.

2. I've come across equipment with poor hi-freq common rejection, so line level transformers *may* help, depending on where the noise is entering the system.

3. High frequency line noise is caused by all sorts of equipment, this isn't a unique problem.

Greg

   Hello,
      Surgex, Juice goose and etc...  work fairly well for current surge supression  and voltage spike protection. And, some of their advanced models will even out the current draws and help with voltage regulation ... keeping the output voltage within some spec established by the manufacturer...

   The filtering capabilities are only in regards to the unit's operation.

   These devices will not filter out a 12.5k sine wave that was added by the power utility.  Transformers pass Ac sinewaves they do not filter them out.

   While noise on power lines are a common problem... all electronic and electrical equipment that uses AC power sold in the U.S. is subject to standards written by the F.C.C.,..... in regards to outputting "noise" on the Electrical grid,  IEC, IEEE as well as F.C.C. for EFI and EMI  regulation.

  Hammer
     
« Last Edit: July 05, 2011, 10:05:38 pm by Charlie Zureki »
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Peter Morris

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Re: 3 Phase 200 Amp Isolated Audio Transformer
« Reply #18 on: July 05, 2011, 09:40:41 pm »

Ferro-resonant transformers add distortion to the ac waveform. They also really do not like to exceed their rated kva, ever. You do not want your gear hooked up if the capacitor in the tank circuit ever fails.

12.5kHz may be a beat frequency of the real carrier frequency. If it is above a few mHz a shielded power transformer could help (they generally have 20+dB noise reduction), also called a Faraday shield. This is a standard feature of Acme brand and an option in other brands.

There are power line filters in several brands also, available in a range of amperage ratings. MTE likely has some listed on their website.

HTH

Jeff Robinson

In a past life, I often used the approach you mentioned in industrial situations to protect PLC’s from noise - 1:1 transformer, Faraday shield and LC filtering. From memory, this approach tended not to be that effective at lower frequencies like 12K5, that’s assuming it’s a fundamental, which as you noted, it may not be.

FWIW as I understand, the frequency of powerline communication systems can be as low 12K, usually higher... but not in the MHz region.

I must confess I have only played with Ferro’s briefly as implied in my first post. I was aware of the wave form issues but I believe modern designs are probably OK – 5% distortion for those optimized for sin wave outputs. I do not know how well they would work in this application but as I understand, they would be more effective at the lower frequencies than the approach described above.   Manufactures claim one of their applications is as a “line conditioners to protect computers and other sensitive electronic devices from transients, noise, and surges on the power line.”

http://www.generaltransformer.com/transformer/ferroresonant-transformers.htm
http://www.foster-transformer.com/Transformers/FerroresonantTransformers.aspx 
http://www.icrepq.com/icrepq07/317-valverde.pdf
http://powerqualityworld.blogspot.com/2011/04/constant-voltage-ferroresonant.html


Peter
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tomfabjance

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Re: 3 Phase 200 Amp Isolated Audio Transformer
« Reply #19 on: July 28, 2011, 05:54:40 pm »

What does your utility company say?

The electric company has acknowledged the problem and has taken suit with the manufacturer of the new technology.  Nobody has found a solution thus far other than shutting it off when I call every week.  They claim to have engineers investigating, looking for a fix
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Re: 3 Phase 200 Amp Isolated Audio Transformer
« Reply #19 on: July 28, 2011, 05:54:40 pm »


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