Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[tomfabjance]

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?

[Tim McCulloch]

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?

[John Moore]

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.

[Charlie Zureki]

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

[paul bell]

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.

[Ricky Lighthall]

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.

[Geoff Doane]

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

[Peter Morris]

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

[Tim McCulloch]

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

[Jonathan Johnson]

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?

[ProSoundWeb Community]