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Audio equipment powered by different phases

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Audio equipment powered by different phases

Postby nazardo » Wed Sep 26, 2018 3:44 pm

I do not know if this is the right board to post this question, but I think there are a lot of people here with the knowledge to answer :wink:

I am designing a system which requires roughly 7 KW of power, with the possibility to reach 10 KW if further audio components are added. My church's electrician has suggested to me that it is best to split the power usage across the three phases (230V each, EU standard). Having a 10KW load on a single phase would require bigger cables, generate higher currents and require more expensive control circuits.

Are there any issues in splitting audio equipment across multiple AC lines? All will of course share the same neutral, as it is normal with three-phase power distribution.

Here is a distribution hypothesis I made as a reference:

Image

What do you think?

Thanks in advance
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Re: Audio equipment powered by different phases

Postby IainStinson » Wed Sep 26, 2018 7:44 pm

NB: This is not formal advice - you must get that from a certified electrician in your own region!

In the UK it would not be necessary to use a three phase installation - we would to use ring main circuits for this type of installation. https://en.wikipedia.org/wiki/Ring_circuit A ring main circuit enables up to 13 amps (3KW) to be drawn from one socket and up to 30 amps across the whole circuit using cable with a 10 amp capacity between each of the outlets and returning to consumer unit.

Three phase installations risk the possibility of 415 volt electrical shock (between the phases).

You need to comply with the regional safety regulations for all electrical installations and particularly for three phase installations you need to ensure it is correctly labeled and warning notices placed so anyone near or working on the installation is made fully aware of the risk of 415 volt shock across the phases. Where parts of an installation are on different phases, and in a generally accessible area, they should be separated by at least 2m (to reduce the risk of a person being able to reach across between units powered on different phases and potentially receive a 415 volt shock).

Our organ blower at church is a three phase motor, but the installation is completely contained in the blower unit and turned on using a star/delta starter with a single cable to the starting switch at the console. The console lights come the single phase ring main via a plug and socket.. (The pneumatic does not need any electricity!)

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Re: Audio equipment powered by different phases

Postby nazardo » Thu Sep 27, 2018 3:08 am

Thank you Iain, the reason why the electrician is suggesting to use all three phases and not only one is also to balance the power among the different phases in the building.

By the way, leaving aside all electrical concerns which I am sure will be properly handled, I am more interested if there will be issues for the audio chain if the computer, the amplifiers and the powered speakers are powered by different phases. Will the reproduced audio suffer in any way from this?
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Re: Audio equipment powered by different phases

Postby adrianw » Thu Sep 27, 2018 5:13 am

By the way, leaving aside all electrical concerns which I am sure will be properly handled, I am more interested if there will be issues for the audio chain if the computer, the amplifiers and the powered speakers are powered by different phases. Will the reproduced audio suffer in any way from this?


No, I understand why you might be concerned but I would not expect that to cause any audio problem.

However calculating the power demands of audio amplifiers for electrical supply purposes is not as straightforward as it may seem and your estimate of the total power demand (on which your electrician is presumably making his suggestions for phase distribution) might be unrealistic. If it were watt-for-watt, stadium concerts with their hundreds of kW of audio amplification would simply not be possible. You will be spending quite a bit of money and should get specialist advice.
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Re: Audio equipment powered by different phases

Postby organsRgreat » Thu Sep 27, 2018 6:00 am

There seems to be some confusion here between the phases of audio signals, and those of the mains power supply; but I cannot see that the two would be related. For mains power to be used by an amplifier it needs first to be rectified, and DC power, being continuous, cannot have a phase.

As adrianw has explained, the correspondence between mains power and speaker output power is not as simple as a one-to-one conversion. Before spending money on on high-powered amplification you might like to experiment with speakers of various power outputs. The amount of power required might be less than you expect. As a general rule a system with a large number of medium-powered speakers will produce a more realistic organ sound than a system with fewer speakers of higher power.

A pipe organ is not as “loud” an instrument as many people think. I once played for a funeral on a two manual pipe organ which most people consider has a powerful sound. The lady being laid to rest had been a notable producer of Gilbert and Sullivan operettas, so the choir was appropriately drawn from singers who had participated in her productions. We had eight each of sopranos, altos, tenors and basses. When the choir sang double-forte – which was most of the time – the only organ stop that could be heard was the Great Tromba – the remainder of the organ was inaudible!
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Re: Audio equipment powered by different phases

Postby nazardo » Thu Sep 27, 2018 6:49 am

adrianw wrote:No, I understand why you might be concerned but I would not expect that to cause any audio problem.
organsRgreat wrote:There seems to be some confusion here between the phases of audio signals, and those of the mains power supply; but I cannot see that the two would be related. For mains power to be used by an amplifier it needs first to be rectified, and DC power, being continuous, cannot have a phase.

Thank you, that is what I expected.

adrianw wrote:However calculating the power demands of audio amplifiers for electrical supply purposes is not as straightforward as it may seem and your estimate of the total power demand (on which your electrician is presumably making his suggestions for phase distribution) might be unrealistic. If it were watt-for-watt, stadium concerts with their hundreds of kW of audio amplification would simply not be possible. You will be spending quite a bit of money and should get specialist advice.
organsRgreat wrote:the correspondence between mains power and speaker output power is not as simple as a one-to-one conversion.

I know that audio wattage is not (always) the same as electrical wattage. I took power consumption values from datasheets and product documentations. For Definitive Technology integrated subs, the retailer has told me to consider 300 W per tower as the internal Class D amplifier has an almost 1:1 power transfer ratio.

Of course I expect the effective power consumption to be much lower than the one obtained with my calculations, as all the equipment will not be run at its maximum ratings.
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Re: Audio equipment powered by different phases

Postby ppytprs » Thu Sep 27, 2018 7:02 am

In terms of balancing a building's phases, I would have thought 7kW pretty inconsequential, and not worth the bother of wiring across three phases. That, and the fact that you'll probably be actually drawing very few watts. However, if you're having this supply wired in specially, then the electrician should do it how he sees fit. If it's going to cost more to do it this way though, I'd perhaps try measuring the actual power draw of the kit.
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Re: Audio equipment powered by different phases

Postby nazardo » Thu Sep 27, 2018 9:32 am

ppytprs wrote:I'd perhaps try measuring the actual power draw of the kit.

Yes, this is a possible course of action. It would mean waiting for all equipment to get installed, have the electrician measure the actual power drain during a playing session, apply appropriate overhead to the power figures and finally design the power distribution.

Since we already have three-phase electric power (100 KW) in a near room, I think it would be faster to just lay down a 10KW connection and use that. If the power consumption of the new system will be much more lower, we could later reduce the rating of breakers and relays.
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Re: Audio equipment powered by different phases

Postby adrianw » Thu Sep 27, 2018 9:38 am

I know that audio wattage is not (always) the same as electrical wattage. I took power consumption values from datasheets and product documentations.


I guessed that you had. That is certainly safe, but not what is needed to determine whether you need 3 phase.

It is a long time since I was professionally involved in this, but you might find that an expert reduces this by a ratio of perhaps 8:1 (or more) when calculating typical AC supply needs. Your calculations are fine if you were installing space heaters: they do not work for calculating the real AC power supply needs of audio amplifiers. Although there is a need to consider peak power as well as typical power, it is typical power demands that will determine phase balancing.
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Re: Audio equipment powered by different phases

Postby nazardo » Thu Sep 27, 2018 10:07 am

adrianw wrote:It is a long time since I was professionally involved in this, but you might find that an expert reduces this by a ratio of perhaps 8:1 (or more) when calculating typical AC supply needs

I am really struggling to find out how to obtain the typical AC supply needs of my system. I asked many parties, but got no proper answer other than looking at figures in data-sheets.

Thank you very much to everyone who is contributing to this discussion. I think we are going a little bit off topic, as the conversation is moving from "will audio equipment work on three phase?" to "is my estimated power supply correct?". Nevertheless this second question is much more important to me now.

Do you have any advice on how to proceed? Is a direct measure on the installed system the only way to go or can I compute the typical value beforehand and set up power distribution in advance?
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Re: Audio equipment powered by different phases

Postby adrianw » Thu Sep 27, 2018 10:23 am

OK. Simple advice: IMHO you really don't need 3 phase. Although you might calculate a peak load equivalent to a couple of kettles, (itself hardly worth 3 phase), the actual peak load when playing to the point of onset of distortion will be considerably less and in normal playing all the amps together will probably draw about the same as the computer.

But you don't need to believe me, and you don't need to wait until everything is on hand to test. If you have any of the components to hand (a powered speaker maybe) you can measure yourself the likely ratio between the data sheet figures and the actual power consumption with full organ and volume wound to the brink of distortion.

None of this is a criticism of your electrician: unless he is experienced in audio installation he will assume the figures on your diagram are the actual continuous power demands and advise accordingly.
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Re: Audio equipment powered by different phases

Postby nazardo » Thu Sep 27, 2018 10:49 am

Thanks.

adrianw wrote:If you have any of the components to hand (a powered speaker maybe) you can measure yourself the likely ratio between the data sheet figures and the actual power consumption with full organ and volume wound to the brink of distortion.

Unfortunately I have no equipment at hand, I will have to wait.

adrianw wrote:None of this is a criticism of your electrician: unless he is experienced in audio installation he will assume the figures on your diagram are the actual continuous power demands and advise accordingly.

You are perfectly right, he has trusted my figures and considered them as a continuous power demand.
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Re: Audio equipment powered by different phases

Postby nazardo » Fri Sep 28, 2018 4:38 am

An update on the topic.

adrianw wrote:you might find that an expert reduces this by a ratio of perhaps 8:1 (or more) when calculating typical AC supply needs

I managed to reach out to some audio professionals and that is exactly the answer I got.

Image

One 2 kW line seems to be more than enough for my needs. As a future proof design decision, since it is a new installation, I will ask the electrician to bring three 2 kW lines to the organ balcony.
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Re: Audio equipment powered by different phases

Postby jkinkennon » Fri Sep 28, 2018 10:17 am

Any time you connect audio equipment on different circuits, whether or not they are different phases, it is doubly important to run balanced audio only to minimize hum and other noise. Any modern amplifiers will operate fine on different phases, not that this is a realistic issue in all but the largest of venues. Separate circuits might be needed in even a modestly sized public venue.
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Re: Audio equipment powered by different phases

Postby engrssc » Fri Sep 28, 2018 11:15 am

BTW, in N America, circuit loads are designated in Amps. Minor point.

(P=IE) Watts= Amps X Voltage.

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