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Old 9th May 2012, 09:38 PM   #1
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Default why not 3 phase?

This question is bugging me from time to time,
why shouldn't 3 phase powersupply be used for high end audio amplifiers?
Supposedly smoother DC could be achieved, seems quite reasonable.
Might some PA system be using this setup, I'm not realy into those.

Any opinion ?
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Old 9th May 2012, 09:47 PM   #2
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3 phase power is rarely available. You want "Y" and most is Delta. So the market would be tiny.
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Old 9th May 2012, 09:50 PM   #3
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Sure, three phase will provide for a lower ripple power supply, all things being equal. But reasonable it is not. To be done properly, you need either a three phase transformer, 3-single phase transformers, or 2-single phase transformers connected open delta. More iron equals more cost.

Then there is the issue of availability, which for US residents is less than 1% of the population. Utilities normally will not install a three phase service unless kW demand is a minimum value. Chances of getting three phase residential service is almost nil.

Better off with a bigger DC choke than using three phase. Permanently installed high power systems, such as auditoriums, churches, arenas, etc would be fine with it; I'm guessing most of those are 208V.
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Old 9th May 2012, 09:52 PM   #4
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Nothing wrong with delta; three phase rectifiers only require three legs- they don't use the neutral.
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Old 9th May 2012, 10:00 PM   #5
asmith is offline asmith  United States
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Default Some amps do.

Some of the BIG Crown amps do run on 3 phase. Seems like they made one rated for 10k RMS that had to be run that way.
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Old 10th May 2012, 01:15 PM   #6
AndrewT is offline AndrewT  Scotland
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I would expect PA equipment to come with the option to use or be adapted to 3phase supply.

I further suspect that some PA equipment only comes ready wired for a 3phase supply.
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Old 10th May 2012, 01:26 PM   #7
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MOD always use three phase.
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Old 10th May 2012, 03:29 PM   #8
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Quote:
Originally Posted by zigzagflux View Post
Sure, three phase will provide for a lower ripple power supply, all things being equal. But reasonable it is not. To be done properly, you need either a three phase transformer, 3-single phase transformers, or 2-single phase transformers connected open delta. More iron equals more cost.

Then there is the issue of availability, which for US residents is less than 1% of the population. Utilities normally will not install a three phase service unless kW demand is a minimum value. Chances of getting three phase residential service is almost nil.

Better off with a bigger DC choke than using three phase. Permanently installed high power systems, such as auditoriums, churches, arenas, etc would be fine with it; I'm guessing most of those are 208V.

1% ????
3 phase 16A / phase is the standard here, while i do agree that some residents to not have 3 phase wall connectors. Quite a surprise actualy. I was thinking USA people like dish washing machines and sortha stuff that requires 3 phase usualy.
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Old 10th May 2012, 04:31 PM   #9
jitter is offline jitter  Netherlands
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Ehm, if I'm not mistaken, residental buildings in the USA don't have the 3 phase system but the split phase system (Edison system) to get 110 V or 220 V.

See also this thread.

Last edited by jitter; 10th May 2012 at 04:33 PM.
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Old 10th May 2012, 04:40 PM   #10
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True, very few homes in the US have 3 phase power, only a few in mixed use neighborhoods even have the option.
8000 Volt 3 phase power entries my neighborhood, but only a single phase line goes down each street. Then a single phase transformer steps it down to 240 Volt center tapped.
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