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Author Topic: Balanced Power Questions  (Read 9507 times)

Jeff Bankston

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Re: Balanced Power Questions
« Reply #10 on: November 25, 2013, 01:52:50 am »

Just out of curiosity I looked up one of the Furman units mentioned... $2500, 3 rack units, and 90 lbs for 20 amps of balanced power. On the bright side there's a convenient front mounted USB charger so you can charger your phone with it.  ;D
PHONE ?! I DONT NEED NO STINKING FONE ! OR BADGE !  :o
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Jerome Malsack

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Re: Balanced Power Questions
« Reply #11 on: November 25, 2013, 08:38:56 am »

One of the problems associated with balanced power is that the standard on and off switch in most gear is one pole. 

It is designed for the normal standard power configuration. 

The Navy with the balanced power on the ships requires power switches to be two pole and to open and close on the hot and the neutral/common.  Leaving the ground connected. 

The one pole switch will leave a neutral of 60 volts running to ground if the transformer has a center ground tap. 
Switching power supplies that have no tranny???

So Go for the further review and test on the switching and see what it puts out. 
Same for the tranny with the center tap . ?? 

I would like to see where this goes because I have not heard from anyone testing on this side with balanced power.

When I was on the ship I had the my electronics modified to include the two pole switch.  along with fuses on hot and neutral sides. 

 
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Steve M Smith

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Re: Balanced Power Questions
« Reply #12 on: November 25, 2013, 10:30:40 am »

Just about everything I have seen built since about 1980 has a double pole mains switch.


Steve.
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Jerome Malsack

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Re: Balanced Power Questions
« Reply #13 on: November 25, 2013, 11:47:55 am »

When looking at the simple computer power supply there appears to be only a single poles switch. 

http://www.pavouk.org/hw/en_atxps.html        sample schematic of power supply.

With the digital boards and amplifiers stating to use this technology  it does not look good for use on balanced power.
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John Roberts {JR}

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Re: Balanced Power Questions
« Reply #14 on: November 25, 2013, 12:18:56 pm »

One of the problems associated with balanced power is that the standard on and off switch in most gear is one pole. 
While the power switch will function fine, the larger issue is may be that the mains fuse will generally just disconnect one leg.  Arguably this is only a safety issue if there is a fault in the transformer primary winding. It is not acceptable to fuse the neutral mains lead, for normal power. 
 
Quote
It is designed for the normal standard power configuration. 

The Navy with the balanced power on the ships requires power switches to be two pole and to open and close on the hot and the neutral/common.  Leaving the ground connected. 

The one pole switch will leave a neutral of 60 volts running to ground if the transformer has a center ground tap. 
Switching power supplies that have no tranny???
nope, switching supplies have small HF transformers, while there may be some circuitry on the hot side of that transformer.
Quote
So Go for the further review and test on the switching and see what it puts out. 
Same for the tranny with the center tap . ?? 

I would like to see where this goes because I have not heard from anyone testing on this side with balanced power.

When I was on the ship I had the my electronics modified to include the two pole switch.  along with fuses on hot and neutral sides.
And hopefully you bypass those neutral fuses when on shore power.  It seems like an optimal re-settable circuit breaker would have a common bi-metallic actuator heated by both neutral and hot currents, so both contacts always open synchronously. Not a trivial or cheap mechanical design to tool up. 

JR

PS Balanced power seems like too much hassle for too little benefit.
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Jerome Malsack

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Re: Balanced Power Questions
« Reply #15 on: November 25, 2013, 12:45:45 pm »

While the power switch will function fine, the larger issue is may be that the mains fuse will generally just disconnect one leg.  Arguably this is only a safety issue if there is a fault in the transformer primary winding. It is not acceptable to fuse the neutral mains lead, for normal power. 
 nope, switching supplies have small HF transformers, while there may be some circuitry on the hot side of that transformer. And hopefully you bypass those neutral fuses when on shore power.  It seems like an optimal re-settable circuit breaker would have a common bi-metallic actuator heated by both neutral and hot currents, so both contacts always open synchronously. Not a trivial or cheap mechanical design to tool up. 

JR

PS Balanced power seems like too much hassle for too little benefit.

Those units are not in service.  One was a 1964 Scott tube amp that had a filter capacitor shorting to the pin 1 ground. 
I have not completed the tear down and repair on the power supply and filter capacitors. multi section  75 uf at 600 v.
« Last Edit: November 25, 2013, 01:13:42 pm by Mac Kerr »
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Greg_Cameron

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Re: Balanced Power Questions
« Reply #16 on: November 25, 2013, 03:40:23 pm »

Jump to page 26 on this PDF to get Bill Whitlock's take on balanced power schemes. He wrote the paper for Middle Atlantic.

http://www.middleatlantic.com/pdf/PowerPaper.pdf
« Last Edit: November 25, 2013, 03:50:35 pm by Greg Cameron »
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Kevin Graf

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Re: Balanced Power Questions
« Reply #17 on: November 25, 2013, 03:53:01 pm »

That would be Bill Whitlock, now AES committee chair on EMI/RFI.

From his recent PowerPoint:

An Overview of Audio System Grounding & Interfacing
9/4/2012 page 201

Bill Whitlock

So-Called “Balanced Power”
• Properly called SYMMETRICAL power
• Has very seductive intuitive appeal
• NOT similar to balanced audio lines in any way!
• Uses transformer having 120 V center-tapped secondary
• Both line and neutral output blades are energized at 60 V
• Although advertising often implies endorsement, NEC seriously restricts
its use – because it’s potentially dangerous!
• ONLY FOR PROFESSIONAL USE
• NOT to be used with lighting equipment, especially screw-base bulbs
• MUST have GFCI at outputs
• Only technical function is to reduce leakage currents
• Leakage currents are trivial system noise sources
• Reported noise reduction generally less than 10 dB
• Any real benefit likely due to its clustered outlets
This is an example of “marketing gone wild” if ever there was one!


http://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf
« Last Edit: November 25, 2013, 03:58:26 pm by Kevin Graf »
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Jeff Bankston

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Re: Balanced Power Questions
« Reply #18 on: November 25, 2013, 04:51:36 pm »

Just about everything I have seen built since about 1980 has a double pole mains switch.


Steve.
all my QSC amps have a single pole switch.
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John Roberts {JR}

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Re: Balanced Power Questions
« Reply #19 on: November 25, 2013, 04:53:04 pm »

(Almost) Everything I've ever done was single pole.  A few odd ball switched secondary using 2 pole.

JR
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Re: Balanced Power Questions
« Reply #19 on: November 25, 2013, 04:53:04 pm »


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