Balanced vs standard power

I'm curious about how incoming line harmonics would compare between a system with electronic tap switchers vs a sola system, maybe not an issue unless the o.p. went with multiple smaller units that could potentially be 'talking' to each other or had other sensitive non-stereo electronics on the same ac line.
11-04-11: Jeff_jones

Jeff_jones,

Most of the odd harmonics found on the AC mains of our homes is from nonlinear loads connected to the mains within our homes. The home computer being one of the worst.

>http://www.pge.com/includes/docs/pdfs/mybusiness/customerservice/energystatus/powerquality/harmonics.pdf


>http://www.emersonnetworkpower.co.in/KnowledgeCenter/Whitepapers/K-FactorTransformer.pdf


Natan6355 is looking at a K rated 15 KVA transformer.

K rated transformers
>http://www.powertransformer.us/transformerarticles/transformerkfactorrating.htm


JMHO a 15 KVA transformer is overkill. He will have to feed that beast with #3 copper wire connected to a 2 pole 80 amp breaker, minimum, (125% of primary FLA). (240V single phase.)

Because there will be next to nothing of a connected load more than likely it will be mechanically noisy and very inefficient.....

A power utility pole transformer in older residential neighborhoods that feed 4 or more homes is only a 25 KVA transformer on avg. Pad mounts a 50 KVA on avg.
.

Here are the links I posted above.
http://www.pge.com/includes/docs/pdfs/mybusiness/customerservice/energystatus/powerquality/harmonics.pdf

http://www.emersonnetworkpower.co.in/KnowledgeCenter/Whitepapers/K-FactorTransformer.pdf

http://www.powertransformer.us/transformerarticles/transformerkfactorrating.htm
.

Dan_ed

Just curious have you ever checked the two amps for the proper AC polarity orientation?
http://www.boundforsound.com/tweak.htm

Ground loop hum.
http://www.jensen-transformers.com/an/an004.pdf

See the second paragraph of page 2 of this Jensen paper. A key factor in how much hum reduction would result is the stray capacitance within each component between each of the two ac input lines and chassis, particularly stray capacitance in the power transformers of the components, and how similar or dissimilar those stray capacitances happen to be. So while I would expect there to be SOME improvement, the amount of improvement figures to not have a great deal of predictability.
11-06-11: Almarg

Al,

My thinking as well.

>>>>>>>

I took some measurements from each amp using the ground tab on a cheater plug with nothing turned on, just plugged in. I'm seeing 16 vac on the ground tab from one tube amp and 14 vac on the ground tab with the other tube amp. The SS amp shows no potential. I didn't bother measuring the ac current.
11-06-11: Dan_ed

Dan_ed,

If you are checking for the proper AC polarity orientation of the primary winding of each amp's power transformer nothing can be connected to the input of the amp/s. Also equipment ground of the amp/s has to float. (Amp is isolated)

The ground cheater you use needs to be the non polarized plug type or you will need to trim down the wider blade so you can reverse the plug in either direction.

The lower measured voltage reading is the correct polarity orientation.

Post back your results.

http://www.audioasylum.com/audio/general/messages/449743.html
.

Thanks for the help, guys. Jea48, even if I did that it can't be maintained with a three prong connector. Yeah, the best solution would be to pack them off and have them rewired to play together. I hate shipping them as one already has chassis damage from mishandling.
11-07-11: Dan_ed

Dan the polarity orientation check is only a test to make sure the manufacture of the amp checked for proper polarity orientation of the primary winding of the transformer before it was wired to the circuit.

If the test shows one of the amps power transformers has reversed polarity the next step is to check the power cord, if detachable IEC connection, and make sure the polarity of the cord is correct. Especially in the case of an aftermarket non UL or CSA listed power cord.

Next step if the power cord/s checks ok and the problem is the amp I would then try a real word test of the system and check for the ground loop hum.

Remove the ground cheater on the good amp. For the test the amp that needs the polarity reversed install the ground cheater into the wall outlet that gives the lowest voltage reading of the two.

Next connect the ground of the cheater to earth ground. (equipment ground at the wall outlet).

Turn system on and check for hum. IF hum is gone then the next step is to correct the problem.
The correct procedure is to reverse the primary leads connection inside the amp. Who better to do the job than the manufacture. Good chance he will only charge you for shipping.

You could also take the amp to a reputable repair tech.

There is no guarantee the hum problem is caused by a polarity reversed orientation. The test will require a little of your time and hopefully find the problem.

Or you could just buy a Jensen isolator for one or both ics.
Contact Jensen, bet they would be glad to help.
Jim

By adding a 220uf capacitor to the secondary side of the transformer,
03-10-12: Norm

Norm,

A word of caution when adding capacitance in an AC circuit.
Two things that can happen.

(1) The capacitor can raise the output voltage.

(2) Too much capacitance causes the voltage to lead the current causing a leading power factor. Result is a low power factor.... That can cause overheating of the secondary winding of the transformer.
.

Good points, but in no. 2 shouldn't "lead" be "lag"?
03-10-12: Almarg

Al,

You are correct....

Should read
Too much capacitance causes the voltage to "lag" the current causing a leading power factor. Result is a low power factor....

Re the 220uf, that corresponds to an impedance (capacitive reactance) of 12 ohms at 60 Hz. That will certainly pull a lot of current through the transformer, but I suppose it's within reason given the 10 kVA rating of the DU-10, and the 3.4 kVA load. Assuming the breakers and wiring can handle it all, of course!

Norm has the transformer configured for balanced power. That cuts the KVA rating of the xfmr in half.
The xfmr maximum continuous FLA rating is 5 KVA.

Jim

Al,

Just wonder if the poor PF, caused by too much capacitance on the AC line, is doing anything to the power xfmrs and switching power supplies of his audio equipment.

You are the EE here.... What say you?

Jim

Are you saying that by adding 220uf to the circuit I have effectively lowered my 10kVA xfmr rating to 5kVA?
03-11-12: Norm

Norm,

I agree with Al's explanation.

Not sure why the manufacture shows 41 amps FLA for each winding instead of 41.67A.... 5000 Va / 120V = 41.67A.
Could be the size of wire he used for each winding. Or maybe he just rounded the number down.
I am just guessing he used # 8 copper wire.

One thing for sure the specs given are for the nominal input and output voltages shown on the data sheet.
Without actual load testing the power the xfmr could deliver under full load, configured for 60/120V, is unknown. Remember you are halving the voltage fed to the primary of the xfmr. 60V across each winding.

JMHO,....
I would have configured the xfmr primary for 240V and the secondary for single phase 120V out.
The full 10KVA rating of the xfmr could then be utilized.
FLA rating would be 82 amps instead of 41 amps. Your power amplifier will appreciate it.

Ditch the 220uf capacitor and the added cost of the wasted electrical power it is consuming.

Also, to make sure I'm envisioning your setup correctly, I'm assuming that the primary windings are connected in series, and are fed by a single-phase 120V line and breaker rated at 40 amps or more. Is that correct?
03-11-12: Almarg

Al,

Per NEC code the minimum would be 125% of the xfmr name plate FLA rating. 41 x 125% = 51.25 amps, roll up to a 60 amp breaker.

If the secondary of the xfmr has overcurrent protection the primary overcurrent protection can be as high as 250% of FLA rating.
Jim