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Balanced vs standard power

Searching for an Isolation Transformer 10 or 15kva. I have the budget for Equitech but I'm sold only on the benefits of isolation and not "yet" on the benefits of balanced power unless one is recording live musicians. My rationale is that most if not all audio components are not designed with balanced power so they may be optimal performers with standard power and lesser performers with balanced power. Until someone does a side by side comparing isolated balanced to isolated standard power we may never know.

I have read the various threads regarding isolation transformers from Equitech 10wq, MGE Topaz etc, and the Euqitech stereophile review. For larger non-balanced options there is Ultra K 600 with K factor correction and triple shielding from the Controlled Power Company. They range from 5 to 25 kva.

I think supersizing Isolation transformers for audio is not well recognized yet because no one has done the necessary review/ comparisons to determine the performance curve of Isolation Transformer size to Audio Performance. Although Isoclean advocates the use of two of their Isolation Transformers for each piece of equipment. Maybe they're trying to tell us something or just sell more transformers. 10 KVA is "plenty" for my system according to Martin at Equitech, but "plenty" is not quantified enough to convince me, so I 'm leaning toward the 15kva on the Ultra K 600 from Controlled Power about $4000 vs Equitech 15 kVA at upwards of $14000.
natan6355
jea48
4,296 posts
 
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
jea48
4,296 posts
 
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
norm's avatar
norm
52 posts
 
Thx Jea. You are correct. By adding capacitance to the secondary side this did raise the output voltage to approx. 1v. However, input voltage is still 2V higher than output voltage.

Hi Al,

Would you please elaborate how increasing the capacitance to the secondary side of the transformer may cause voltage to "lag"? Also, how much additional current is the transformer "pulling" by adding 220uf.

Best reagrds,

Norm
norm's avatar
norm
52 posts
 
Hi Jim,

Are you saying that by adding 220uf to the circuit I have effectively lowered my 10kVA xfmr rating to 5kVA?

Best regards,
Norm
almarg's avatar
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almarg
9,670 posts
 
03-11-12: Jea48
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.
Good point, Jim. Agreed.
03-11-12: Jea48
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?
Good question, which I had been wondering myself. I don't know the answer.
03-11-12: Norm
Would you please elaborate how increasing the capacitance to the secondary side of the transformer may cause voltage to "lag"?
The voltage across a capacitor cannot change instantly. It changes in response to the accumulation or depletion of the charge it is storing, which in turn is proportional to the integral of current, over time. As a consequence of that, for a sinusoidal AC waveform of a given frequency, and assuming an idealized capacitor model, and since the integral of a sine wave is an inverted cosine wave, the voltage across a capacitor will lag the current by 90 degrees, or 1/4 cycle.
03-11-12: Norm
Also, how much additional current is the transformer "pulling" by adding 220uf.
10 amps, based on the assumption that 120 volts is placed across the 12 ohm impedance which the capacitor has at 60 Hz.
03-11-12: Norm
Jim, are you saying that by adding 220uf to the circuit I have effectively lowered my 10kVA xfmr rating to 5kVA?
No, the capacitor has nothing to do with that, although the capacitor significantly increases the amount of current the transformer has to supply, and significantly increases how much of the 5 kVA capability is being utilized. Referring to the data sheet for the transformer, each of the two secondary windings is rated to handle 41 amps. Presumably you have them connected in series, with nominally 60 volts appearing across each winding, and 120 volts across the series combination. 120 x 41 = 4920 VA, or a little under 5 kVA.

Also, to make sure I'm envisioning your setup correctly, I'm assuming that the two 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?

Best regards,
-- Al
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