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
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
Hi Al,

Thx for your thorough explanation.

A 2 x 20 amp breaker tied together a single=phase 120v line is feeding the Primary windings of the xfmr. The Secondary side of xfmr is also connected in series. Thus, -60V/+60V.

Would you care to take a guess what is happening to the electronics(tube gear) with voltage and amperage being 1/4 cycle out? The overall results with the additional capacitance is a big improvement, especially LF.
Am I doing any damage to my xfer and/or electronics by the additional capacitance?

Best regards,
Norm
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
Hi Jim,
Currently the xfmr is configured for Balanced powered, -60V/+60V, to reduce unwanted noise by CMR (by 10-12 db?). If I were to, configured the primary for 240V and the secondary 120V out, as you suggested, would I not be using the DU-10 as an isolation transformer as opposed to BP? If this is the case, what are the pro/cons, besides doubling the amperage capacity from my present set-up?

Best,
Norm
03-11-12: Norm
Would you care to take a guess what is happening to the electronics(tube gear) with voltage and amperage being 1/4 cycle out? The overall results with the additional capacitance is a big improvement, especially LF. Am I doing any damage to my xfer and/or electronics by the additional capacitance?
Hi Norm,

As I indicated earlier I don't really know, as my technical background is not specifically relevant. I will say, though, that it does strike me as plausible that there could be SOME risk over the long term, but I don't have much if any feel for how significant it might be.

One mechanism that occurs to me by which a problem could result is if a resonant frequency that is formed by the interaction of the capacitor and the inductance of the wiring and/or the transformer were to happen to coincide with a frequency component of either a transient on the power line or a harmonic distortion component that may be present on it (perhaps created by the amplifier's power supply, or by something external to the system), the resonance could conceivably boost the magnitude of that transient or distortion component to very high and potentially damaging levels.

As I say, though, I don't have any particular instinct for how significant that or other risks may be.

Best regards,
-- Al