Hi Natan6365, I am looking for the Controlled Power co's Ultra K 600 isolation transformer and wondering if you can provide me with more details and share with me your impression so far. Thanks! Andrew
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.
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.
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03-11-12: NormHi 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 |
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 |
Are you saying that by adding 220uf to the circuit I have effectively lowered my 10kVA xfmr rating to 5kVA?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? 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 |
03-11-12: Jea48Good point, Jim. Agreed. 03-11-12: Jea48Good question, which I had been wondering myself. I don't know the answer. 03-11-12: NormThe 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: Norm10 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: NormNo, 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 |
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 |
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 |
Good points, but in no. 2 shouldn't "lead" be "lag"? 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 |
Jim -- Good points, but in no. 2 shouldn't "lead" be "lag"? 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! Best regards, -- Al |
By adding a 220uf capacitor to the secondary side of the transformer, 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. . |
I, also, recently joined the BP ranks. Im using a Signal DU-10 transformer wired for balanced power with electronics that can potentially draw a max. of 3400kVA. My findings with BP are similar to that of Zmanastroomy & Charles1dad. By adding a 220uf capacitor to the secondary side of the transformer, this made a HUGE improvement to the sound. The improvement with the added capacitance is far more impressive than BP alone, which was already a significant upgrade. The down side with the added capacitance the trannie generates more heat and noise. |
Natan6355, Hello and congratulations on your sucessful implementation of the balanced power (BP) transformer. Is the size overkill? I `d say yes (for home audio components) but absoluttely harmless(and hey, it`s what you wanted).Your results don`t surprise me but are what one would expect. As I wrote earlier in this thread my experience with a BP transformer (in use 3 years) has been a completely positive move 'without any downside'. The improvement was immediate and substantial, and when I tried putting the components back into the wall outlets(dedicated 20 amp service) the decline in sound is undeniable. I don`t understand what is 'debatable' about balanced AC power at this point. |
Well, I finally had Controlled Power co's Ultra K 600 isolation transformer (15 kva with triple shield and k 13 factor correction ) installed in front of the Isoclean Zero Ohm breaker panel. I have pics but unsure how to upload them here. The benefits were discernible immediately and performance continues to improve at 100 hrs currently. Oversizing did not hurt performance or create excessive noise as mentioned in this thread, and the results i am getting are nothing short of exhilarating. Unfortunately, I can't comment if its better than 10 kva or 5 kva since I don't have these on hand. However, since the size of the exterior of these units are very similar and the weight varies by roughly 150 lbs from lowest to highest and the cost variation is not significant, 15kva @$3700 vs 10kva @$2900 vs 5kva @2700, I would say opting to oversize is a no brainer. I am convinced that whether you live in the city, or in the country as I do, whether your sharing the grid with multiple neighbors,or just a few as I am, that an isolation transformer is one of those audio purchases that is so satisfying that the monetary investment becomes a pleasure rather than a burden. Honestly, I think some would pay a lot more than $3650 to get this kind of performance upgrade. But Controlled power has no idea of this, yet. And I'm sure some savvy audio dealer may eventually get them to tweak their design with audio applications in mind. So while the balanced vs standard power debate rages on, I am thrilled with my current set up. |
I will say that, in a way, I envy your overkill of this power system. Most people seem to think that a plug in surge protector will do the job. The way that you have implemented the devices, i.e. not having them close to the HT/audio systems, is absolutely correct. I can't tell you how many times I have owned devices that made more physical noise than the electrical noise that they were trying to eliminate in the first place! I took my situation as far as I could by having the secondary feed to the house replaced, as well as having three other houses replace theirs too. We all fed off of the same transformer. Then I replaced an old panel with a decent Square D panel. Then I ran a 10 Ga. dedicated line to the audio system. And finally, I use a BPT balanced device that uses 8 different secondary windings to help isolate one section from the other. Did it help, you bet. I am eager to see what positive effects that your method adds. |
Thanks for all the advice. I am still leaning toward 15 kva Isol trans due to the size of my system. I have a dedicated 100 amp service from the electric company transformer feeding a dedicated 9 circuit/ 80 amp isoclean breaker panel. This service shares the same power meter with 2 other 100 amp services feeding my 2 household breaker panels. I have 3 systems fed by the isoclean breaker panel which includes hometheater with projector, processor, large multichannel amp, 3 powered subs, multiple sources, housewide music distribution with 1 large multichannel amp and 1 large stereo amp and multiple sources, and finally 2 channel system with 1 amp, 4 powered subs, digital, vinyl, reel to reel sources, main preamp and phono preamp. Also several large plasma screens. In the future I anticipate more computer based sources and processors, more amplifiers and more screens and possibly a 4th system. during the summer and fall I usually have 2 systems working simultaneously. Winter and spring usually 1 system at a time. On rare occasions all 3 are going. All electric services come in through my garage which is the location of my isoclean breaker panel. The 450lb ultra k will be installed in the garage immediately adjacent to the panel. This location is completely isolated physically from all systems. |
Jea48 THANK YOU! GOOD LORD, why don't we just hook a dedicated line from a substation. There is no doubt that this 15KVA is an overkill idea. I used to work with dc current 60-1,200 amps. requiring less than 1/4 voltage drop. For that kind of specification, we sometimes used cables as big as you'r wrist!(750kcml). I don't doubt that they engineered these battery circuits for very specific purposes. So when I see consumers buying bigger is better thinking, I know that there is an uneducated/greedy salesman lurking in the shadows. Yes, there is a great need for clean power, and balanced power is very effective for cancelation of noise. Yes, there is a need for adequate reserve, but don't you think that a DECENT piece of equipment(such as Levinson) considers that in their design? No doubt you should have low impedance, and the best(read tight) connections required. Yes can analyze this to death, but in the end, your ears are to be the judge and not some hype/misinformation. |
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While I see the benefits of having one large primary isolation transformer for separating your main audio line from the rest of the house and regional power. but, you still have noise generated and kicked back into the line by individual audio components, especially those with switching power supplies. So, you may want to isolate individual components from each other. Obviously, amps need much larger transformers than sources. I bought six surplus commercial/industrial Topaz 2.4kVA Ultra-Isolator Transformers. It was actually a 240V, 3-phase, setup that I simply separated into individual units and re-wired for balanced power operation. Anyway, it is amazing how much line noise you don't notice until it is gone. |
For the record, I just noticed what appears to be a boo boo in the paper by Mr. Whitlock of Jensen Transformers. In figure 2, which I referred to earlier, the formulas for Vx and Vy should have CPS1 and CPS3 in their numerators, respectively, rather than CPS2 and CPS4. That follows from the fact that the voltage divider effect between the two capacitances in each component will be dependent on the reactance of the capacitors (1/(2piFC)), not on the capacitance values themselves. Therefore I retract my previous theory about CPS4 of the unused amplifier causing Vy, and hence the hum level, to worsen. Best regards, -- Al |
The cost of the jensens and the fact that they will impact the sound doesn't make that an attractive long-term solution. I guess I'll just byte the bullet and send these off to get fixed the right the way. Can't blame a guy for trying to find an easier solution, but in the long run, there is only one way to fix this correctly. I know my guy can fix this since he's been marketing his own monoblocks for a year now. He'll be shocked I'm finally sending these amps to him since he's been after me for a while now. :-) |
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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.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 |
Dan-ed - All connections back to and inside the incoming ac panel have been verified for tightness? Wire routing is according to hoyle, etc.? I suspect that you have checked all the basics but, just in case. The weirdest hum issue I've had (2 arcam alpha 10's, 1 would hum whenever plugged in the other 1 never hummed, nothing else plugged in to the same circuit showed any sign of a problem) went away for good when I tightened all neutral connections at my incoming breaker panel. At least I assume it was due to a neutral connection because no other connections seemed suspect. Arcam's tech said on the phone that it was an ongoing frustration for him at the time, some units would hum at customers site but not hum in shop, some units would not hum. |
Nothing about the Equitech article implies any kind of panacea. In fact, if it's a ground issue, even separately isolating each amp might not help. Perhaps Jim or Al can comment on the issue of UL/CSA standards and shunting/grounding as compared to IEC. I gotta step back and listen when those guys are talking. |
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.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. 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 your interpretation. I believe I have the "extremely rare" occurrence mentioned in the Jensen paper. :-) I realize this probably won't eliminate all of the hum, but cutting it in half might make it liveable. I'd like to put each of these two amps on their own balanced supply. These are around 60 watt PP amps so I don't need too large of transformers. Maybe a pair of 500va on each. Finding them for an experimenting price might take some looking. |
Hi Dan, I read through the Equitech paper, and it strikes me as excellent. However, it also strikes me as not inconsistent with the comments on balanced power in the Jensen paper, which is to say that there would probably be significant hum reduction if you used a balanced power arrangement, but not necessarily a reduction that is fully satisfactory. From the Jensen paper: It is also very unlikely that the two capacitances, CPS1 and CPS2 or CPS3 and CPS4, would be exactly matched in any piece of equipment. Mismatch ratios of two to one are common.... Although intuitively attractive, [the balanced power] approach can completely cancel interchassis currents in a system of three or more devices only in the case where each of the devices had such matched capacitances. This would be an extremely rare occurrence.... 10 to 15 dB hum reductions ... would be more routinely achieved.From the Equitech paper: If any aspect of the circuit is applied OR LOADED [emphasis added] in an unbalanced manner, noise will appear in the ground.... On the average, 16dB improvement in background noise has been noted.In other words, any difference between the stray capacitances CPS3 and CPS4 in your particular amplifiers (which is unpredictable) will limit the amount of hum reduction balanced power would provide. In considering the 10 to 16 db numbers, keep in mind the rule of thumb that a reduction of 10db is subjectively "half as loud." Best regards, -- Al |
Yes, all unbalanced. I put the two tube amps on cheaters. When they are both off I see about 2.5 vac and that drops to about 1.3 vac when both are switched on. That seems to go along with your theory, Al. I have also been referencing this paper from Equitech's web site. Lifting the Grounding Enigma They seem to be saying that the balanced power approach will do the trick for my situation but I can't reason it out. |
Just having one of the other amps plugged in but not turned on or connected in any other way is enough to cause the hum.Wow! That's different! When the amp that is not connected to anything except power is turned on, does the hum get better, worse, or stay the same, compared to when it is turned off? A possible explanation that occurs to me is that, referring to Figure 1 of the Jensen paper that Jim and I both linked to (great minds think alike :-)), when you plug in the unused amp, and it is in the turned off state, you are placing CPS4 (as defined in Figure 1) of the unused amp in parallel with CPS4 of the amp or amps that is/are being used. That would worsen Vy (as shown in Figure 2) for the amp(s) that is/are in use, thereby worsening the ground loop situation between the amp(s) being used and the preamp or whatever is driving it or them. If the amount of hum decreases when the unused amp is turned on, it would add credibility to that theory, because doing so would place CPS3 of the amps in parallel, as well as CPS4, which would to some degree reduce the effects of the increase in CPS4. I presume, btw, that the preamp to amp interconnections are unbalanced, as I would expect these kinds of effects to be much less significant with balanced interconnections. Best regards, -- Al |
Jea48, I run them from the same wall outlet. So I have 2, really three with the SS bass amp, grounded devices on the same circuit. It is the best case, but I still get potential between any two of the amps. Individually, they are dead silent. I do suspect the issue is zero reference between the two, tube amps. Hi Al. Thanks for tuning in cuz I'm just about over my head. :-) The Jesen paper is very good reference. Only difference is I think this is on the ac lines. Maybe I'm misinterpreting things. From my experiments, I get this hum regardless of interconnections between the amp inputs. Just having one of the other amps plugged in but not turned on or connected in any other way is enough to cause the hum. Still, it is cheap enough to try the audio isolators on the inputs. That may help convince me if more power side treatment will work or not. |
11-06-11: Dan_edHi Dan, 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. Best regards, -- Al |
I think I get it, but see what you guys think about this. My two amps hum because they reference ground at a slightly different potential, and that creates a small current between them when they are on the same circuit. The balanced connections assure that all components plugged into it reference the same ground so there would be no potential between the amps. Yes? No? Smoking crack? :-) |
I'm interested in balanced power, and I have a question I hope you guys might now. I have two amps that I like to run together, but the hum like crazy when both are plugged. I know the issue is because one, or both, are not wired in common mode. I have been reading some papers on the Equitech web site about this issue and they claim balanced power will solve this problem with no equipment changes needed. Not that I dispute their claim, but I'm having a hard time understanding how it would clean up the ground circuit after current has entered from down stream. What do you guys think? Would balanced power connections safely isolate these amps? |
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 . |
Interesting question about the harmonics. Personally have doubts about any kind of harmonic filtration below 1 KHz for any passive technology, not including regeneration, but I'm not an expert and ferroresonance has it's mysteries. Don't have an oscilloscope to do any testing either. Shared this link before with the caveats of the author affiliation and date. http://www.contractorsav.com/article/2006/11/07/ac-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. 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. . |
Ngjockey - Thanks for the response. I understand that the sola is not just a transformer:). 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. Perhaps not an issue at all but since the topic is about getting very nit picky with incoming ac it may be a nit worth picking. Oh, for what it is worth I've never seen $20.00 per unit but I think you can find them reconditioned for about 50% price fairly regularly. No response necessary unless the mood strikes you. Just pondering. |
Wish it were that simple but there's more to those than just a transformer. As part of the ferroresonant design, they are partially saturated at all times. Along the same lines, in regulating voltage, amperage can suffer. So... with a dynamic load, they have to be oversized to a larger factor . While the CVT series has better amperage stability and tighter regulation, they're more like autoformers so noise reduction is one third of the MCR and a true isolation transformer. Don't get me wrong, for decades they have been the 'king of the hill' as far as fast, reliable regulation and only recent, advanced electronic tap switchers can compete for the throne. They're also heavier and expensive, except for that used, $20, 1000W MCR portable I bought once. |
