Efficiency of Sola Constant Voltage Transformer?

Don't know why you weren't able to find this:

Manual for the model you're interested in. The answer may be in here:

They are still pretty inefficient. Don't think the technology has changed since day one. But boy do they work good, especially the CVS (1%) series!

Steve Noll | The Used Equipment Dealer Directory: |

clean

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I wouldn't.

inspection

I'd be more worried about the output waveform esp. during any power outage situation. I'd certainly run the idea past the UPS maker first. I suggest you get APC to re-engineer a solution for you.

I did a Google search and it took me to a web site with an almost identical name that wasn't Sola's web site. I hate those copycat domain names, trying to steer legitimate business toward spam sites. Anyway...

Thanks for this link. I think page 12 summed it up, by mentioning that the input current will be 50% of the full load current, even if no load is present. So that suggests that it's wise to get the right size CVS, not an oversized one!

-- Best Regards,

Mark A. Weiss, P.E.

manufacturer,

Google found me this link sola-heavy-duty.com which is a spam-infested mess and NOT Sola's site. Thanks for the correct link.

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Too costly. I bought the UPS as a refurbished unit. I'm shopping for a used CVS on Ebay. I have hundreds of dollars to spend on this, not $30,000+ for a reengineered solution.

My testing has verified that our problem is not generator frequency, but harmonics. The UPS sensitivity can be lowered, but then when it switched, several computers on the network reboot. Only in the High sensitivity position does the APC UPS switch fast enough to avoid rebooting computers on the network. Although on the setting below High sensitivity, the UPS is happy on generator power. Only problem is we have stuff rebooting when it cuts over. Hence, we must run in the high sensitivity mode of the UPS and clean up the input power with the Sola CVS.

-- Best Regards,

Mark A. Weiss, P.E.

"Bennett Price" wrote in message news: snipped-for-privacy@itsa.ucsf.edu...

My biggest concern is becoming one of whether this will vastly increase our electric consumption. I read some documentation that suggests that a 2kVa CVS will pull 1kVa at no load! They are most efficient at 100% load. So even though this would be going in front of a 2.2kVa UPS, our load is about 10 amperes on that branch, so I chose to get a 1kVa Sola 23-25-210 model, used, for $45, with the intent of loading it fully to maximize efficiency. Another thing mentioned in the docs is heat. They are designed to run so that the core is too hot to touch! That means more a/c load to cool the room. Lots of things to consider. But the used CVS is cheap enough so that if it doesn't give the results we want, we haven't lost $1700 that a new one would have cost. I'm very surprised that a desk lamp would not start. It must have had a high inrush current. That IS a concern with the Sola, as they fold back, and one PC power supply alone has a 80 ampere inrush current. Hopefully the CVS can handle that short spike before the field collapses and recover transparently. We'll see. The concern is more one of switching loads. But it may not be sensible to shut off unused PCs on the network once the CVS is installed, since the line current will be pretty much constant regardless of load on the CVS. Alternatively, we just modify all PC power supplies by adding a humungous DC input cap after the bridge rectifier, to increase the holdout time long enough so that we can use the "less" sensitive setting on the APC UPS, which slows down switching from line to UPS. Several pieces of equipment need modifying in this manner. A few seem to be okay with the momentary interruption in power as the UPS switches to online mode. Ultimately it will be an experiment.

-- Best Regards,

Mark A. Weiss, P.E.

about 10

that the

Besides the heat build up, keep in mind that they are noisy beasts and you really do not want one sitting next to you in a quiet working area. What maybe a little bit more efficient is a automatic-variable transformer in your amp range. Those are also great as line spike absorbers, etc.. and not as noisy, unless one set the auto-adjust to sharply.

Yes, saturated core transformers BUZZ and get hot, even under no load. They are not nice things to have around.

Note 1 KVA is not necesserily = 1 kW. At no load a good deal of that is reactive power but still enough true power to get the core hot.

Are you sure it is harmonics that are triggering your UPS?

Mark

You may not like this solution, but:

I've never tried this, but how about just opening up each computer power supply and replacing the input bridge filter capacitors to give the power supply more "ride thru" time? You might also want to upgrade the input rectifier diodes to survive the larger turn-on surge.

Doing this should allow you to run the UPS at a lower sensitivity setting and still keep the PCs on line. Plus, I don't think it would affect your efficiency at all.

Does this make sense, or am I missing something obvious?

Oops, I've read on down the thread and see that you've already considered this option. I think the hardest part about it would be finding new caps that fit in all the different PC power supplies. If the PCs are all alike then this becomes pretty easy. I don't think you really need to find caps more than 2x larger to make a pretty significant difference.

----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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You mean like the TrippLite LC2400? I had one of those and all it did was create a 'bounce' effect that resulted in the UPS starting up, shutting down, causing the LC2400 to switch taps, which caused a spike that the UPS thought was a line fault, triggering another cycle of UPS coming online, ad infinatum. Plus the LC2400 injected so much trash back into the line that other connected equipment on that branch got damaged.

It has to be a transformer, but no tap switching.

-- Best Regards,

Mark A. Weiss, P.E.

I have confirmed that it's not line frequency that's triggering it. So it has to be harmonics, of which there are a lot. The waveform looks like a squared-off ragged sine wave. I can lower the sensitivity, but then the PCs reboot in the time it takes to transfer from line to UPS.

-- Best Regards,

Mark A. Weiss, P.E.

It is likely that I will resort to this. I am also in the process of replacing old, inefficient Antec PSUs with more efficient Seasonic PSUs that are PF corrected. If that doesn't solve the holdover time, I may resort to modifying each PSU. Most PSUs have 680uF/200V caps in the bridge circuit. If I could find larger ones, or just tack some larger caps across it, that may do the trick. However, I also must modify some musical instruments that are resetting on this UPS. But that may be simpler. I think they use linear PSUs. Schematics are harder to find as they are proprietary protected property of the manufacturers.

-- Best Regards,

Mark A. Weiss, P.E.

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I don't know about TrippLite's but one 35 amp unit has been in constant use here for over 17 years without a hint of a problem.

Okay, no sense looking up the manufacturer then.

You know that most computer PSU have a bridge rectifier directly on the AC input, so I am not even sure what all the fuzz is all about.

A good AC filter block is all you really need in front of a UPS, that is, if the AC voltage is within the UPS range.

------ "Thank God it's Friday, only two more working days until Monday."

you may find that if you switch to power factor correct power supplies, the harmonics go away.

Question...

Does the generator create harmonics when feeding a resistive load or does the generator create harmonics only when feeding non power factor corrected loads.

The bridge rectifier capcitor inputs to many power supplies, conduct and load the generator only during the peak, and this can create the clipped waveform and harmonics that you describe. PF corrected supplies will (should) not do this.

Mark

Daft question - why not use an on-line UPS?

Dave

I'm sure that they have their appropriate uses, but one of them is NOT in front of a UPS.

The fuzz is from the generator. At default (high) sensitivity, the UPS triggers a transfer to battery when it sees the hash from the generator. I tried throwing some oil filled motor start caps across the line, but they had no effect. Something more radical, such as a CVS with harmonic neutralization is needed here. What sort of AC filter did you have in mind? The generator output looks like a badly clipped sinewave with jagged steps. Cleaning that up will take MAJOR filtering.

-- Best Regards,

Mark A. Weiss, P.E.

These harmonics are from the generator, not the load. At the time, we had about 5kW of air conditioning load on the genset, but the waveform is pretty consistent with various loads.

It's just dirty in general. Think of a motor with brushes. The field coil has brushes. That probably has a lot to due with the way the ac power looks.

Yes, but this would have an infinitessimal effect. I'm going with the higher capacity supplies that are PF-corrected not only to reduce operating costs, but because it will probably have a longer holdout. I still have to come up with a strategy for the Kurzweil PC2R, which uses a combination external 14VAC/9VDC transformer and who-knows-what for rectification and smoothing inside the unit itself. I'm also going to experiment with a used Sola 1kVa CVS that I bought on eBay for $45 this week.

-- Best Regards,

Mark A. Weiss, P.E.

Cost, heat, cost of operation. We have an offline UPS at present that we just invested in, replacing a 15+ year old ferro UPS.

-- Best Regards,

Mark A. Weiss, P.E.

(Google for "active tracking filters")

Always try to get rid of the interference right at the source. So buy a heavy duty Sola CVT for the generator so it can handle the current. The rest is all patch-work. There is no free lunch while doing business, less one receives a forgivable government grant, everything cost money. So you'll have to throw some real money into it or learn to live with the situation the way it is....