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[Weogo Reed]

Hi Debbie,

Good question about modified vs 'pure' sine wave.
My understanding is there are modified sine wave variations that have very coarse steps, and
others that are closer to actual sine.
I believe an O-scope will show the wave form.
In my experience, the decent quality, modified sine wave units have (mostly)worked fine, though
you may hear some transformer buzzing when on battery.

Again, just my experience, but the bigger difference is whether you go double-conversion.
Particularly when running on a genny, this will separate the women from the girls.

I did a weekend lecture series at a camp on a big genny.  Every time the big freezer kicked in, the
old genny would groan, the little line-interactive UPS would go to battery, the
01V96 mixer transformer would buzz, and then a couple seconds later everything was fine.
The mixer had to sit near the presenters who heard the buzzing tranny.
I removed the UPS and the 01V96 capacitors carried the mixer through the genny ups and downs.
In this situation, a double-conversion UPS would have worked pretty quietly(except for the ones with noisy fans).

Remember, many of these UPS units are built for server-room type applications, and noisy fans aren't a big deal there.
And the fans probably aren't an issue for RnR shows either.

Thanks and good health,  Weogo

So how important is pure sine wave? I see this product doesn't have it. The one I am using right now does.....I like the lithium ion battery idea.

[Debbie Dunkley]

Hi Debbie,

Good question about modified vs 'pure' sine wave.
My understanding is there are modified sine wave variations that have very coarse steps, and
others that are closer to actual sine.
I believe an O-scope will show the wave form.
In my experience, the decent quality, modified sine wave units have (mostly)worked fine, though
you may hear some transformer buzzing when on battery.

Again, just my experience, but the bigger difference is whether you go double-conversion.
Particularly when running on a genny, this will separate the women from the girls.

I did a weekend lecture series at a camp on a big genny.  Every time the big freezer kicked in, the
old genny would groan, the little line-interactive UPS would go to battery, the
01V96 mixer transformer would buzz, and then a couple seconds later everything was fine.
The mixer had to sit near the presenters who heard the buzzing tranny.
I removed the UPS and the 01V96 capacitors carried the mixer through the genny ups and downs.
In this situation, a double-conversion UPS would have worked pretty quietly(except for the ones with noisy fans).

Remember, many of these UPS units are built for server-room type applications, and noisy fans aren't a big deal there.
And the fans probably aren't an issue for RnR shows either.

Thanks and good health,  Weogo

I have had a couple of occasions using very good quality diesel generators for shows but my UPS has not liked them at at all.  It will get completely confused and flash from 120v to battery and I have had to remove the UPS completely. However, when I use something like the Honda EU3000, Yamaha EF3000 etc, I get no problems with my UPS - it acts just like it does on power mains.

So.....you are saying that pure sine wave is not as important as double-conversion when it comes to UPS?

[Tim McCulloch]

I have had a couple of occasions using very good quality diesel generators for shows but my UPS has not liked them at at all.  It will get completely confused and flash from 120v to battery and I have had to remove the UPS completely. However, when I use something like the Honda EU3000, Yamaha EF3000 etc, I get no problems with my UPS - it acts just like it does on power mains.

So.....you are saying that pure sine wave is not as important as double-conversion when it comes to UPS?

Get a CHEAP inverter that plugs into your car's accessory power port (cigarette lighter) and try to power up the parts of your kit that will be on the UPS.  You'll find some things don't care much about the wave form and maybe other things won't work well or at all.  Which ones?  Hard to say.  I think 1 of our UPSs is modified sine wave and I don't recall any problems with the connected loads.

I suspect the bigger gensets you've been connected to have experienced frequency changes as the engine responds to changing load conditions.  Some UPS have more tolerance for input frequency, others are tighter.

Weogo's point is exactly why sometimes a generator needs a load bank to keep the genset running at a higher output (less revving up/down) when connected loading is low.

[Bob Leonard]

Pretty good points from you and Weogo Tim. Fact is that a UPS is not designed to hold up the hardware for any time more than it needs to gracefully shut the equipment down in the case of a power loss. Most hardware in my day world is either cabled to the UPS, or networked to the house backup system. Software is then applied to the OS and the grace period for shutdown is never much more than 10 minutes or less. In the case where the systems are located in a data center that would cover any period of time where the building generators fail to kick in. Any time a building generator(s) fail to kick in before 10 minutes are up makes for a very sad day for the people who own the building.

So the in rack UPS is actually a third failure point. The building generators, the battery banks, then your own UPS(S). After that it's call Mom and tell her you won't be home for dinner, breakfast, or even the next nights dinner.

In this world though the rack mounted UPS is a device allowing you to, as said previously, properly shut down the critical hardware in order to prevent OS corruption or component failure when the power surges back on. A decent UPS only needs to provide good clean power and 5-10 minutes of up time. and someone at the helm who is smart enough to shut down the console DSP, etc.. What does it matter if the powers gone? The show stops until it comes back anyway, and once back up you can bring the boards, etc. back up clean and on with the show. And again, buy good quality brand name hardware for the purpose. That means hardware that can be fixed in the USA, hardware that has batteries you can buy anywhere, and hardware that has phone support behind it.

[Robert Schoneman]

I've got some Eaton 5P 550's that serve me well.  They have two priorities of conditioned power.  The fans are audible, but not outrageously loud, IMHO.

Dave

We switched to the Eaton 5P 550's for all of our portable and installed gear after having grounding/noise issues with the CyberPower units.

[Joseph D. Macry]

Fact is that a UPS is not designed to hold up the hardware for any time more than it needs to gracefully shut the equipment down in the case of a power loss.

I have often seen a UPS specified for installed sound or paging system for schools where the paging is seen as a life safety system. The idea is to keep the system on for some length of time in case of power failure, so people won't miss the important announcements.

The problem comes when a medium or large amp is on the UPS, which often gripes at the inrush current when amp is first turned on.

[David Buckley]

I have often seen a UPS specified for installed sound or paging system for schools where the paging is seen as a life safety system.  ... The problem comes when a medium or large amp is on the UPS, which often gripes at the inrush current when amp is first turned on.

Yes, they do, don't they.  Any decent UPS will handle the inrush fine whilst utility power is present, perhaps beeping a bit, but if there is no utility power, then the UPS will fail to start the amp, and will just shut down.

This behaviour is a key part of how UPSs operate.

 A UPS is a wimpy thing, capable of supplying perhaps a 50% overload for a few cycles.

A big old amplifier with a big torroidal transformer has a huge inrush current, its almost a short circuit for a brief period of time.  So, when that amplifier is switched the UPS can't supply the (massive) current required. So what the UPS does is switches the output to utility power, which does have massive reserves, and the utility supplies enough current to get the amp going. Then a short while later the UPS switches back to inverter power for the load.

Obviously if there is no utility power then this strategy cant work.

[Dave Pluke]

So, when that amplifier is switched the UPS can't supply the (massive) current required.

Same goes for when housekeeping plugs a vacuum cleaner into a UPS (as our office cleaners sometimes did).  Had to tape the unused outlets over to discourage them.

Dave

[Joseph D. Macry]

When choosing a UPS for an installed system, the common question from the Owner is "How long will this model keep the system on?"
The answer, of course, is something like, "That depends upon how much you use it."
I never did figure out an accurate way to calculate that answer.

[Dave Pluke]

I never did figure out an accurate way to calculate that answer.

Can only truly be certain by running a test under full load.  And even then, realize that battery performance will wane from that original mark over time.

Dave

[ProSoundWeb Community]