Looking at UPS for studio at small station. A pure sign wave inverter unit is almost 4 times what a stepped or modified sine wave unit runs. Will the switch mode power supplies be OK with a modified or square AC wave? BTW using a kill-a-watt measurement I can keep a studio on air with only 380 watts max power consumption. Much less than I thought.
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UPS Systems Sine or not?
- Thread starter Fieldtech1
- Start date
A square wave UPS might cause some noise problems. Why not ask the manufacturers of your console and other studio equipment?
I've had good luck with APC brand UPS systems in every application - no issues about the waveform. That's the only brand I've used, however.
I wouldn't trust an estimate, or even measurement, of power consumption when there are switching power supplies involved. They all state consumption figures but those are average and switching power supplies have very short term peaks. If you're protecting one piece of equipment that's not a problem. But, protect several pieces, particularly computers, and it turns out there will be brief periods when actual draw is more than double that of the estimate or even the actual current/voltage measurement.
If there's a generator involved it gets even stranger and APC once told me to be sure generator capacity was at least two times what might seem adequate. Then you get into precision voltage and frequency control and it's complicated. I've found the support crew at APC (see their website) to be really helpful in keeping people out of trouble.
I wouldn't trust an estimate, or even measurement, of power consumption when there are switching power supplies involved. They all state consumption figures but those are average and switching power supplies have very short term peaks. If you're protecting one piece of equipment that's not a problem. But, protect several pieces, particularly computers, and it turns out there will be brief periods when actual draw is more than double that of the estimate or even the actual current/voltage measurement.
If there's a generator involved it gets even stranger and APC once told me to be sure generator capacity was at least two times what might seem adequate. Then you get into precision voltage and frequency control and it's complicated. I've found the support crew at APC (see their website) to be really helpful in keeping people out of trouble.
I once had a client with non-sinewave UPS units that didn't play well with a generator at all. The station found out the hard way after a utility failure and all the UPS units refusing to charge and a few refusing to stay on with generator power.
I must echo others as I've had very good support from APC, even on their long discontinued versions of their equipment.
I must echo others as I've had very good support from APC, even on their long discontinued versions of their equipment.
I use the APC smart UPS. Sometimes you need to go in with the Powerchute software and fine tune the setting to run once the generator has started. I would definitely use modified sine wave. And I have heard that the Kilo-watt meters don't play well with a UPS. I had a friend say it took out the meter and UPS when he plugged his into it.
Always test a ups system with the generator if you have one. If the UPS has a Voltage sensitivity select that can help matching your generator to the UPS. When sizing a generator its 60-80 percent of the load with the generator running best at 80% load.
What size UPS depends on load and run time. I usually get the smart ups models in the 1400Va range. And yes be careful of those ratings because they are usually in VA and not watts.
Always test a ups system with the generator if you have one. If the UPS has a Voltage sensitivity select that can help matching your generator to the UPS. When sizing a generator its 60-80 percent of the load with the generator running best at 80% load.
What size UPS depends on load and run time. I usually get the smart ups models in the 1400Va range. And yes be careful of those ratings because they are usually in VA and not watts.
D
DRoberts
Guest
Quit worrying about sine wave and all that other crap. Get you a quality Emerson "Liebert" UPS and be done with it. Be sure you get an online system instead of one of the APC pieces of crap. An online unit cleans and conditions the power constantly. It doesn't have to start up when the power fails. Just remember, no inductive type loads and make sure the UPS is never running over 70% loaded. UPS batteries last about 5 years so be ready to replace the battery packs at about that point. Keep it simple and it works better.
Chuck said:
I haven't used Cyber Power but it's nice to hear you have a happy system.
Repeating something I posted years ago....
At one point I had a 15 kVA diesel that was plenty for the station. Then, after a couple of years, I started having a "ping-pong" effect that took everything down. When city power failed everything that had a UPS went to the UPS until the generator fired up. Everything went back to the mains (now on generator power) as you'd expect. After a few minutes individual UPS units switched off the generator and back to battery. About half would get there before the trend reversed and they started to again accept the generator output.
It was APC's support folks who clued me in.
I put a scope on the building's AC then forced a city failure (popped the main breaker). Sure enough, loss of power then the generator came up with a reasonably decent waveform. But that didn't last long. Pretty soon voltage dropped and the waveform got really nasty. As UPS units went back to battery the voltage came up and the waveform cleaned up. Then the cycle repeated.
The culprit was......
COMPUTERS! Over the years the station went from having one computer to having over 30. A lot of older, power-hungry stuff was retired so the average load was about the same as when the UPS and the generator loved each other. The switching supplies in computers (and lots of other stuff these days) have a moderate AVERAGE draw but at any given moment the real draw may be double, even triple. Get enough of them bunching up and the load on the generator is much higher than the average you might calculate or measure. The heavy load messes up the generator.
The APC folks advised measuring the load with everything in the building turned on (Amprobe on each AC leg works nicely). Then TRIPLE that number to figure out the size generator you need. I measured full average load at just over 12 kW so there was no headroom in the 15 kVA diesel. Closest size to what I figured I needed was 36 kVA but, on a whim, I priced the next size up and found there was only a $200 difference between the 36 and the 55 kVA model I bought. That left plenty of headroom and a good thing as we're shortly adding to the building with four more studios. Then we'll retire the equipment in some earlier studios and eliminate a couple of makeshift editing spaces so the headroom won't go away.
APC also suggested spending the extra money for three options: Permanent magnet excitation. Precision voltage control. Precision frequency control. It added on another $1,500 or so; money well spent. That generator has been in service for 17 years now. The only failure was about 3 years after I retired and everybody left totally forgot about the fact that batteries don't live forever.
The APC systems mostly have the ability to set a range of acceptable voltage and some have settings for other parameters. Older ones use DIP switches; newer have USB capability. I make them pretty tolerant because if you don't make them MORE tolerant than any automatic transfer switch in the system you'll risk having them go over to battery after rejecting city power that the transfer switch finds perfectly acceptable.
All that said, a complete UPS backup (like they put in hospitals) would be really nice. But only if somebody's going to take proper care of the massive battery bank that goes with them.
No generator at studio, station owners are just tired of waiting 5 minutes for all systems to come back up from the power blinking for a second during a thunderstorm. STL and EAS unit in rack/telco room are on a UPS already.
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