# UPS - Uninterruptible Power Supply



## NaeKid (Oct 17, 2008)

What is a UPS? Is it the shipping company - well, ya. But, seeing as this is the energy and electricity section, a UPS has a whole different meaning.

http://en.wikipedia.org/wiki/Uninterruptable_power_supply

*An uninterruptible power supply, also uninterruptible power source, UPS or battery/flywheel backup, is an electrical apparatus that provides emergency power to a load when the input power source, typically mains power, fails. A UPS differs from an auxiliary or emergency power system or standby generator in that it will provide near-instantaneous protection from input power interruptions, by supplying energy stored in batteries or a flywheel. The on-battery runtime of most uninterruptible power sources is relatively short (only a few minutes) but sufficient to start a standby power source or properly shut down the protected equipment.

A UPS is typically used to protect computers, data centers, telecommunication equipment or other electrical equipment where an unexpected power disruption could cause injuries, fatalities, serious business disruption or data loss. UPS units range in size from units designed to protect a single computer without a video monitor (around 200 VA rating) to large units powering entire data centers or buildings. The world's largest UPS, the 46-megawatt, Battery Electric Storage System (BESS), in Fairbanks, AK, powers the entire city and nearby rural communities during outages.*

Alright, now that the basic information about the UPS is covered, there are ways to extend the "life" of the UPS so that it can keep your equipment protected and running for extended periods of time. Watching the following video will give you the basics for a few more hours of AC-power out of a cheap UPS.






There is another way to extend the usable life of a UPS and that is to combine it with a secondary charging system, like a solar-panel or wind-generator (or both). The UPS will have a power-rating in VA that it can power. A UPS that has a 650 number on it has half the power capablity as one with a 1200 number on it. At home, I have some with a 180, some with a 350, some with a 650 and a few upto 2200. My little 180 rated UPS will run equipment like my cordless-phone base, my internet-modem and wireless router for hours. My big 2200 UPS will run equipment like my deep-freeze or my furnace fan.

There are even bigger UPS systems that are capable of running an entire house with 10,000watt of capablity. Those systems need to be wired directly into the house-wiring and are not easily portable.

A UPS is best used to keep equipment running until you have a chance to power it down safely or to switch over to a more robust system. In the case of the whole-house UPS, the batteries can be connected to a solar-panel for charging and you can add more batteries as required anytime that you feel the need to add more batteries. The whole-house UPS can be used to power your garage, fridge, freezer, AC, furnace and all kinds of other stuff.

APC (American Power Corporation) is the biggest UPS manufacturer with many small Chinese companies starting to flood the market with their equipment. DCACPower (http://www.dcacpower.com/) makes some great whole-house UPS systems with 12,000 peak watt units (6,000 continous watt running). There are many other companies that also make great equipment for emergency power systems.

Personally, I would use the UPS as a backup power system and have several of them. Have a dedicated UPS to each major system in the house. It costs more, but, you can tailor your systems to your requirements. To get started, a $50 UPS will power your small electronics, a $100 UPS will power your computer or your home stereo, a $150 UPS can keep your garage-door opener functioning, a $200 UPS will run your fridge and another one will run your freezer and another one will run your furnace-fan (you will still need natural-gas for the heat) or you could just wire a $500 UPS (plus-batteries) into the house wiring for critical-systems (furnace, fridge, freezer).


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## Tex (Oct 31, 2008)

Any RE power that uses batteries and inverters is a modular UPS. I suspect that you would pay a premium for individual UPS all over your house. Keeping up with maintenance would be a hassle also. A 10-15kva UPS would handle an entire house. Most of these have a DC bus at over 200VDC. That requires more batteries in series. It's not dangerous if you know what you are doing, but make sure you know what you are doing. You'll have to keep the equipment locked away from curious children.

There are several inverters built for the home power market. Most run at 24 or 48VDC and would be much safer and practical for the home market. If you have a UPS with a 240VDC bus, you would need 20 12V solar panels to feed it directly and they would have to be wired in series.

I recommend a small UPS for critical circuits. (computer, sattelite, stereos, TV, home automation, security) The rest of the house can take the outage and wait for generator. If you have a whole house inverter, then you're good anyway. 

On a small scale, I have done exactly what the guy in the video did for my computer. I'm always finding little APC units that customers will give away after I fix their big UPS. I now only use a laptop and a UPS would be redundant.


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## LincTex (Apr 1, 2011)

Tex said:


> On a small scale, I have done exactly what the guy in the video did for my computer. I'm always finding little APC units


Me too, people throw them away all the time... I have a whole bunch of the small ones and a few 1000/1200 Va units.



NaeKid said:


> My big 2200 UPS will run equipment like my deep-freeze or my furnace fan.


Ok., I have to be the "devil's advocate".... Have you actually tried to run any induction motors from your UPS? From what I understand, "common" UPS output power is pretty much always modified sine wave. Induction motors hate it.

Try to use some old appliances for the test... I would hate for your nice units to be ruined. I have one old small "dorm/apartment" fridge I need to try out.


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## LincTex (Apr 1, 2011)

Ok, so I did a little searching....

Interestingly enough, when i started to type in the google search box, it did an auto-complete for me with this exact phrase: "modified sine wave + induction motors" so I clicked on it to fill in....

Here is an interesting explanation:
http://www.nooutage.com/inverter1.htm

Most low-cost inverters have modified square wave output (sometimes called modified sine wave) with harmonic distortion of around 40%. They are an economical choice in power systems where waveform is not critical. Their high surge capacity allows them to start large motors while their high efficiency makes them economical when running small loads like a stereo or a small light. They can power most lighting, televisions, appliances and computers very well. We do not recommend them for computer systems with laser printers. Unfortunately, this type of inverter may destroy some low cost rechargeable tools and flashlights, and their waveform will not allow many laser printers, copiers, light dimmers and some variable speed tools to operate. Some audio equipment will have a background buzz that may be annoying to music connoisseurs. Due to the wave form and high harmonic distortion some motors will consume more power on a modified square wave. The result is more noise, heat and losses. This is not usually a problem if this type of wave form is only being used for brief and infrequent backup power. However, for continuous year-around use, a _motor running hotter will have a shortened expected life_. You may even hear a distinct hum when running on modified sine wave power.


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## NaeKid (Oct 17, 2008)

Thanks for sharing that. I will take a closer look at my system and see if there is something that I am missing. 

I remember years ago a customer purchased a brand new HP LaserJet 5000 with all the goodies to the tune of about $10,000. I was sent out there via private-plane to install and test the new printer. Due to power problems in their office-location (field-office for a lumber company in the back-woods of BritishColumbia) I tested and installed a $5000 UPS with that unit. It worked well enough that the printer no longer gave out continous errors. It also allowed the printer to keep running safely for about 10 minutes (while printing / sorting) if there was a brown-out in progress, which was common out there.

I can't remember which UPS it was that I ordered for them from the APC website, but, it was the only one recommended for the power requirements of that laser-printer.


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## labotomi (Feb 14, 2010)

LincTex said:


> Ok., I have to be the "devil's advocate".... Have you actually tried to run any induction motors from your UPS? From what I understand, "common" UPS output power is pretty much always modified sine wave. Induction motors hate it.
> 
> Try to use some old appliances for the test... I would hate for your nice units to be ruined. I have one old small "dorm/apartment" fridge I need to try out.


I'll say that we use pulse width modulated inverters for variable frequency control on hundreds of motors at my facility. They are all induction motors. some are inverter duty rated and some aren't, it mostly depends upon the distance between the motor and the drive unit.

They're made to work with motors, not because of special signal output, but other ancillary features. Try holding a 300Ton crane load stationary without using a brake. These drives can give full torque with zero motion. Try that with an across the line motor and you get locked motor current. Hopefully the breaker will trip before the motor burns up.

The drives themselves aren't so different than a normal household inverter other than they have more capabilities. The actual waveform going to the motor is the same


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## LincTex (Apr 1, 2011)

labotomi said:


> Try holding a 300 Ton crane load stationary without using a brake. These drives can give full torque with zero motion. Try that with an across the line motor and you get locked motor current.


I have never heard of such a critter. That is VERY impressive.


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## NaeKid (Oct 17, 2008)

Dayumn... 300 ton ... and I thought my 75-ton overhead-cranes here at work were kickass. I get woody just thinkin' about that kinda power :congrat:


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## Dixie (Sep 20, 2010)

gee, I wish I knew what y'all were talking about.


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## Padre (Oct 7, 2011)

I've got two of them...


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## labotomi (Feb 14, 2010)

LincTex said:


> I have never heard of such a critter. That is VERY impressive.


It's termed AC Vector control. I'm not sure who came up with it, but all the major manufacturers have been using it for a while... Siemens, Allen Bradley, Reliance, Omron, Electromotive and others. Some are just rebranded versions of the above.

Ours are holding liquid metal, so I'm sure they're over designed.

The ladles weigh about 100T and they each hold 170T of molten steel. The holding brakes drums actually get rust pitting because the only time the brake engages is after the load comes to a complete stop and it releases after the motor is holding the load, but before motion occurs. Quite a bit different than the eddy current brakes used in an older facility I worked a while ago.

I don't fully understand all the factors that have to be accounted for, but I know that every time we change a motor, it has to be tuned uncoupled from the shaft so that the drive can know exactly what to expect from the motor concerning resistance, reactance, slip, magnetization current etc.

You can look up AC vector control, but realize that all the discussions I've seen get complicated quickly.


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## Fn/Form (Nov 6, 2008)

I used to sell/service UPS products ranging from 250VA to 1.1MVA. From computer size to 11 story data center size. The small APC systems had palm-sized batteries. The largest systems featured individual battery cells that were as big as a dishwasher. About 800 of those cells in each battery plant.

The most common home/small business types are *true online* models and *line interactive* models. A true online or "double conversion" UPS changes incoming power (AC) to battery power (DC) and then changes it back to AC. The true online usually features a quality sinewave output with low distortion. This is important for some equipment. The true online models are more expensive and consume more power.

The "line interactive" models are cheaper, and 95% of home models are this type. It is not truly online, but rather simply charges the battery until backup power is needed. It senses when there are power problems and then almost instantaneously starts the backup power. They are generally very good about keeping the backup power in phase with the failed power. They work great with laptops where the battery covers any lapses during the transition to backup power. But sometimes the tiny switch-over time causes problems for sensitive equipment. They use less power than a true online, but they also have shorter run time.

Some people extend the cheaper line-interactive model run time by adding larger batteries on the outside of the unit. This usually works OK, but the line-interactive models aren't designed with long runtimes in mind. They don't have cooling fans or great convection designs. They can overheat or go into thermal shutdown before the batteries are exhausted. A very small fan can help tremendously with longer runtime reliability. Also, since their battery chargers are intended for small batteries, they have a long recharge time for large batteries.

The worst enemy of ANY sealed lead acid (SLA)/gel cell/absorbed glass mat (AGM) battery is HEAT. They're designed and spec'd at telecom room or summer air conditioning temps. Raising the temp 10-15 degrees can cut battery life IN HALF. Remember my mention of poor thermal design on the line interactive models? The battery is typically butted up next to the charger/inverter heatsink in the line-interactive UPS. This is great space-saving under your desk or on top of you desk. But it is not good for long battery life.


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