Given the same vendor claims, how can I tell a "good" quality UPS from a "poor" quality UPS?
Testing, testing, testing. I can't emphasize this enough. There are many good and bad units out there that call themselves UPS's. There are many good units that are not suitable for your need.
Some properties you might look for, include:
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Sinusoidal power output. In general, the closer the AC output of the UPS is to a sine wave, the better it is for your equipment. Many UPS units, especially the cheaper ones, deviate a great deal from a sinusoidal output. Some of them generate square waves. Waveform effects are dealt with in next question of this document.
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Does the UPS have a manual bypass switch? If the UPS is broken or is being serviced, can you pass power through it to your equipment? The last thing you want is for a broken UPS to be the cause of extra downtime.
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The more information about a UPS operation you can get from watching the unit itself, the better. How much power (or percentage load) the equipment is drawing, how much battery life is left and indications of the input power quality are all very useful.
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Some newer UPS's can communicate with their monitoring software via a network connection and SNMP. This is wonderful if your network is on a UPS. Also, beware, I have heard of dealers advertising "Network UPS" monitoring where the network is the normal serial connection.
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Does the UPS vendor offer support/maintenance contracts? If they aren't offered, I would suspect the quality of the equipment.
If you do have a UPS that does not have a sinusoidal waveform, some manufacturers strongly urge you not to put a surge protector between the UPS and the computer. The surge protector might mistake the non-sine waveform as a power surge and try to send it to ground. This could be bad for your UPS, not to mention your equipment. I don't know if this has happened or not, but I wouldn't chance it.
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What does "line interactive" mean?
What we call "true on-line" UPS systems, are those supplies that continuously operate from an inverter. Obviously, there is no switchover time, and these supplies generally provide the best isolation from power line problems. The disadvantages to these devices are increased cost, increased power consumption and increased heat generation. Despite the fact that the inverter in a "true on-line" UPS is always on, the reliability of such units does not seem to be affected. In fact, we have seen more failures in cheaper line interactive units. [ Note: that given the same quality inverter, you'd expect the one that runs least lasts longest.]
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What equipment and appliances can I use UPS for?
You can plug almost any equipment into your UPS. Some examples include lamps, portable phone stands, computers, televisions, stereos, fax machines, cash registers, and phone systems. Do remember that a small UPS products cannot start motors or run large appliances like sump pumps, furnaces, air conditioners, refrigerators, elevators and other major appliances because they require more power than a UPS battery can provide.
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My business is too small for protective measures. Do I really need a UPS?
Power problems are not restricted to larger organisations. Your PCs, servers and network are just as critical to your business as a data centre is to a large enterprise. Downtime is costly in terms of hardware and potential loss of goodwill, reputation and sales. You must also consider the inevitable delays that occur when rebooting locked-up equipment, restoring damaged files and re-running processes that were interrupted. A sound power protection strategy provides cost-effective insurance.
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How do you convert amps to VA?
Multiply amps by voltage. 10A x 230V = 2300 VA
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How do you convert watts to VA?
Divide watts by the power factor, for example 1000W/0,7 p.f=1429 VA17.
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What’s the difference between VA and watts?
In order to correctly size a UPS, it is important to understand the relationship between watts and VA. However, we must first think about power terminology. Real power (measured in watts) is the proportion of power flow that results in the consumption of energy. The energy consumed is related to the resistance in an electrical circuit. An example of consumed energy is the filament in a light bulb. Reactive power (measured in VAR or volt-amps reactive) is the proportion of power flow resulting from stored energy. Stored energy is related to the presence of inductance and/or capacitance in an electrical circuit. An example of stored energy is a charged flash bulb in a camera. Apparent power (measured in VA or volt-amps) is a mathematical combination of real power and reactive power. The geometric relationship between apparent power, reactive power and real power is illustrated in the power triangle below:
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How much UPS capacity do I need?
Determine the total load (in watts) of the equipment you want to protect. Add 10-20 per cent to allow for future growth and decide the minimum amount of runtime you need. Use the online sizer at www.eaton.com/powerquality to identify the right solution for your application.
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How long can equipment on a UPS keep running after the power goes?
That depends on how big a UPS you have and what kind of equipment it protects. For most typical computer workstations, one might have a UPS that was rated to keep the machine alive through a 15 minute power loss. If it is important for a machine to survive hours without power, one should probably look at a more robust power backup solution that includes a generator and other components. Even if a UPS powers a very small load, it must still operate its DC (battery) to AC converter (the inverter), which costs power. A rough extrapolation from EATON's documentation, leads me to guess that its 2200 VA UPS can operate its own inverter (with no extra load) for just over 8 hours. A 1200 VA UPS could run its converter for about 5 hours.
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A power surge is a sharp increase in voltage. Surges can occur on your electric, phone or even cable TV lines. They are often caused by lightning but can be associated with many other types of uncontrollable events such as hurricanes, tornadoes, ice storms, vehicle accidents involving utility equipment, etc. The most common type of surges are caused by the starting of motor-driven equipment such as your refrigerator, air-conditioner, furnace or garbage disposal.
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