Fortunately nowadays, uninterruptible power supplies were born, providing the necessary first line of protection and power for our units, especially during brownouts and power surge. [You may want to see: Uninterruptible Power Supply: Perfect device to save your business!]
UPS is like a battery backup. When the main power source if fine, it simply acts as a power surge or spike protection, in some model, it has the feature of voltage regulation. When the main supply fails, UPS comes to the rescue. What it does is that it switches over the backup power supply, usually the batteries and turns the 12 or 24VDC battery voltage into a 220VAC mains voltage to feed your device.
Things to consider in buying
Inverters and batteries
The capacity of the inverter to power a load and the capacity of the batteries to keep it running is a must know for every unit. The inverter delivers a certain maximum power output.
Power capacity is usually measured in volts-amps (VA) or watts (W) – VA is the AC apparent power rating and watts is the DC or actual power used rating. Look for the watts rating on consumer grade UPS. Not all units publish this up-front since it’s the smaller number, in this case, take 60% of the VA figure as the fair approximate of the watts rating, the real load the unit can handle.
For batteries, the bigger the battery, or the more battery it has, the longer the inverter keeps running. But it is not just that simple. Why?
- SLA batteries are quite heavy that if you add in two batteries, the UPS is of 10 kilos of weight
- The battery has to have sufficient capacity to handle the demand of the inverter
- Bigger battery capacities last proportionally longer than smaller ones
How to choose?
UPS watt rating must match the power draw of the device you want to power. How long a UPS runs depends on whatever you just want to properly shutdown or to keep your device running. This sets the size, capacity and price of the UPS you need to choose.
Know the specs and terminologies
AVR is an abbreviation for Automatic Voltage Regulation. It is designed to improve the quality of the AC voltage form the wall socket. Raising this voltage to the right level during brownouts and dropping it during surges is the process of voltage regulation. All UPS have AVR when running on battery.
2. Modified or simulated sine wave output
AC mains supply voltage alternates in the form of 50/60 hertz sine wave. Making the AC inverter do these is expensive, that other brands use a modified r simulated sine wave that a series of rising and falling voltage steps.
3. Power Factor
Power Factor (PF) is the ratio between this real watts power used to the apparent VA power required. A simple incandescent lamp is purely resistive that it has a PF of 1.0. An induction motor may have a PF 0.5 where half of the power disappears back into the electricity grid but still has to be supplied for the motor to run. This is why inductive loads are always more difficult for UPS or inverters to power because they need access to more power than they actually use.
Having the right knowledge about UPS basic operations, inverters, batteries, AVR, VA, Watts and PF will help you decide what is the right UPS that will suites your needs. If I missed one out, please feel free to drop it at the comment box below. It would be nice to hear from you.
You have questions? Browse here: Uninterruptible Power Supply Q&As
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