Uninterruptible Power Supply

What's a power outage?

Uninterruptible Power Supplies

An uninterruptible power supply or uninterruptible power source (UPS) is an electrical apparatus that provides emergency power to a load when the input power source or 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, supercapacitors, or flywheels. The on-battery run-time 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. It is a type of continual power system.

Power Management Types

UPS devices are available in 3 major categories according to the way they manage a power failure:

Offline / Standby

The offline/standby UPS (SPS) offers only the most basic features, providing surge protection and battery backup. The protected equipment is normally connected directly to incoming utility power. When the incoming voltage falls below or rises above a predetermined level the SPS turns on its internal DC-AC inverter circuitry, which is powered from an internal storage battery. The UPS then mechanically switches the connected equipment on to its DC-AC inverter output. The switchover time can be as long as 25 milliseconds depending on the amount of time it takes the standby UPS to detect the lost utility voltage. The UPS will be designed to power certain equipment, such as a personal computer, without any objectionable dip or brownout to that device.

Line Interactive

This type of UPS is able to tolerate continuous undervoltage brownouts and overvoltage surges without consuming the limited reserve battery power. It instead compensates by automatically selecting different power taps on the autotransformer. Depending on the design, changing the autotransformer tap can cause a very brief output power disruption, which may cause UPSs equipped with a power-loss alarm to “chirp” for a moment.

This is the most common type of SOHO UPS type as the batteries need less maintenance, although the autotransformer is prone to failure.

Online / Double-Conversion

In an online UPS, the batteries are always connected to the inverter, so that no power transfer switches are necessary. When power loss occurs, the rectifier simply drops out of the circuit and the batteries keep the power steady and unchanged. When power is restored, the rectifier resumes carrying most of the load and begins charging the batteries, though the charging current may be limited to prevent the high-power rectifier from overheating the batteries and boiling off the electrolyte. The main advantage of an on-line UPS is its ability to provide an “electrical firewall” between the incoming utility power and sensitive electronic equipment.

This is ideal for industrial, data center, and large business use where there are multiple high voltage lines running through the same circuit, as this type of UPS provides electrical isolation to your valuable equipment.

How to calculate VA

VA stands for VoltAmperes, which is calculated exactly as it sounds Volts * Amps. It represents the Apparent Power the UPS unit can provide. The calculation formula via wattage  is Watts / Power Factor. The Power Factor is about 0,7 (depends on the power grid), which means a good measure would be 75% * VA to get the watts the UPS unit can manage.

Battery time

UPS units contain one or more, usually 12V, batteries. The capacity and number of batteries play a major role in the running time of your equipment (on battery power). Most SOHO UPS units have a battery time of a few minutes, 5-20 depending on the load. It is a good practise to buy larger (in VA) UPS than required to get more battery time out of it but there are also units that offer more running time with the same VA due to having larger/more batteries.

SOHO Solutions

Spinworks provides a wide variety of UPS solutions for small offices and home use, varying from 450VA to 2500VA depending on your needs. Most UPS products of this range provide direct schuko connectors for convenience while many also provide phone line surge protection and USB connection for PC monitoring.

Business Solutions

Business line UPS products range from 1000VA to 20000VA and come in all shapes and sizes, even rack-mountable! They incorporate many business features such as network administration, automation actions, third party management protocols to integrate with your existing power grid management software and more.

enterprise Solutions

Custom UPS solutions with battery arrays and enterprise inverters, even 3-phase 380V AC or custom DC-DC solutions, are also available for more demanding situations. The main advantage here is the scalability. You can start small, say at 10000VA and later expand tenfold or more. This is an ideal setup for growing organizations who take their power seriously!

Information source: Wikipedia