UPS for PC: the importance of uninterruptible power supply for a computer, criteria for choosing a UPS unit

The quality of electrical energy in networks is always unpredictable. Lightning strikes, accidents at transformer substations, and peak loads can all cause voltage surges strong enough to damage sensitive electronics. Even minor network problems can lead to computer shutdowns and loss of important information. The task of uninterruptible power supplies is to protect equipment from such risks.

Problems in electrical networks

Losses in the quality of supplied electricity are not necessarily due to natural disasters and accidents. The stability of the voltage and its parameters depends not only on the state of the networks, but also on the energy consumers. This is especially true for industrial areas where a large number of powerful equipment is concentrated, the operation of which can significantly affect the quality of electricity in the network. Daily power surges, frequency and amplitude distortions can be detrimental to computers and software. The main problems in electrical networks:

• Sudden power surges. Can only last a few milliseconds. The most common causes are power line accidents and lightning strikes during a thunderstorm.
• Disconnections. Usually associated with network overloads, accidents and repairs.
• Short voltage rises. Occur during shutdown of large loads such as commercial air conditioners and industrial engines.
• Long voltage drops. Connected with the connection of large electrical loads. May be seasonal, such as caused by the use of residential air conditioners during the summer months.
• Energy pollution. A consequence of electromagnetic and radio frequency interference caused by the operation of equipment such as welding machines, fluorescent lamps, high-power switches. Such devices are capable of distorting the AC sine wave.

The importance of protection

Despite the constant work of manufacturers on the reliability of their technology, computers have been and remain complex and demanding devices for the quality of power supply. An unexpected network failure can result in an abnormal shutdown without saving current data. Even if it is possible to recover the lost information, such an accident will entail a loss of time, energy and can be expensive.

Power outages are not only problems with maintaining current data, but also risks of damage to hardware or software. There are a number of situations where a power interruption can lead to irreversible consequences. An example would be the process of writing to a hard disk. A power failure during defragmentation or formatting can lead not only to the loss of processed information, but also to physical damage to the drive with the loss of everything that was stored on it.

The hard drive isn't the only power-sensitive component. The entire computer is saturated with oscillatory circuits connected to each other.

Although such events are statistically unlikely, during power outages there are always risks of induction of currents by the coils that could damage the computer.

The worst nutritional hazards do not appear immediately. Such threats to the operation of electronics include prolonged overvoltage or undervoltage (less than 207 V and more than 253 V). Computers operating in such conditions have a dramatically reduced resource, primarily from overheating, since their components are designed for a different operating voltage.

UPS device and types

An uninterruptible power supply unit for a computer, or UPS (acronym for the English Uninterruptible Power Supply), is designed to automatically ensuring emergency power supply without delays or transients in the event of voltage interruptions or impermissible quality electricity in the network. These devices are also capable of filtering or regulating power before it reaches the load.

An uninterruptible power supply for PC is not intended to ensure the operation of a computer for a long time, its task is to support operation of the device for a period of time sufficient to save data and correct termination work. Basically UPS (Uninterruptible Power Supplies) consist of following components:

• Rectifier. Its function is to convert AC to DC, which will be used to charge the battery and fed to the inverter.
• Battery. Used to store backup energy in the event of a main power failure.
• Inverter. Does the opposite of the rectifier: converts the incoming DC to AC for use by the load. The output of the inverter is a sinusoid with constant frequency and amplitude.
• Contactor. An automatic switch or transformer relay is needed to change the circuit when changing the voltage source. This component requires a very short response time, typically switches with a lag of about 10 milliseconds are used.

The easiest and most common way to solve most power quality problems is to connect your computer through a voltage relay or protection device.

These inexpensive devices are able to automatically correct for changes in input voltage and serve as a noise and distortion filter. Unlike these devices, the UPS relies on a battery for many tasks. In much the same way, a laptop battery serves as a surge protector and an alternative source of energy at the same time. The main types of UPS:

• Reserve type. These are the simplest and most inexpensive systems, providing only basic protection. In normal mode, they transfer power from the mains directly to the load and maintain battery charging. If the UPS automation detects undervoltage, it turns on the inverter to keep the equipment running on battery power. These devices are relatively slow, the delay between the loss of the mains and the start of the inverter can be long enough to disrupt the operation of sensitive loads. This UPS design usually does not provide complete surge protection, but works effectively as an electrical noise filter.
• Interactive type. They are similar to standby, but use a transformer for stepwise voltage stabilization. Provides faster transfer to backup power than the simplest UPS type.
• Double conversion. Designed to provide instantaneous transfer to standby power. In this type of UPS, the inverter is turned on constantly, and the load is powered only from it. This type of UPS got its name due to the fact that for operation it converts alternating current into direct current in the battery charging circuit and, conversely, at the output for connecting the load. Such systems usually provide complete protection of the power supply from any surges, but, as a rule, they consume a lot of energy for their work, are prone to heating and are not cheap.

Features of choice

It will not be difficult to choose a UPS for a computer if you know the basic parameters by which these devices differ from each other in purpose. The first and main criterion to be determined is the planned power consumption of the connected devices. If the latter need more energy than the UPS is capable of generating, they will not be able to turn on even if the UPS battery is fully charged.

The next parameter influencing the selection is the duration of the emergency operation. Often, an uninterruptible power supply is sufficient, capable of generating voltage for several minutes after shutdown. This is the time it takes to shut down the computer properly and save the information. If devices are required that can generate voltage for a long time after disconnection, it should be borne in mind that they are much more expensive.

Most UPSs come with features such as battery notification, software suite and USB connectivity for fine tuning. The most complex of them are equipped with a full indication of the battery charge and the predicted battery life, as well as the possibility of "hot" battery replacement. Most consumers do not need these options, but knowledge about them and familiarity with the features of each model can be important for choosing.

Uninterrupted devices serve as long as the built-in battery retains its properties. As a rule, this period does not exceed two to three years. This is because batteries age faster when operated under full charge conditions. Therefore, the warranty period for the UPS does not exceed three years, with rare exceptions.

The reliability of the backup battery is an important criterion when choosing a UPS.

Most of the dangers that a modern UPS can protect against are unlikely. But if expensive equipment is connected to the network or its malfunction can lead to serious consequences, the purchase of a UPS will not be a superfluous investment. In this case, the very first serious power surge pays for the cost of protection.