Uninterruptible power supply (UPS): what it is, types, how to choose

Uninterruptible power supply (UPS) is equipment that supplies power to equipment after a power outage for some time. Computers, medical equipment and household appliances are connected to it. The device has a rechargeable battery that instantly supplies power if the power goes out. Usually, the UPS beeps, sends a notification to your smartphone, or notifies you in some other way. A battery charge can last up to 24 hours, depending on power and load. During this time, you can restore power, save data, or shut down equipment. If the voltage fluctuates, the UPS intercepts it and supplies the equipment with a stable current.

Types of uninterruptible power supplies

UPS are of these types:

• UPS passive standby UPS works offline. This is a simple uninterruptible power supply, designed for low-power household and office equipment. The battery charge lasts for a maximum of 30 minutes.
• Line-interactive UPS are used in corporate IT networks, banks and engineering systems. They are not suitable for all types of equipment. Heating boilers, laboratory medical equipment are very sensitive to voltage quality. Line-interactive UPSs give output voltage distortions.
• Dual-conversion UPSs work online. Such devices provide uninterrupted power during any malfunctions in the power grid and give the most accurate and stable voltage.

Uninterruptible power supplies vary in power:

• UPS power not more than 3 kilo-volt-amperes (kVA) - these are devices with one phase. To these devices are connected refrigerators, boilers, pumps, automatic gate drives, etc.
• UPS with a capacity not exceeding 20 kVA are single-phase and three-phase equipment. They provide centralized power protection for an entire apartment or small office.
• UPS above 20 kVA and up to 500 kVA are three-phase equipment for stabilizing the power supply of industrial facilities.

The design of uninterruptible power supplies differs:

• Wall-mounted device of small power is mounted near the equipment that will be connected to it.
• Floor UPS or tower are installed on the floor, racks, they create complexes of UPS.
• Rack or rack units are mounted on shelves or in 19-inch rack cabinets.
• Combined tower/rack units are mounted vertically or horizontally, on the floor or in cabinets.

How to choose an uninterruptible power supply

The output power of the UPS must be the same as the power consumption of the equipment. If an uninterruptible power supply will be used for several household devices or office equipment, consider their total power consumption. Some devices consume more power during power on than in normal mode. The UPS is selected by output power, taking into account the peak load.

If the equipment to be connected to the device is very sensitive to the slightest power delay, a UPS with double current conversion is needed. The interactive UPS have a 4-6 ms delay, the stand-by UPS have a 6-10 ms delay.

UPS come with built-in or external batteries. If the battery is outside, it is easier to repair or replace. There are uninterruptible power supplies with removable batteries.