What’s an Uninterruptible Power Supply?

An uninterruptible power supply (UPS) is an electrical apparatus used to provide emergency power to a load in case of failure of the mains power or input power source. A UPS differs from an emergency or auxiliary power system or standby generator since it offers almost-instantaneous protection from interruptions of input power, by supplying energy stored in flywheels, supercapacitors, or batteries. UPS systems typically have a relatively short (just a few minutes) on-battery run-time, but this is usually sufficient to properly shut down the protected equipment or start a standby power source.

A UPS is typically used for protecting hardware such as telecommunication equipment, data centres, computers, or other types of electrical equipment where an unexpected disruption in power could lead to fatalities, injuries, data loss, or serious business disruption. UPS systems typically range in size from devices designed to offer protection to just one computer without a video monitor (about 200 VA rating) to large units that power entire buildings or data centres. Getting hold of UPS is fairly simple from online shops like the UPS Battery Shop. The key role of a UPS is providing short-term power in case of failure of the input power source.


Modern UPS systems are of 3 general categories i.e. standby, line-interactive, and online. On-line UPS systems use a “double conversion” method of accepting AC input, rectifying to DC to pass through the rechargeable battery, then inverting back to 120V/230V to power the equipment that’s being protected. Line-interactive UPS systems maintain the inverter in line and redirect the DC current path of the battery from the normal charging mode to providing current in case the power is lost. In standby UPS systems, the load is powered directly by the input power and the backup power circuitry is used only in case of failure of the utility power. UPS systems below 1kVA are of the standby or line-interactive variety, which tend to be cheaper.

Dynamic Uninterruptible Power Supplies (DUPS) are used sometimes for large power units. A synchronous alternator/motor is connected on the mains through a choke. A flywheel is used to store energy. In case of failure of the main power, an eddy-current regulation helps maintain the power on the load as long as the energy of the flywheel has not been exhausted. DUPS are sometimes integrated or combined with diesel generators that are turned on after a brief delay this forming diesel rotary uninterruptible power supply (DRUPS).

In recent years, a fuel cell has been developed using hydrogen and a fuel cell as a source of power, potentially offering long run times in a small space.



A single massive UPS can be a point of failure with the potential to disrupt numerous other systems in large business environments where reliability is very important. To offer more reliability, multiple smaller UPS batteries and modules can be integrated together to offer redundant power protection that’s equivalent to a single massive UPS. “N+1” means that if N modules can supply the load, the installation will contain N+1 modules. In that way, if one module fails, the system’s operation won’t be affected.

Multiple Redundancies

Computer servers usually offer the option of redundant power supplies such that one or more other power supplies can power the load in case one power supply fails. This is one critical point – each power supply should have the ability to power the whole server by itself.

Connecting each power supply to its own UPS is another way to extend redundant protection further. This provides double protection in case of a failure of the UPS and power supply to ensure that operations are never interrupted.

Outdoor Use

If a UPS system is placed outdoors, it needs to have some specific features guaranteeing that it can tolerate all kinds of weather without any effects on performance. Manufacturers should consider factors such as rain, humidity, temperature, and snow among others when designing an outdoor UPS system.

Outdoor UPS systems can be ground, pole or host mounted. Outdoor environments could mean extremely low temperatures, in which case the outdoor UPS system needs to include a battery heater mat, or extremely high temperatures, in which the outdoor UPS system needs to include an air conditioning or fan system.