Uninterruptible Power Supply Guide

An uninterruptible power source (UPS for short) or uninterruptible power supply is a type of electrical apparatus that provides a load with emergency power whenever the mains power or input power source fails. It is in contrast to a standby generator or emergency or auxiliary power system, in that it provides nearly instantaneous protection against input power interruption, through supplying energy that is stored in flywheels, supercapacitors, or batteries. A majority of uninterruptible power sources have fairly short (just a couple of minutes) of on-battery run-time. However, it is enough to get a standby power source started or to shut down protected equipment properly. It is a kind of continuous power system.

Typically a UPS is used for protecting hardware like telecommunication equipment, data centres, computers, and other types of electrical equipment where unexpected power disruptions can potentially cause data loss, serious business disruption, fatalities, or injuries. UPS units vary in size from units that are designed for protecting one computer with no video monitor (approximately 200 volt-ampere rating) up to large units that power entire buildings or data centres. The main role that any UPS plays is providing short-term power whenever the input power source has failed. The Riello UPS battery replacement is one of the popular choices of UPS.

Technology Behind UPS Systems

Modern UPS systems fall into three general categories, which are standby, line-interactive, and online. A “double conversion” method is used by an on-line UPS for accepting AC input, which rectifies to DC to pass through a rechargeable battery (or through battery strings), and then inverts back to 120V/230V AC to power protected equipment. The inverted is maintained in line by a line-interactive UPS and it then redirects the DC current path of the battery from the regular charging mode to supply current whenever power is lost. With an “off-line” or standby system the load is directly powered by the input power. Any backup power circuitry is invoked only when there is a failure of the utility power. A majority of 1 kVA are either standby or line-interactive and less expensive usually.

Dynamic Uninterruptible Power Supplies (DUPS) sometimes are used with large power units. A synchronous alternator/motor is connected via a choke on the main. Energy gets store inside of a flywheel. When there is a failure of the power mains, power on a load is maintained by an eddy-current as long as the energy of the flywheel is not exhausted. Sometimes DUPS are integrated or combined with a diesel generator which following a brief delay is turned on, to form a DRUPS (diesel rotary uninterruptible power supply (DRUPS).

In recent years a fuel cell UPS was developed that uses a fuel cell and hydrogen as a power source, to potentially provide long run times with small spaces.

Uses of UPS Systems


In a larger business environment where it is of great importance to have reliability, one large UPS also can be a single failure point that may disrupt numerous other systems. In order to provide greater reliability, numerous smaller UPS batteries and modules may be integrated together in order to furnish redundant power protection which is the equivalent of a single large UPS. “N+1” refers to when N modules can supply the load, that there will be N+1 modules contained in the installation. In that way, if one module fails, it won’t impact the operation of the system.

Multiple Redundancy

Numerous computer services provide a redundant power supply option, so in case one power supply fails, there are one or multiple power supplies that can power the load. That is a critical point – with each supply being able to power the whole server on its own.

Redundant protection may be extended even further by connecting each of the power supplies to its own UPS. That provides double protection from a UPS failure as well as a power supply failure, to ensure continued operation.

Outdoor Usage

Whenever a UPS system is installed outdoors, there are some specific features that it should have in order to guarantee that it will be able to tolerate weather without performance being affected. The manufacturer needs to consider factors like snow, rain, humidity, temperature and others when an outdoor UPS system is being designed.

Outdoor UPS systems may either be host mounted, ground (pedestal), or pole. Some outdoor environments may involve extreme cold, which in those situations the outdoor UPS system needs to have a battery heater mat included, or in extreme heat, the outdoor UPS system should have an air conditioning system or fan system.