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An emergency power system is an independent source of electrical power that supports important electrical systems on loss of normal power supply. A standby power system may include a standby generator, batteries and other apparatus. Emergency power systems are installed to protect life and property from the consequences of loss of primary electric power supply. It is a type of continual power system.
They find uses in a wide variety of settings from homes to , scientific laboratories, , Fuel cell in the data center Munich telecommunication India orders 10.000 fuel cell emergency power systems equipment and ships. Emergency power systems can rely on Engine-generator, deep-cycle batteries, flywheel energy storage or . Fuel Cells in Backup Power Applications DOE Fuel Cells for Backup Power
Some larger building have , but they can take 5 or up to 30 minutes to produce power.[5] Gas Turbines In Simple Cycle & Combined Cycle Applications | Claire M. Soares
Lately, more use is being made of deep cycle batteries and other technologies such as flywheel energy storage or . These latter systems do not produce polluting gases, thereby allowing the placement to be done within the building. Also, as a second advantage, they do not require a separate shed to be built for fuel storage.
With regular generators, an automatic transfer switch is used to connect emergency power. One side is connected to both the normal power feed and the emergency power feed; and the other side is connected to the load designated as emergency. If no electricity comes in on the normal side, the transfer switch uses a solenoid to throw a triple pole, double throw switch. This switches the feed from normal to emergency power. The loss of normal power also triggers a battery operated starter system to start the generator, similar to using a car battery to start an engine. Once the transfer switch is switched and the generator starts, the building's emergency power comes back on (after going off when normal power was lost).
Unlike , emergency lighting is not a type of light fixture; it is a pattern of the building's normal lights that provides a path of lights to allow for safe exit, or lights up service areas such as mechanical rooms and electric rooms. , fire alarm systems (that are not on back up batteries) and the electric motor pumps for the are almost always on emergency power. Other equipment on emergency power may include smoke isolation dampers, smoke evacuation fans, elevators, handicap doors and outlets in service areas. Hospitals use emergency power outlets to power life support systems and monitoring equipment. Some buildings may even use emergency power as part of normal operations, such as a theater using it to power show equipment in accordance with the principle of "the show must go on".
In commercial and military aircraft it is critical to maintain power to essential systems during an emergency. This can be done via Ram air turbines or battery emergency power supplies which enables pilots to maintain radio contact and continue to navigate using MFD, GPS, VOR receiver or directional gyro during for more than an hour.
Localizer, glideslope, and other instrument landing aids (such as microwave transmitters) are both high power consumers and mission-critical, and cannot be reliably operated from a battery supply, even for short periods. Hence, when absolute reliability is required (such as when Category 3 operations are in force at the airport) it is usual to run the system from a diesel generator with automatic switchover to the mains supply should the generator fail. This avoids any interruption to transmission while a generator is brought up to operating speed.
This is opposed to the typical view of emergency power systems, where the backup generators are seen as secondary to the mains electrical supply.
To achieve more comprehensive loss protection, extra equipment such as , inverters, or sometimes a complete uninterruptible power supply (UPS) is used. UPS systems can be local (to one device or one power outlet) or may extend building-wide. A local UPS is a small box that fits under a desk or a telecom rack and powers a small number of devices. A building-wide UPS may take any of several different forms, depending on the application. It directly feeds a system of outlets designated as UPS feed and can power a large number of devices.
Since telephone exchanges use DC, the building's battery room is generally wired directly to the consuming equipment and floats continuously on the output of the rectifiers that normally supply DC rectified from utility power. When utility power fails, the battery carries the load without needing to switch. With this simple though somewhat expensive system, some exchanges have never lost power for a moment since the 1920s.
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