Most forms of uninterruptible power supply (UPS) can be either powered by battery or flywheel energy. These are ready for immediate use at the instant that the

mains electricity Mains electricity or utility power, power grid, domestic power, and wall power, or in some parts of Canada as hydro, is a general-purpose alternating-current (AC) electric power supply. It is the form of electrical power that is delivered to h ...

fails, but the relatively small and finite amount of stored

energy In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of hea ...

they contain makes them suitable for short periods of use, typically in the order of a few dozen minutes to a couple of hours depending on the actual load. To get uninterruptible and continuous power supply, a diesel-generator back-up system is needed along with a fuel supply plan that includes on-demand replacement. Diesel rotary uninterruptible power supply devices (DRUPS) combine the functionality of a battery-powered or flywheel-powered UPS and a diesel generator. When mains electricity supply is within specification, an electrical generator with a mass functions as motor to store kinetic energy in an electro-mechanical

flywheel A flywheel is a mechanical device which uses the conservation of angular momentum to store rotational energy; a form of kinetic energy proportional to the product of its moment of inertia and the square of its rotational speed. In particular, as ...

. When mains electricity supply fails, stored energy in the flywheel is released to drive the electrical generator, which continues to supply power without interruption. At the same time (or with some delay, for example 2 to 11 seconds, to prevent the diesel engine from starting at every incident), the

diesel engine The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-ca ...

takes over from the flywheel to drive the

electrical generator In electricity generation, a generator is a device that converts motive power (mechanical energy) or fuel-based power ( chemical energy) into electric power for use in an external circuit. Sources of mechanical energy include steam turbines, g ...

to make the

electricity Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as describ ...

required. The electro-magnetic flywheel can continue to support the diesel generator in order to keep a stable output frequency. Typically a DRUPS will have enough fuel to power the load for days or even weeks in the event of failure of the mains electricity supply. The main advantages of DRUPS equipment compared to battery-powered UPS combined with a diesel-generator are the higher overall system energy efficiency, smaller footprint, use of fewer components, longer technical lifetime (no use of power electronics) and the fact it does not result in chemical waste (no use of batteries). The main disadvantages of DRUPS equipment are a more frequent maintenance regimen due to the number of moving parts. DRUPS are also typically installed in external buildings due to noise concerns from the generators. A DRUPS can provide a ride-through time of 15–40 seconds. A flywheel UPS can be installed ahead of typical UPS battery systems to reduce the effects of lightning & switching transients and to increase battery life.

References

Uninterruptible power supply {{Electric-power-stub

See also

References