Voltage troughs
Voltage troughs are characterised by a drop in voltage amplitude over several periods. They are due to heavy electrical loads starting up such as engines, lifts, lighting, heating… and causing system shutdown and untimely failures.
Harmonics
Current and voltage harmonics are created by non-linear loads connected to the distribution network. Harmonic distorsion is a form of electric system pollution liable to cause problems if the sum of harmonic currents is higher than certain limited values.
Power line disturbances
Voltage drops to zero for a few milliseconds. These power line disturbances are induced by short-circuits caused by users on the building's network.
UPS
In short:
In IT, this word describes a peripheral that is connected between the power supply and the computer. By regulating the electricity input, it prevents power line disturbances or peaks that could cause data loss or damage the computer. When a power failure occurs, it replaces the power supply for a few minutes (depending on the capacity of the UPS), thereby giving you the time to save your data.
More information:
A UPS is not solely designed to overcome power cuts. Its role is also to stabilise the voltage and eradicate interference.
The UPS is an important link in the security of IT systems. Its main job is to takeover from the mains power supply when power cuts occur, giving users time to save the work in progress.
Power cuts are not the only incidents that these appliances are confronted with. Filtering, as well as regulating the voltage, also form part of the key functions to be provided.
A good UPS should not only ensure an uninterrupted power supply to the connected appliances but also a high quality power supply.
A UPS is made up of three parts:
- The rectifier, which converts AC to DC power designed to charge the batteries and supply the UPS.
- The batteries, which store the energy.
- The UPS, which converts the DC power supplied by the rectifier or batteries to 230 V AC power at 50 Hz, identical to the mains.
The UPS also comes with an automatic closedown software: in the event of a mains power failure this software (installed on the computer connected to the UPS) will automatically close down all programmes after having carried out any necessary backups.
Surge suppressor
A type 3 surger suppressor is a device providing electrical appliances with protection from transient overvoltages created by lightning in particular.
Line Interactive Technology
The principle of Off Line technology is improved since the input voltage is monitored and filtered by the UPS before being fed to the equipment.
The power supplied is therefore a higher quality. A voltage regulator enables quality power to continue to be supplied during major variations and without using the batteries whose useful life is directly proportional to the number of recharging cycles. A filter and surge protector increase the security.
When there is a power cut, the UPS switches to battery mode (switch over time <2ms) and a communication software takes charge of saving files and closing down programmes.
Line Interactive technology is recommanded in areas in which the mains supply is moderately disturbed (commercial zones or rural areas) and also chosen to protect servers, CAD applications and minor accounting tasks .
Off Line Technology
The hardware is normally powered by the mains, the UPS only taking over in the event of a mains power cut or major drop in voltage.
Off Line technology enables the protected appliances to be powered for long enough to save data and/or turn off the appliances correctly.
This switch over to battery power takes a little time (generally >4ms) which will not disturb computers with cutting power supplies, but it may cause a problem for more sensitive hardware (measurement instruments).
Off Line UPSs are the most cost effective. They are recommended for single station computers (PC-type) designed for office automation or games and small servers in an environment with little electrical disturbance such as an urban area.
On Line Double Conversion Technology
A permanent source of power is supplied by the UPS thereby ensuring a constant voltage and no interference. The appliance to be protected is therefore totally disconnected from the mains which means no switch over time and no power line disturbances.
In the event of a mains power failure a communication software will automatically close down all the programmes after having carried out any necessary backups.
Tests prove that On Line UPSs offer the most stable output voltage and the best immunity to interference.
On Line technology is particularly recommended in industry. It is also chosen to protect systems in which even the smallest loss of data is inacceptable, such as calculators, automatons, cash registers, major IT systems for example and more generally, any strategic applications, sensitive electronic systems and medical apparatus .
Variations in frequency
Sinusoidal periodicity is no longer constant. These variations, whether sudden or slow, are largely due to generator set speed variations and are very rare on public networks in developed countries.
