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Off-line UPS.
The most basic forms of UPS. They utilise a simple filtering system to remove spikes, surges and some electrical noise.
Very often "pseudo" or square wave output in battery operation. Typical transfer time between 2-6ms.
An economical solution for non critical IT and process equipment where the output sinewave and frequency are not crucial to the protected equipment.
Single phase only, VA ratings from 250VA to 800VA. Typically fitted with internal batteries to give 4-9 minutes runtime upon mains failure. Because of the limited input window for voltage and frequency, they will often revert to battery operation should a site generator be utilised.
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Line-interactive UPS.
This type of UPS have been designed with a superior filtering capability and transfer time than off-line UPS (Typically 2-4ms). They also have a wider input voltage and frequency window. Output can be either sinewave or pseudo sinewave when operating on battery.
Utilised more frequently than off-line types. Ideal for applications where the short 2-4ms break will not cause a problem.
Single phase only, VA ratings from 600VA to 6kVA floor standing, 19" rack-mount units up to 6kVA. Typically fitted with internal batteries to give 5-15 minutes, but models are now appearing with additional external batteries to extend this runtime to up to 2 hours.
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On-line UPS.
Also known as "double conversion", the incoming mains is converted into two levels of DC, one to the inverter the second to supply the battery charger. The inverter changes the DC into a "clean" AC supply to power the load. When the mains fails the inverter instantaneously draws its DC supply from the batteries.
This double conversion method allows the UPS to eliminate most of the sags, surges and brownouts normally found on a typical mains supply. EMI/RFI filters remove the spikes and "noise" generated by other electrical equipment.
This type of UPS also incorporate an internal static by-pass switch, designed to protect the UPS from overloading and also to protect the load from UPS failure during normal operation. This feature is not present in off-line and line interactive type of UPS.
The VA ratings for this type of UPS are from 500VA up to 5mVA (Parallel systems), 19" rack-mount units up to 3kVA. Both single phase and three phase applications.
Runtimes vary from several minutes with internal batteries to several hours with external batteries.
Typical applications are where system downtime is not acceptable. On-line UPS, because the input voltage and frequency window is greater, they are more favourable to work alongside site generators.
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No break UPS.
Designed around a "ferro-resonant" transformer, this type of UPS is designed to completely isolate the incoming mains from the output load. It utilises full-time power conditioning and galvanic isolation.
This type of UPS has a very wide input voltage window making it ideal for environments where there are wide fluctuations in the quality of mains power or for use alongside generators. This allows the UPS to operate even in the harshest of electrical environments.
Sinewave output on battery operation with a seamless transfer from mains to battery operation.
VA ratings from 500VA to 18kVA, with 19" rack mount units to 7kVA. Single phase with typically 10 minutes internal batteries to several hours with external batteries.
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