Hello in schematics of ups in general I see a transformer at the mains side of the device, but as far as I know isolation transformers are at the output side of the ups device. So is there a situation in which we have two transformers ? İf not why I see xformers before the rectifier part in schematics ?Or I know it wrong and it (galvanic isolation xformer) is laready at the input side?
UPS İsolation Transformer
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ron
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They were originally for isolation. Not needed much anymore. Some used to like them for well cell storage and not VRLA type, but not really for a good reason imho.
http://www.apcmedia.com/salestools/NRAN-7NB2FG_R0_EN.pdf
http://www.apcmedia.com/salestools/NRAN-7NB2FG_R0_EN.pdf
tallgirl
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Transformers were also used for filtering, with ferro-resonant UPSs being popular back in the day. However, they are increasingly less popular as power supply and other load designs have changed.
See this paper, also from APC --
http://www.apcdistributors.com/white-papers/Power/WP-1 The Different Types of UPS Systems.pdf
See this paper, also from APC --
http://www.apcdistributors.com/white-papers/Power/WP-1 The Different Types of UPS Systems.pdf
brian john
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Some ups are only manufactured as 480 VAC in a 208/120 VAC facility you can have factory transformers on the input and output.
weressl
Esteemed Member
There are literally hundreds of possible combinations how you arrange your circuits. There are internal transformers and external ones on input, output and - don't forget - the bypass line.
When dealing with multiple transformers in series and parallel paths, it is possible that through phase-shifting you have a phase differential between your critical load and maintenance or other bypass. You can actually dump the load with the make-before-break mechanical transfer switch when paralleling your UPS with an out-of-phase bypass.
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