Why do they continue to use iron core transformer in UPS?

when you are going to rectify to DC high freq is nice because it is easier and cheaper to filter.

when you are going to drive equipment designed for 60 Hz the output needs to be 60 Hz.

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The output IS 60Hz either way. The typical 12V to 120V travel inverter have more steps: DC 12V --> hundreds of KHz AC-->stepped up to HF AC using light weight ferrite transformer--->rectified to high voltage DC--->MOSFETs chops it into 60Hz AC

The typical UPS inverter: DC 12V--> chopped into 60Hz AC-->iron core transformer steps it up to line voltage

|> > There are a handful of 12V to 120V AC inverter that uses a low |> > frequency switcher and an iron core transformer, but most of them are |> > two staged high frequency type. The first stage is a DC-DC converter |> > that makes high voltage DC and the second stages chops this into AC. |> >

|> > I've yet to see a computer UPS utilizing the high frequency inverter. |> > Even the very inexpensive ones uses a low frequency switcher and an |> > iron core transformer. |> >

|> > Is there any reason a high frequency inverter couldn't be used? |> |> when you are going to rectify to DC high freq is nice because it is easier |> and cheaper to filter. |> |> when you are going to drive equipment designed for 60 Hz the output needs |> to be 60 Hz. | | The output IS 60Hz either way. | The typical 12V to 120V travel inverter have more steps: | DC 12V --> hundreds of KHz AC-->stepped up to HF AC using light weight | ferrite transformer--->rectified to high voltage DC--->MOSFETs chops | it into 60Hz AC | | The typical UPS inverter: | DC 12V--> chopped into 60Hz AC-->iron core transformer steps it up to | line voltage

You are expected to carry the travel inverter around. This is not commonly done with a UPS. So the weight likely the relevant issue.

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The high frequency type cost LESS to make as well. Lower cost, lighter weight(saves them $$$ on shipping) means more profit. Unless there's a technical reason, I can't see why they won't use the high frequency design.

Higher frquency requires more filtering capacitors. At such high levels, there is more RFI. So with 10 times the power, you need MORE than 10 times the amount of filtering.

Still, technologies are improving, and the boundary where different choices work out better keep moving. Still, I would prefer a good solid iron core transformer for converting the voltage of clean sine wave power for those things that still require it. But that set is also shrinking.