Double Conversion UPS, Part I – STM

After a long hiatus, Old School Tech has posted the first article in a new series, this time about creating a double-conversion uninterruptible power supply, which is useful for driving loads such as freezers or mission-critical items. Like a computer UPS, this power supply waits, fully-charged, until it is needed. Unlike a computer UPS, however, it produces clean, pure sine wave power.

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One Response to Double Conversion UPS, Part I – STM

  1. WiscoDave says:

    Passed on to an Extra class I work with. Here is his reply:

    “Nice article, thanks.

    You might also be interested in an old concept hams have been known to like, which is leveraging an old lawn mower engine to drive an old alternator to float an old battery. This powered comms, which seems efficient since for comms you really want 12v DC which that solution provides natively without an inverter. Traditionally, a generator makes AC, which has to be converted to DC with some sort of power supply, which is a more lossy conversion. You can then drive an inverter off the battery if you wish. I seem to recall one guy built his onto a wagon so he could move it around easily. Of course if money is no object, one of those quiet running Honda generators are nice.

    Another important consideration for comms anyway is the “dirty” nature of AC inverters (even pure sine wave ones), switching power supplies and solar charge controllers. They can be serious RFI (radio frequency interference) generators, so one has to be careful with the selections and do a lot of ferrite bead choking on all the power leads and test it all out before crisis time. About 5-10 years ago I purchased an (expensive at the time) pure sine wave inverter for the car which rendered my HF radio operation in the car completely unusable (constant S10 noise). Note, when I say comms I don’t just mean two-way radio equipment. A simple AM/FM radio should be standard equipment in a disaster in order to find out what’s going on. What good is that if your radio is swamped by RFI? Yes, you can run the radio off of batteries and shut your inverter off, but that may be incompatible with your goals at the time.

    I bought some solar panels and a charge controller about 5 years ago to play with that technology. My thinking at the time was in the event of a crisis, getting gas could be a problem.”

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