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Friday, 18 March 2016

APC-UPS 430-7103 transformers repurposed

I have a few of these from disassembled UPS as they were decommissioned, the rest went to recycle these found their way to me. Initial findings:

Primary (dual windings) blue/yellow and black/white are the two pairs of windings.16AWG
Secondary thick black and white. 10AWG

Apply 230VAC to the black/white primary and obtained 15.05VAC on the secondary.
Pass the secondary voltage through a simple heat sinked square block 100A rated bridge rectifier and 35000uF smoothing capacitor across the output and obtained just a little over 13.13V DC with very little ripple. I will provide oscilloscope images later.

The transformer did not get hot to the touch even after about 2 hours providing 12VDC (rectified) at 26 amps using a bank of 12V 50W spots as a load. The current was measured at several points during the test. The 240AC feed was fused at 5 amps however, the current used was not measured.

As I have several identical 430-7103 units, I paired two up, so fed the primaries in parallel and the secondaries in series and no surprise 26.37V DC obtained using the same setup.

I believe these would make ideal 12V supplies or lower voltage variable bench supplies. Wire as a pair (which is how they are used in the APC UPS originally) they should easily provide the voltage headroom required for suitable regulation circuits and would easily provide voltages between 0 and 24V. Heatsinks will be required at higher current that might general heat. A voltage above 12V could be obtained using a buck boost DC-DC module rated appropriately with a single transformer.

I am sure the current handling capability of these will be well in excess of need.

I also have a couple of torroid transformers (do not look like they came from APC though, seemed to be using split primaries, expecting 110VAC on each winding, can connect in series to use with 230VAC and twin outputs (that appear to be identical). The output (two of them) were just over 28VAC, DC 24.85V and each managed >6A and >11A when connected in parellel.

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