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Post by Dan1973 on Apr 28, 2014 8:38:25 GMT -8
Hi Gary,
I found a battered UPS near the dumpster in my home. I managed to salvage several relays and a decently sized transformer in good condition.
Id like to ask what's the best way to asses a transformer with unknown power ratings. Im looking for the suitability to use it for an inverter.
The only marking left on UPS device was 1000VA (the transformer itself is not marked) but judging from the size of the thermal radiator
on the MOSFETs , this may very well be a marketing exaggeration.
The device has 15.5-0-15.5 V and 27-0-27 V low voltage windings, and one 0-196-225-252 V high voltage winding. I did not managed
yet to measure the diameter of the 15.5 windings, but the outside wire coupled to the winding is AWG 10, which should be good for 15 amps.
The 220v winding on the other hand coupled through is 18AWG only.
Thanks, Dan
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Post by Gary Lecomte on Apr 28, 2014 18:54:19 GMT -8
Hi Gary, I found a battered UPS near the dumpster in my home. I managed to salvage several relays and a decently sized transformer in good condition. Id like to ask what's the best way to asses a transformer with unknown power ratings. Im looking for the suitability to use it for an inverter. The only marking left on UPS device was 1000VA (the transformer itself is not marked) but judging from the size of the thermal radiator on the MOSFETs , this may very well be a marketing exaggeration. The device has 15.5-0-15.5 V and 27-0-27 V low voltage windings, and one 0-196-225-252 V high voltage winding. I did not managed yet to measure the diameter of the 15.5 windings, but the outside wire coupled to the winding is AWG 10, which should be good for 15 amps. The 220v winding on the other hand coupled through is 18AWG only. Thanks, Dan Hi Dan, Being Registered is Better than being a GUEST. Where do you Live. USA or ? Possibly send me your Phone number to discuss this Easier? (By Email or Private Message) Is it an IRON Core Transformer or Ferrite Core? Length, Width & Height? Are the Winding: Solid Single Strand Wire, Stranded Wire or Litz Wire? Take care......Gary |
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Post by lamazoid on Apr 29, 2014 7:34:11 GMT -8
Why don't you use original UPS circuit for inverter? It's broken or what?
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Post by dan1973 on Apr 29, 2014 8:02:08 GMT -8
Why don't you use original UPS circuit for inverter? It's broken or what? Its broken beyond repair. PCB is split, wires where dangling all over the place, and it has some battery corrosion. |
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Post by dan1973 on Apr 29, 2014 8:28:52 GMT -8
Gary, I live in Romania in Eastern Europe, so a phone would be pretty expensive. I would call but I'm underemployed at the moment. But thanks for offering, you are very very nice. Very few people would have offered to help on phone. The transformer is an iron core, 100x114x60 mm. It weighs around 5kg (11 pounds). All windings are solid single stranded wire. 2 low quality photos:   And today when I came from work I found another UPS unit in the same place, probably dumped by the same people. This was a proper 3000W unit, was made in Italy, is SMPS based. Some of the power transistors are evaporated, a coil is badly burned, but there are a lot if things to salvage inside:   Thanks for any input. |
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Post by lamazoid on Apr 29, 2014 8:45:40 GMT -8
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Post by Gary Lecomte on Apr 29, 2014 15:28:23 GMT -8
Checking dimensions on a 750 Watt Microwave Transformer that I have,it is 120 x 100 x 50mm.
This is for Continuous Power.
Your transformer will probably do 1000 Watts in INTERMENTANT Use.
It will probably work in an older style of 50 or 60 Hz Inverter.
Yes My older type of Mosfet inverter (Above)is quite good
But Newer High Frequency Inverters using Ferrite cores are much Lighter and more effiecient.
MOST IMPORTANT on winding the 12 Volt Primary is it MUST be Bifilar Wound for Best Results.
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Post by lamazoid on Apr 29, 2014 21:33:34 GMT -8
I don't think that high frequency ferrite inverters are more efficient. Lightweight, yes, but compared with weight of Lead-Acid batteries it's nothing.
Ferrite inverter has two-stage conversion: 12v=>300v DC, then 300v DC to AC sinusoidal approximation, usng typically bridge inverter configuration. So the overall efficiency will be stage1 * stage2, plus dynamic losses in MOSFET and magnetic loss in ferrite on high frequency.
With low frequency transformer we have just one stage, AC approximation from square wawe is done via simple LC network. Low loss in mosfet and core, And plus very good overload immunity.
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Post by dan1973 on Apr 30, 2014 10:39:08 GMT -8
Thanks guys.
Also, I started to take apart the 3kw UPS, I dismantled among other things 4 ferrite cores Magentics 007A439A7.
(they are the ones on the row just above the white high voltage capacitors in second picture). They where seated on a support and immobilized with some kind of resin. Its relatively easy to remove the windings and get them out, but the cores have now residual resin and some burned residue from the single stranded wire isolation which burned on them.
Any ideas what solvent would work good to clean them for reuse ?
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Post by lamazoid on Apr 30, 2014 11:34:52 GMT -8
It seems unlikely that any solvent will work... just mechanical cleaning with some kind of brush and? maybe kitchen cleaning chemistry?  Anyway, if you already have the working iron transformer, why don't you seek for other usable components, like ICs ? i think dead UPS should contain everything needed to make simple AC inverter. Even regular logic ICs (like in Gary's design) will do. Other point to think about is, what actually you're going to power with that thing? Most of modern electronics does not require clean sine wawe input. |
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Post by dan1973 on Apr 30, 2014 13:32:23 GMT -8
It seems unlikely that any solvent will work... just mechanical cleaning with some kind of brush and? maybe kitchen cleaning chemistry? Anyway, if you already have the working iron transformer, why don't you seek for other usable components, like ICs ? i think dead UPS should contain everything needed to make simple AC inverter. Even regular logic ICs (like in Gary's design) will do. Other point to think about is, what actually you're going to power with that thing? Most of modern electronics does not require clean sine wawe input. I got 2 UC 3844, 2 UC 3524, 4 A3120 IGBT optical gate drivers, 10 or so LM 324 from that board. There are some Schmidt trigger inverters which I didn't desoldered yet. Tomorrow Ill scavenge for good diodes and check the IGBTs and power MOSFETS. A lot of chokes which can be reused and high voltage caps, I guess I can salvage the non-electrolytic ones. The inverter, I want to use it with some power tools and a laptop computer in a mountain hut in an area with no electricity. |
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Post by lamazoid on Apr 30, 2014 23:32:03 GMT -8
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In other words, control circuit should provide adjustable DEAD TIME option.