Senior Member
Joined: 11/12/2020
Location: CanadaPosts: 138
| Posted: 04:23am 31 May 2024 |
Transformer
So since getting the initial system working, I have been considering my options for a larger main transformer.
I have lots of the original size transformer (about 600va), which I had scavenged (they had too much noise for the intended application),
and I stripped off the copper off some of them with the intention of removing and rebuilding the laminations.
That would be a huge amount of work, with a bit of uncertainty, since unwinding and rewinding the laminations could result in higher core losses.
So fortunately I found a great deal on a pair of 1500va Hammond 1182T117's on a local buy/sell.
These have 4 120v windings, which I connected in series parallel to form the 120/120 volt output.
Hammond transformer vs 600va transformer
I added a couple of turns to the 120v primaries to give them the same ratio as the 120v secondaries and then added 7 more turns to improve the standby draw slightly.
I then added the new primary using #4 welding wire. To get the wire to fit, I removed the insulation, and replaced it with a layer of heat shrink.
I used a large neo magnet with a center hole, to pull a steel slug with attached string through the heat shrink.
I then pulled the 55' of wire through the 3/8" shrink tubing. A bit of a hassle, but it allowed me to get everything on there.
The DCR of the 240v winding ended up being .165ohms and the 47v winding .0131ohms. I used a 5.1:1 turns ratio.
I built an complicated mount for the transformer, that would have air flow around as much of the transfomer as possible.
I have not tested it yet, so we will see if it works or not.
Since our typical hourly draw is ~1kw with peak hourly at 2.5kw (not including A/C), I think this transformer will be large enough to support things.
I can always modify the second transformer to support A/C if global warming continues at it's present rate.