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Forum Index : Electronics : Inverter Transformer Question
| Author | Message | ||||
| Solar Mike Guru  Joined: 08/02/2015 Location: New ZealandPosts: 1138 |
Hi Have been following the OZ Inverter projects with avid interest and have a general question about using multiple low frequency transformers. With multiple cores would it also work to build as series connections with say two cores and having 1/2 primary and secondary windings on each core, then serial these together in correct phase; this perhaps would allow bigger wire to be used thus cutting down the losses. Its difficuilt here in NZ to obtain suitable large toroidal cores for an 8 KW inverter, but smaller ones as used in 2 - 3 KVA variacs are easier to get hold of. These however have quite small inner holes, so wire size is the issue. I am just about to start on my inverter project.. Cheers Mike |
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oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Yes you can, but better to glue the cores together, and then rewind... this will really cut down the losses, as you save 1/4 of the wire you would have for two separate ones seriesed. It is sobering to realize that we only use bigger cores..... so we can use more copper... That means that it is not technically the size of the core that designates the power, it is the copper losses that dictate the ratings, and how fast you can dissipate the heat from the losses..... and this usually means a bigger core so we have less turns of heavier wire. It is not uncommon to series the primaries, and parallel the secondaries. It is also worth wondering about how you will use this thing. If you really only have light loads ( <1000w) most of the time, and only run heavy loads of say >3kw for short times, then a 3kw transformer may be all you need. It is not worth making a huge one, if you not going to use it. The 3kw one will easily do 10kw startups, and 3kw continuous.. you may not need as much as you think, providing you can start huge loads, and support say 6kw for 10-15 minutes without too much heat. ...........oztules Village idiot...or... just another hack out of his depth |
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| Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138 |
Thanks for that clarification oztules, I do have some large startup loads to worry about, 2HP saw bench, big air compressor, 2 fridges and a freezer, not sure what the load would be if both fridges and deep freeze happened to start simultaniously. So I'm going to opt for as large a rating within reason. Guess you guys have all seen these, no idea of the quality but looks reasonable. https://www.aliexpress.com/item/1PC-48V-3000W-Pure-Sine-Wave-Power-Frequency-Inverter-Board/32687685774.html https://www.aliexpress.com/item/1PC-24V-36V-48V-60V-1000W-2000W-3000W-4500W-Pure-Sine-Wave-Power-Frequency-Inverter-Boar d/32697164098.html Cheers Mike |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
They work well.... not enough capacitor, so not sure of heat from ripple though. I have seen 5kw without a problem with them. ......oztules Village idiot...or... just another hack out of his depth |
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Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Has anybody tried running the Toroid in transmission oil? You can dissipate a lot of heat either with a simple tank, or add other cooling such as fins. It would not be hard to weld a Aluminium tank and add external fins or bolt on Aero-sharp heat sinks. Better still make a tank out of the heatsinks welded together, that combined with a few fans would run very cool. Or is that just madness? Or go big like this guy is making, I am sure 100's of KW's would not be an issue. Toroid winding There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138 |
It would work very effectively to cool it, years ago when I worked at the BCNZ transmitter site many of the transmitter transformers were oil cooled, didnt stop them from blowing up though and messy to repair. Transformer oil is probably hard to get, we used get it in 44 gal drums from Shell Oil, I would use a thin vegitable oil like rice bran oil as an alternative rather than transmission oil for DIY use. Mike |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I meant to say Automatic Transmission oil, it is quite thin, doesn't the proper transformer oil have all sorts of nasties in it? There are only 10 types of people in the world: those who understand binary, and those who don't. |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
I think the new stuff is basically biodiesel. or like a silicon brake fluid. quite a few companies sell it down to 5 litre containers. the old stuff was PCB based. I'm confused, no wait... maybe I'm not... |
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