Guru
Joined: 22/10/2019
Location: AustraliaPosts: 952
| Posted: 02:04pm 11 Apr 2021 |
There's not a lot to report but I should still update my log.
I've wound the first winding for each of the transformers #2, #3 and #4 and am starting on the big daddy #1.
I have two larger 3kW cores stripped and ready to work on. I plan remove at least 20mm from the centre ... from 100mm ID to 120mm to allow a 5mm spacer between the core and the secondary winding ... and allow my substantial secondary windings to fit.
The secondary will be six layers of 1.8mm wire and I have a large roll of new wire to use, which will make a change from all the crinkly secondhand stuff I used on all the rest.
I also plan to use material from two more toroids to add to the outside of the 3kW cores.
There's been a bit of a holdup as I built a spot welder to use to tack the core material beginning and end to keep them nice and tight.
The first one I built from a microwave oven transformer by cutting out the secondary winding and fitting a low voltage one.
It simply did not have enough power so I've bought a small arc welder, stripped the secondary off that tx and wound a new one. Looks pretty gutsy and I expect it to work ok but I haven't quite finished it yet.
In the meantime, some photos ...
First is of the two 3kW cores ... and then of all the fibreglass binding material they used to insulate the corners etc.
The cores are really rough and both look like they were stored out in the weather before they were originally wound. Quite rusty and even bumps and scrapes on the edges which should have been dealt with before winding.
This is not very clear but it is of the welding of the inner part of the core. It actually feels worse than it looks ... and it looks bad enough. It's like someone dropped the handpiece in there and the thing arced and sparked around burning and melting everywhere. It's a mess.
This shot shows that the core is not continuous!!! There are dozens of joins in the whole thing. Here you can see three ... but there are lots more everywhere.
I recall seeing a youtube video of someone winding a core on a hand operated device and adding short lengths of core material all willy nilly ... somewhere in SE Asia. I think he was the guy who made these.
I'm keen to see how the other brand of transformer core is put together but haven't stripped the final layer of mylar off them yet.
