Guru
Joined: 21/06/2018
Location: AustraliaPosts: 1251
| Posted: 01:11pm 26 Oct 2023 |
Hi sPuDd, sorry to bump an old thread, what did you do about your Toroid core search ? I am also in the process of creating and building up a 7kW continuous inverter that should easily handle peaks up to around 15 or 20kW. If you haven't solved this yet below is my proposed solution.
I am not keen to wind up a toroid from scratch and have been considering what approach to use for a while now. Before I went on holiday some months back I had recently bought 2 x complete 3.5kW Aerosharps ($50 each). They have a big Toroid, 195T 230V winding and a 212T 250V secondary. I propose to unwind 17T from the outer 212 turn secondary (making 195T) and place the 2 x 195T in parallel for lowest impedance.
If I do this to both toroidal transformers and then place one on top of the other and wind just a 13T primary that passes through & around both cores and parallel the 4 x 230V windings the result should be quite good, The primary is just 25mm square (or 32mm) PVC single core cable.
I initially experimented with a 25T primary on 1 toroid, which gave the best results, but 2 stacked toroids means the primary turns are halved. That is the basis for my solution, using 2 x professionally wound toroids (albeit with 17T removed from the outer windings), sure it doesnt give a big hole in the centre but it appears the 13T primary should be a cinch to add to the ~ 52mm central hole.
Stacking 3 such cores and using an 8T primary is also possible but would be hard to physically manage, the idling power for the 2 cores would be ~ 38W, 3 would be ~ 57W
If instead of removing 17T from the 250V winding you added 17T to each 230V winding and paralleled up all the 250V windings but ran the output voltage at 230V from the 250V windings, driven from a 9T primary, idling is a bit better at ~ 16.5W for each toroid or 49W for the 3 toroids.