Hi MarNet.
"230x100x70, this is 45.5cm/2
will be enough for a 5kw transformer?"
I found that the AirLink toroid cares 190 x 90 x 60, 2off doubled up, ran 4.5kW very satisfactory for a good period of time, but warmed up and needed cooling well. This OzInverter works well here and does the job.
So at 60cm/2 core, 100mm x 120mm section, I found that the core should have given with 14 turns primary about 30v, what we were aiming for. However it turned out 28.2v, which is okay and oztules commented about better headroom for the toroid on saturation. I think?
So my No 2, 8kW OzInverter, is having the 230 x 100 x 70, 2off stacked cores, giving me a good rectangular block of core so simplifying copper use and loss, but giving me a 90cm/2 of core, 130mm x 140mm section.
It also gives me that 100mm dia hole in the middle that gets my copper secondary and 14 turns of primary to sit in there neat and tidy, although I may go up to 75mm/2 thick for the primary.
"how exactly do you calculate the winding?"
'Frackers' has been studying the data on toroids, says his "head hurts", but oztules has the real working knowledge with his creations.
"the 50cm/2 toroid core" ...... 220.140.125mm, 80mm x 125mm section, "10kg weight? only? that will be ok for a 5kw inverter?"
Speaking with my limited experience of cores and the PJ toroids, I doubt if one toroid these dimensions would get 5kW without some serious cooling. Double cores might be good but you are using more copper as the centre hole is a big diameter. But also with this size the core section is not optimal.
Any way I am sure Oztules will comment further.
Pic shows my 2 off stacked/joined 190mm x 90mm x 60mm cores, giving me the 120mm height and 100mm x 120mm section. My observations make me understand that its all about optimizing the core Mass effeciently.