Guru
Joined: 13/10/2014
Location: AustraliaPosts: 2071
| Posted: 10:36pm 17 Apr 2025 |
I don't think the Duty Cycle changes, it's still the same Power level and winding ratio, only difference is that each Power Stage/FETS/Toroid are doing half the work of a single stage inverter.
If you wind a Toriod with the typical commercial "save money" turns ratio, you will often see the duty cycle really start climbing as the the Inverter tries to maintain the nominated AC output voltage under even smallish loads, and likely higher Idle power.
The other tell tail sign is a Toroid that needs at least 48V to get 240Vac output to regulate, the Idle Duty-Cycle can be as high as 92%, along with ever increasing Idle power.
I feel (could be wrong) that the real limit in Toroidal power ratings is the size of the wiring and heat, using a bigger core to fit heaver wiring of course means less number of turns, more metal, better airflow, and is therefore easier to keep cool, however keeping a smaller core temperature under control would be a problem, even if the windings could take the same power level.