Hopefully? Another 48vdc-240vac Toriod Inverter build.

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analog8484 Senior Member Joined: 11/11/2021 Location: United States Posts: 141	Posted: 05:39pm 24 May 2023         KeepIS said   Apology for my long ramblings, but it's more a recap for me for when I look back in the future: No need to apologize.  I personally think your explanations and discussions are way more valuable than the actual inverter build documentation which is also very valuable.  Much appreciated.   KeepIS said   How stiff you wind the primary and secondary, how big the Toroidal Core is, DC coupling losses, wiring losses, and the list goes on, all can effect the exact value of inductance required, and all can effect how severe the Toriod reacts to various complex load conditions. I agree the inductances/reactances can dynamically change to some degree in the system. However, that still doesn't seem enough to explain the severe effects of certain (mainly non-linear?) loads.  Learning more about transformers, I see all the factors (e.g. winding stiffness, etc.) you mentioned do affect the transformer inductances, resistances and capacitances but they are all relatively static properties in a built system.  So, the question I want to get answers for is which ones can really have sudden severe effects under non-linear loads?  And what is the process? After some further research, my theory now for the likely root cause is specifically the interaction between the primary choke inductance and the transformer mutual inductance.  The primary voltage is positively dependent on the transformer primary inductance and current change rate and negatively dependent on the mutual inductance and secondary current change rate.  Under non-linear loads, the secondary current change rate can suddenly increase drastically.  The effect of this increase is that it will have large negative effect on the primary voltage that will in turn drive large increase in the primary current rate of change.  The large change in the primary current will be resisted by the primary choke.  Therefore, if the primary choke inductance is too high the result is the observed sudden severe effects.  For me, this also explains the observation that a relatively small non-linear load can have similarly severe effects as a large non-linear load.  It's the current change rate that matters rather than the current magnitude. If this theory is accurate then a likely key design limit for the choke inductance is the max secondary current rate of change.  I wonder what is the max secondary current change rate (100A+/us?) when your air-con is running.