Great advice. Thanks. The switching frequency is 100Khz. The output inductor sees 200Khz but the resonant inductor because it is on the primary and before output bridge , sees 100kHz. Based on the loss and saturation curves at 100kHz the saturation and loss both are limiting factors. I'm trying to keep delta B below 300mT. Based on my calculation the core won't get high with this much flux.I've used both a Micrometals T130 Yellow/grey (RF catalogue not power catalogue) and a gapped ferrite in the past for resonant chokes in PSFB converters. I prefer the gapped ferrite like Warpspeed suggests. It gives you more freedom to fine tune the inductance, if required.
Just remember that at 200kHz you will be loss limited and not saturation limited and to get the loss to a reasonable value you will probably have to limit your flux swing to way below 200mT peak. Check the graph "Power loss vs freq" for different flux densities and keep below about 1kW/m^3 and it shouldn't run too hot. Obviously use a low loss material. There's an exponential (Steinmetz) relationship between power loss and flux density at a given freq. Don't worry too much about using a custom gapped ferrite that has a gap way bigger than is available as a pre-ground gap. This indicates that you are using to core effectively.
NB. If you decide to use a Micrometals core be wary of cheap Chinese counterfeit versions.
unfortunately the above is not quite correct B = uH = uo.ue Ni / Le i.e. B is directly proportional to I, in a choke it is the current, in a Tx it is the magnetising current (not the load current).Flux swing in the core is entirely a voltage phenomenon, current has absolutely no effect and can be ignored for pure ac applications
The discussion here is mainly about choosing a core material, and relevant flux swing in an ac application.if you know the current - you don't need to know the voltage either, this is the other side of the coin, if you are totally ignorant of the current then you cannot factor in things like the source impedance of the driving circuit... and associated volt drop...
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