Transformers are more simple than boost circuits would this http://catalog.triadmagnetics.com/Asset/TCT40-02E07K.pdf make the 240Vrms if low voltage side has 24Vdc chopped into it at 40-55hz?

Or can a current sense transformer do the same 240Vrms but with different primary voltage and at different frequency?

https://www.mouser.com/datasheet/2/597/cst2010-1223901.pdf

 

make the 240Vrms if low voltage side has 24Vdc chopped into it at 40-55hz?

Can. But the maximum current will be less than 0.133 A.

Or can a current sense transformer do the same thing but with different primary voltage and at different frequency?

So better not to do.

 

Transformers are more simple than boost circuits would this http://catalog.triadmagnetics.com/Asset/TCT40-02E07K.pdf make the 240Vrms if low voltage side has 24Vdc chopped into it at 40-55hz?

Yes, that would work for a very simple low frequency Square Wave type, 24 Volt DC to 240 Volt AC Inverter, at 40 Watts maximum.

Actually, you are making an isolated boost circuit - a Forward Switching Inverter
Many "Modified Sine Wave" inverters use this exact technique

 

You get problems trying to feed square waves (chopped DC) into transformers that are made for low frequencies, effectively the transformers "have to round off the square waves" themselves, so they get rather hot. You also get issues with things that you are trying to run from the 240VAC not liking anything but a pure sine wave signal. What your trying to make sounds like an "inverter", that are very common for mobile homes and caravans, theres a lot of info out there on how to do it, and how not to do it. (They are also quite cheap!) Usually you create a "pseudo" sine wave from your low voltage DC and feed that into a step up transformer.

 

Or can a current sense transformer do the same 240Vrms but with different primary voltage and at different frequency?

Yes, this could be used to make a higher frequency Forward type DC-to-AC Switching Inverter

 

Does it really mean it can make high power and high voltage from chopped square waves?

No. This transformer is only for current measurement. Its full power is very small. In addition, the range of its operating frequencies 10-1000 kHz.