what value capacitor needed in circuit

[mikemongo101]

I have a circuit of 120v ac with a transformer 300va-isolation 120-120 and i need to add a capacitor after the transformer ( in effect a LC circuit).I want to use the capacitor to discharge into the gates of two SCRs at near 90 degree cycle to both turn off the transformer and isolate the primary circuit in order to harness the CEMF and dump it into the secondary circuit at the same time it is receiving its own CEMF. my problem is that i need to know what value cap to use and i need to know how to figure that value. I may have to include a trimmer pot to hit 90 at Prms. The mains 120v 90 to 180 will be in isolation in a delay phase input to another transfomer mirror circuit. thanks many!

mikemongo101

 

[mikemongo101]

the formula was 1 / 6.28xfrequencyxZ = C

thanks anyway

 

[neon]

how do you intend to shut off scr if conducting?