Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx> Hi Mike,
Original poster: "MIKE HARDY" <MHARDY@xxxxxxxxxx> back to unity. With Cp values even larger, the voltage gain becomes less than unity (the transformer can not charge the Cp to full voltage). So is it ok to use a Cp larger than LTR? If the cap can't charge all the way, doesn't it just act like a cap of suffucuent value?
Good question. Theoretically, Cp larger than the "official" LTR should be just fine. However, this statement assumes that the NST stays linear and doesn't saturate. Once the NST core starts saturating, the effective current limiting inductance is decreased and current out of the NST goes up. There is a phenomenum called ferroresonance (you can google for this) that describes this in more detail. I have experienced this first hand on a NST driving a large capacitance (2.6*Cres) with the SRSG removed from the picture. I haven't looked for it with a 1.6*Cres cap, but a properly set sparkgap taking energy out of the system should prevent uncontrolled rise. I have heard of two cases of static gap TC systems consuming much more line current than they should (both were using large Cp values - maybe 3.0*Cres) and I'm wondering if ferroresonance is part of the problem.
Gerry R