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Re: Capacitor Help



Original poster: Ed Phillips <evp@xxxxxxxxxxx>


Hi Malcolm,

YES, however, the steady state response from spice using LTR of 1.6*Cres is close to that of an unloaded NST (I just cant remember whether higher or lower). It takes either a transient or feroresonance (as Ed mentioned) to get the voltage higher. Now that I'm thinking about the subject, it seems if ferroresonance occurs at 2.6*Cres, it will occur more at 1.6*Cres cause more of the inductive reactance of the transformer is cancelled by the capacitive reactance of the load (results in higher current limits) and the transformer inductance doesnt need to be reduced as much due to saturation. I just may experiment with this next summer to see where ferroresonance occurs with respect to Cp values.

Gerry R."

It is easy to get ferroresonance even if the capacitance is less than "Cres" based on leakage reactance calculated from ratio of rated terminal voltage to rated short-circuit current. The permeability is higher at low voltages than at operating voltage, or at least it was in my case. The particular experiment involved a 15 kV, 60 ma transformer with a 0.006ufd 30 kV mica transmitting capacitor across it. That's a lot less than "official" Cres. In thinking back I believe the critical primary voltage was less than 30. Anyhow, the high-voltage range on that poor VOM is still shot!

Ed