[Home][2016 Index] [TCML] oops - even old hands can miss things [Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[TCML] oops - even old hands can miss things

tl;dr - instelling a HV rectifier isolates the primary cap from the line side, preventing it from contributing to Power Factor Correction of the transformer


A short story of how even experienced coilers can lose track of their own design over long periods…

 I’ve been working on something I call “My Last Tesla Coil” for a long time, much longer than originally expected, but my life and employment went through some changes and I suddenly had a lot less time and money available to spend on the project, so it is has stretched into years.

 Anyway, the coil uses a large ( 120mA ) 15kV NST and I felt it would be appropriate to add PFC caps because my experiments showed that apparent current drawn from the outlet went down and so did breaker trips, so - worthwhile, although it didn’t seem to visibly affect performance.  The PFC caps have been installed in the control panel along with the HV xfmr for years. When I added them, I took into account the reflected capacitance of the primary circuit.

 Along comes the additional notion to prevent resonance in the coax HV leads heading out to the coil base by the simple - heh- expedient of rectifying the xfrmr output.   
(the resistors in the terry filter should also help prevent that resonance)

 Fortunately, I have some beastly rectifiers capable of handling the duty, surprisingly compact epoxy units, and I’ve been building a compact oil filled plastic enclosure with recessed HV terminals which can be tucked inside the control panel as well, despite how crowded it is already with the (isolated) front panel components, big “Terry filter” etc.

 It didn’t even dawn on me until last night when I was describing all this to a visiting EE friend that rectifying the xftmr isolates the Cp from the power line, removing its (reflected) contribution to PF correction.  Oh well, c’est la vie - it’ll be slightly less well corrected for now.

 - B(G)L
Tesla mailing list