RSG cap sizing (RE: Coil Design for Review)
I'm not sure anyone can say what the maximum, safe gap width is that will
apply to all situations. Much probably depends upon the condition of the
NST. Your mileage WILL vary. However, I must disagree with the blanket
statement that a synchronous gap will result in less strain on one's NST.
In addition to the NST voltage rating, the peak cap voltage is also
dependent upon the cap size. Using too small of a cap (or mis-timed rotor
phase) in a sync RSG can just as easily result in cap/NST over-volting as in
using a too-wide static gap. This is why it's very important to use a
safety static gap in parallel with an RSG.
Not enough has been said and published about the importance of using a
correctly sized cap with sync RSG's. Short of using simulation or direct
measurement, I know of no formula that one can use to ensure that a cap is
correctly sized to charge to safe levels. The newly discovered
"inductive-kick effect" really complicates this. A cap size that's right
for a static gap is almost certainly too small for a sync RSG. Would-be
users of sync RSG's should be cautioned that this is not a simple solution
that will in itself, guarantee safe operation.
Regards, Gary Lau
Waltham, MA USA
Original Poster: "Dr. Resonance"
Max gap for NST should never exceed 0.25 inches. We usually
around 0.170 inch max --- beyond this you will start losing
they are not designed for this type of work. A synchro
rotary 1800 RPM 4
pole would give you better output with less strain on your