Re: Weird SRSG turn on

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Gerry Reynolds" <gerryreynolds-at-earthlink-dot-net> 

Hi John,

 > Original poster: FutureT-at-aol-dot-com
 > >
 > I assume your electrode spacing is close at about 0.010" or so?
 > A very wide spacing can cause erratic operation.

It is about .035 right now cuz it rotate the motor in its carrage with loose
clamps while the motor is running and I don't want to risk a crash.  Being a
cap start motor,  the start torque is enough to cause it to rotate on its
own with the clamps loose so I just dont shut down the motor during
adjustments.


 > Some combos of NST and cap value can cause a voltage reversal mode
 > firing that draws a lot of amperage due to a very bad power factor.
 > Generally larger cap values will tend to suppress this undesireable
 > operating mode.  Often the best phase position shows the firing
 > to occur somewhat after the peak cap voltage is reached.  The voltage
 > is already beginning to fall at this point.  Wide safety gap settings may
 > be needed to perimit this to occur.  Some NST/cap combos may permit
 > firing at the peak cap voltage level.

I think my problem is the safety gap behavior.  The RSG seems to be doing
its thing OK.  It runs OK when firing 0.5ms after peak so I'm getting some
inductive kick.  I just can't get enough kick to bring the firing voltage
back up to 21KV (at 2.5*Cres) without the safeties firing.  Once I
characterize the safeties at its current setting, I will reset them and try
again.  (I borrowed Terry's HV probe so now I have two probes (same make and
model) to try a differential measurement.  First I need some warm weather.
The mountains got 2 foot of snow last night and it's raining all day today.

Could you explaing voltage reversal mode firing.  I have each NST fused at 8
amps and they didn't blow.



 > Since each NST brand is different and the applied voltage affects
 > the phase, etc, the simulations may not be correct.  I would suggest
 > adjusting the phase over a wide range to see what works best.

I've already done that and it runs smoothly when before peak, at peak, and
as late as 0.5ms after peak.  Best performance is at the 0.5ms level but I
can't charge to full voltage at 2.5*Cres.  I get full voltage at 2.0*Cres
and better performance.  The thing thats keeping me from fully charging the
2.5*Cres, I think, is the safeties, so I will try to widen them up some.



 > I've found that the safety spark gaps should be set rather wide for
 > SRSG systems.  For example on my TT-42 TC, I set the safety
 > gaps at about 7/16" for each safety gap for a total of 7/8".  This
 > is using steel washers on edge.  Large diameter gaps can of
 > course be set closer.

I'm using carrage bolts for the safeties, and I do believe I have them set
closer that 7/16.


 > The phase will need to be different as the variac voltage is raised.
 > In other words the phase setting that is best for a 20" spark output,
 > will not be best for a 40" spark output.

I noticed that too.  I think the inductance of the variac is causing the
phase shift.  When the variac setting is 120VAC, the inductance is a
minimum.  As the output is lowered, the inductance increases.


 > I would think the single ended measurements would be OK.

I shall try to confirm this with the differential measurement.



 > Gary Lau's 15/60 NST srsg coil gave 66" sparks at Ed Wingate's
 > Teslathon, and the sparks could have gone farther.

Cool,  I got 59 inch sparks with a static gap, but only able to get 42 inch
sparks with the SRSG, so if I can fix the safety gap problem, I'll have
something to look forward to :-))

Gerry R.