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Re: [TCML] Phase tuning gadgets and when to set the gap to discharge.



The motor I have works pretty good and doesn't slip, it's 
a simple propeller gap swinging a 1/4"x7" long rod of 
tungsten between four electrodes on the corners of a square.
Standard 120 bps system.

Under my timing light the electrodes appear stationary and
don't appear to rotate so I know it's in sync. They're just
not stationary at the right position. :)

The motor has a start capacitor, is that still required with
the phase shift circuit, in addition to the capacitor paired
with the variac?

--- On Wed, 7/2/08, futuret@xxxxxxx <futuret@xxxxxxx> wrote:

> From: futuret@xxxxxxx <futuret@xxxxxxx>
> Subject: Re: [TCML] Phase tuning gadgets and when to set the gap to discharge.
> To: tesla@xxxxxxxxxx
> Date: Wednesday, July 2, 2008, 6:09 PM
> The issue with the small oriental motors is that they're
> so
> 
> weak that they need a?light-weight rotor to permit them to
> 
> go into sync.? 
> 
> The proper phase setting depends on both the particular NST
> used,
> and the cap value used.? It would be hard to predict or
> calculate this.
> Best to just adjust for longest sparks.? For a 120 bps sync
> system,
> an LTR value cap must be used for the Tesla tank cap, for
> best
> results.? 
> 
> The proper cap value for the phase shifter circuit is
> around
> 3 or 4uF if I remember correctly for the small oriental
> motor.
> The proper value will give a 5volt resonant (above line
> voltage)
> rise across the
> motor terminals (max) at some point along the phase
> variac's travel.? A 10volt rise is acceptable also.?
> The proper
> value phase cap is selected by trial and error by measuring
> this resonant rise across the motor terminals.
> 
> 240 bps will generally give shorter sparks, and would
> require that
> additional electrodes be added to the rotary gap.
> 
> ??? ?http://futuret.110mb.com
> 
> Cheers,
> John
> 
> -----Original Message-----
> From: Jeremy Scott <supertux1@xxxxxxxxx>
> To: tesla@xxxxxxxxxx
> Sent: Wed, 2 Jul 2008 5:52 pm
> Subject: [TCML] Phase tuning gadgets and when to set the
> gap to discharge.
> 
> 
> 
> 
> Hi all,
> 
> I designed and built a simple circuit to help adjust the
> phase of SRSG's.
> 
> It's a timing light (white LED .. fancy) that pulses at
> 120 pps at each AC zero 
> crossing.  The pulse width is less than a millisecond or so
> with 
> half of it before and the other half after the zero
> crossing. Kind of like
> an inverted rectified full wave if you can imagine that. 
> 
> It uses a 120VAC to 9VAC power adapter/transformer that I
> found in my junk box 
> for the signal and power. It's a fairly simple
> two-transistor circuit.
> 
> Turn the lights out, shine it at a rotary spark gap, and
> you can see if the 
> electrodes line up like they should and if your motor is
> truly synchronous.
> 
> So I used it on the propeller gap of my first coil which
> was tuned right but 
> never worked very well. Hah. Way out of sync. Not at the
> zero crossing and not 
> at a peak, but somewhere in between.
> 
> I tried it with the SRSG phase adjust variac thing as
> discussed previously on 
> this list and turns out the adjuster isn't doing
> anything. (Anyone know the 
> proper size capacitor for one of those small square
> oriental motors?)
> So now I know why my first coil sucked and I can fix it!
> 
> So I guess I got a few questions, now that I can visually
> see at which point in 
> the AC cycle the gap is firing at. 
> 
> 1. So now that I can actually see and adjust the timing,
> when is the best time 
> to have the gap fire, theoretically? (I know practically,
> it's 'whatever' ... 
> adjust it while running until the streamers get bigger.)
> 
> Is it at the zero crossing when the capacitor has had a
> full 8.3 ms to charge OR 
> is it 90 degrees (4.16ms) sooner/later when AC cycle has
> peaked
> in voltage?
> 
> For any given input current (say 60ma NST), would it be
> better to pick a larger 
> capacitor size that takes a full 8.3 ms to charge then
> discharge it into the 
> tank before the current reverses (at the zero crossing) 
> 
> OR would it be best to have a smaller capacitor and
> discharge it at the peak 
> input voltage but potentially wasting the rest of the
> current available in the 
> half cycle? (eg. step up the break rate to 240bps and fire
> the smaller capacitor 
> twice.)
> 
> 2. Is the timing light even accurate? The signal I'm
> using comes from a step 
> down AC wall adapter. Is the secondary phase angle from
> this small transformer 
> the same as the phase angle of the high voltage 15K
> secondary of the coil's 
> transformer?
> 
> 
> 
>       
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