RE: [TCML] Coil V4 fail

["Phil Tuck" <phil@xxxxxxxxxxx>]

Stephan,
As has been pointed out your SRSG is just not quenching effectively. The
size of the electrodes at 4mm for 10Kva is far too small. They need
increasing to ideally 0.5 inch or 12 mm (As Dr R has said) and the heat
sinking needs to be greatly increased on the stationary electrodes as well.
Hot electrodes do not aid quenching, so yours are in definite trouble! I
don't know what size your propeller gap is, but increasing the electrode
diameter may also mean the dwell angle then suffers, in which case you may
need a bigger RSG altogether: hopefully that won't apply. Big coils, big
power, and big sparks mean big money as the peripherals soak up the cash.

That drawback with propeller gaps is getting the large diameter rods in long
enough lengths (if you are outside the USA); hence, the 13M type
arrangement. 

In addition, your big cap is almost certainly not being fully charged, even
with 950 mA available. I would have thought 150nF would be more than enough.
Too big a cap, assuming it fully charges, will also affect the quenching as
well. Other owners of coils your size will be better qualified on that point
to comment maybe.

The height of the secondary in relation to the primary sounds in the region
of being 'normal' if there ever is such a thing. 
Put your coil into Bart's JAVATC and get the coupling figure from that. This
will also tell you the best coupling figure to aim for as well. You can also
play around with your primary turns in the program as well and this allows
you to decide if you want to lower the coupling by raising the secondary, or
removing an inner primary turn. 

There is also a lot of wood around that primary, so check you are not
tracking anywhere. Wood is a next to useless as an insulator, varnished or
otherwise. Tesla had no choice, but we do.


Regards
Phil

www.hvtesla.com


-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of Teslalabor
Sent: 18 October 2010 15:22
To: Tesla Coil Mailing List
Subject: Re: [TCML] Coil V4 fail

Hi,
really no one has any thoughts about my new TC and its melting SRSG, because
of its energy transfer problems?

Here again two videos and the specs of the system:

http://www.youtube.com/watch?v=3pUh3UVZdiE

http://www.youtube.com/watch?v=Abr3rxYUH5o

In my opinion the sparks should be far longer.

Input: 0 - 400V 20A from variac
Tank circuit: 4 PT's each 100V / 10000V. Connected in series on low voltage
side and parallel on high voltage side. So if variac is on 100%, every PT
gets 100V and delivers 10kV. They are ballastet on the LV side via a ballast
inductor with air gap, so that the short circuit current without tank
circuit is arround 950mA.
Caps: 2 commercial BOSCH Pulse Caps each 25kV / 500nF in series, giving 50kV
/ 240nF measured.
Gap: Propeller Gap:

http://www.youtube.com/watch?v=O84SI50g0NY

Secondary is 25cm diameter, 1,5m long
and wound with 0,5mm wire + 0,4mm spacewinding.

The following problems: I think the coupling is to tight. Actually the lower
turn of the secondary is 3cm ABOVE the flat primary. When I put it lower, I
get bad racing sparks on the secondary surface.
Should I remove some inner turns of the primary, so that I can put the
secondary lower? Would this prevent the racing sparks?

Next possibility: Is 240nF to much capacitance in this TC? The matched
capacitance for resonance at 50Hz are 318nF, so I actually run the system
slightly STR. I have some more of the pulse caps.
Should I put a third one in series? Then I would get 166nF tank capacitance.

This would increase the bang voltage and so the bang size, of course I would
have to change the firing of the SRSG some ms earlier. Would this decrease
the gap losses and so solve the heating problem of the SRSG?

Best Regards
Stefan 

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