Hi Chris,
Wow! 23 amps at 140 volts. That is 3.2 KW. I am surprised that your 20 amp circuit breaker doesn't blow. I guess the slow-blow action of the breaker prevents this especially since you are pulsing.
I think my next step will be to replace my home-made filament transformer (rewound MOT) with a commercial filament transformer, which I now have, and a small variac and voltmeter for filament voltage adjustment. It won't make my sparks any longer but it will be much more efficient. My MOT-based filament transformer draws about 750 watts! It gets quite warm even with a cooling fan. I measured the commercial filament transformer under load and it only draws about 120 watts and stays completely cool.
Steve
----- Original Message -----
From: "Chris Reeland" <chrisreeland@xxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Friday, March 16, 2018 3:30:07 PM
Subject: Re: [TCML] VTTC MOT question
Hi Steve,
Yes, I am back to my bigger copper tube toroid again. I have said in the
past recently that I always find myself going larger especially if pulsing.
I tried 4 other smaller sizes working back up to this. I have several more
going bigger, but of course they get too physically big for the size of
this coil, and then I would run into frequency problems again, which I want
to also say if you are considering larger, you may want to figure out if
you are going to have a possible frequency problem of pulling it too low.
This is why I rewound my secondary for a higher starting frequency. I have
alot more "headroom" to try various changes.
Yeah, having the feedback above a fairly tall primary can have some
problems. I have mentioned this also in the past. You got lucky you caught
is soon enough and have taken corrective action, I have seen variations of
what you said you did to prevent this.
Me, I have stopped a while ago of the "traditional" above the primary. I
always put it below now. Me, I feel (and some may disagree with me, which
is ok) that even though in theory, it is only supposed to be affected by
the primary, it seems to be affected by the higher voltage built up on the
secondary on the upper end, which happens when you have a taller primary.
If a short traditional primary, it is ok above.
At the bottom below the primary, you are of course located at the bottom of
the secondary, which is mostly current of course, and also has the benefit
of eliminating high voltage short arcs between the feedback and secondary.
I would also say this is much healthier for the grid wire of the tube to
eliminate this from happening.
I will have more details on this later, but I "was" peaking during the
pulses about 23+ amps at "140" 100% variac input.
I have not yet done any changes yet last night or today yet. Kind of taking
it easy...was tired from work. Going to mess around a bit later I think.
I should be able to give more details and comments and pictures this
weekend sometime.
Chris
Sent from my LG V20
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