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Re: [TCML] Two phenomena...
Hi Gary
That makes sense to me.
I'm running 17uF now with this new motor, but I bet it's not enough power. Maybe time to switch permanently to a grinder motor or back to the propeller.
Joe
Sent from Joe's mobile phone.
On Jul 26, 2010, at 10:32 PM, Gary Lau <glau1024@xxxxxxxxx> wrote:
> Hi Joe,
>
> I agree with John about the possibility of your motor losing synchronous
> operation. I think you said your phase adjuster has a 2uF cap? I know that
> when I set my phase Variac to the far end I lose sync with my motor. Maybe
> with your cap so small, you need to set the Variac to the far end to achieve
> a useful phase delay? Moving to a biggger cap will allow you to operate at
> a less extreme Variac setting.
>
> For the primary arcing - it sounds like you looked at all of the obvious
> things. Perhaps if you could post some more photos of the primary,
> something will jump out at us?
>
> Regards, Gary Lau
> MA, USA
>
> On Mon, Jul 26, 2010 at 12:18 AM, Joe Mastroianni <joe@xxxxxxxxxxxxxx>wrote:
>
>> I managed to debug my rebuilt coil to the point I'm getting nice arcs.
>> 15/90 NST. 41.8nf cap. Primary is 17 turns of 1/4" refrigeration tubing
>> spaced 1/4" apart. Using an SRSG consisting of a 1/30hp synchronous motor
>> running at 1800rpm, a 7" G10 wheel, and eight 1/4" tungsten carbide
>> electrodes.
>>
>> Through painful trial and error (painful because I had to kneel on my
>> garage floor) I managed to tweak the timing on the SRSG so that the safeties
>> stopped going off. Though I wound up leaving it in 240bps mode. I figured
>> I only have 45 degrees of "play" instead of 90. Proved to be easier than
>> tweak the 120bps setup, 2 or 3 degrees at a time, then trying to figure out
>> if I had the turning straightened out correctly. Trying to separate each
>> problem and solve it in turn rather than trying to figure out how to fix 6
>> bad things happening at once.
>>
>> When I finally got to the point where the safety gaps weren't firing, I
>> still had 2 things going on.
>>
>> 1) arcing between turns of my primary
>>
>> Never had this problem before. Or if I did it was usually due to some
>> piece of dirt or spider's web falling onto the primary, or worse, having my
>> ground connection come free and the arc went between the bottom of the
>> secondary and the primary.
>>
>> This is none of those situations, and it does indeed seem to be happening
>> at the higher power levels.
>>
>> Now I am at the point of considering that the reason this is happening is
>> the fact I'm running at higher power levels than before. I tried cleaning
>> off the primary, dusting/vacumming. Deburring where ever I could find
>> anything that seemed like a burr. When all was said and done I still had
>> arcing from the connection point between the MMC and the innermost turn of
>> the primary.
>>
>> So, I had some g10 laying around, and also some polycarbonate scraps. I
>> positioned some of the G10 and polycarbonate between the offending region
>> and the secondary and other turns.
>>
>> Well, it flashed over anyway. And interesting: the flashover blew the
>> polycarbonate scrap clean off the primary. (this is a piece about 2" by 1/2"
>> by 1/2")
>>
>> Still trying to figure out how to stop the flashover. Any ideas would be
>> appreciated.
>>
>> Item #2, and perhaps weirder.
>>
>> At about 120V on the Variac the spark production is quite nice. No
>> flashover on the primary - BUT
>>
>> I started to notice a long-period (like 2-5 seconds) oscillation in the
>> sparks - diminishing and increasing. It seemed to me like some kind of
>> weird timing synchronization issue, and indeed, it does "go away" when I
>> adjust the Freau phase shifter - but then I get other problems. It seems
>> when I'm in the "sweet spot" for timing, I get this slow oscillation.
>>
>> Now, I was thinking as well it could have something to do with the
>> environs. I'm running the coil in the garage and the sparks are ending up
>> everywhere - like the wood studs, the aluminum garage door, the tracks, etc.
>> And when it arcs to something grounded, the arcs are brighter, and I can
>> feel the current draw in the variac. But this effect seems to be different
>> from the long period oscillation.
>>
>> Just wanted to know if anyone else has experienced the same thing.
>>
>> Cheers,
>>
>> Joe
>>
>>
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