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Re: DRSSTC Additional questions



Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Skip,

Even though the output is pretty even with a miss-tuned primary, the primary current may be much higher. It is like the system resonates the primary current up until a certain power to the secondary is obtained. The primary current will be least when the tuning is correct.

If the primary was so miss-tuned that there was no transfer to the secondary, the primary current and voltage would just rise un-restrained until something blows up. So tuning might now be a matter of finding the least primary current point per given output.

Cheers,

        Terry


At 09:13 PM 9/22/2005, you wrote:
Hi all
Ok, the primary feedback using Steve's two coil system works great. New questions


1. The tuning of the system is much broader than any TC that I have ever built. There is little difference in spark length when adding or subtracting two or three turns to the primary. Is this typical of DRSSTCs? Per JAVATC the coupling is between .18 and .2. The resonant frequency seems to hold pretty steady at 285khz regardless of the turns in the primary.

2. Doubling the tank cap size definitely lowers the resonant frequency and the input current goes up dramatically but there is little effect on the spark length and the primary turns still seem to have minor effect on the spark length up to a certain point. Are others seeing the very broad tuning that I seem to be getting.

So far I am only inputting 60vac to the full wave dc bridge and spark length is approaching 12". The secondary is only 18.5" long. I am leery of increasing the input voltage until I understand this apparent broad tuning.
Any comments would be appreciated. Thanks Steve and everyone for the feedback help.
Skip