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Center tap coil?
Posted by Russell on 3/5/2007, 7:11 pm Any ideas?
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Re: Center tap coil?
Posted by Russell on 3/6/2007, 5:42 am, in reply to "Center tap coil?" --Previous Message-- Thanks.You guessed it right.The top load ,ext..
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Re: Center tap coil?
Posted by Bert Hickman on 3/5/2007, 8:55 pm, in reply to "Center tap coil?" Hi Russell, As you may have guessed, your system is significantly out of tune. In fact, your primary circuit appears to be tuned to at least twice the frequency of your secondary. This "forces" your secondary to develop the highest voltage at its midpoint each time the primary gap fires. You didn't mention what size and type of topload you had on your secondary. Also, because of the long secondary winding and relatively small wire size, you have about 2000 turns on your secondary. This is on the high side and is contributing to your inability to properly tune your system. A toroid topload (if you're not already using one) should be made from 4" diameter aluminum dryer duct and a pair of pie pans to provide proper topload capacitance and protection for the top of your secondary. A toroid with an outer diameter of say 16 - 18" will work nicely. If you already use a toroid, please provide its dimensions. I also assume you are running off 60 Hz and using a static spark gap. I'll also assume that your 0.02 uF caps are connected with two groups of three series connected caps that are then connected in parallel so that you have an effective tank capacitor or about 0.013 uF at 48 kV. I'll also assume that you have a flat spiral primary. If this is wrong, please provide corrections. Given the above, you don't have a sufficient number of primary turns to bring your system into proper tune. In order to bring your system into tune, I'd recommend adding at least another 4-5 turns to the primary, and removing 8" of turns from the top of the secondary. This will reduce your secondary to about 1500 turns, and it will also raise its operating frequency. The combination of the added primary turns and reduced secondary turns should then allow you to bring your system into proper tune (at around primary turn 14 - 15). Note that this may be different if I have not used the proper assumptions for your primary tank capacitor. You may wish to use one of the many useful design programs that are out there (such as JavaTC) - this will allow you to accurately model your design ahead of time. You can find it here: Good luck and best wishes, Bert
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