Need help figuring out whats wrong with my tesla coil

Thread Starter

johnboyman

Joined Jun 1, 2019
39
Hello. I am building a tesla coil for many different reasons. I have read about them for a long time so i finally decided that i have to build one. I am pretty sure i know most important things about them. This is the system I have put together. It has a Terry filter that is shown in one of my image uploads. Then after that there is a pole pig neon sign transformer at 15000 volts and has a 100 mA fuse on it. Here are the specifications of my capacitors and inductor.

-Inductance (L): 17 uH
-Capacitance (C): 0.023 uF
-Resonant Frequency(F): 254.201 KHz

Inductor:
-Diameter (D): 6.5 inches
-Number of Turns(N): 12
-WireDiameter (W): 0.25
-Turn Spacing(S): 0.25

Capacitors are: .33 uF each

Height: 7.5 inches
Length Of Wire: 282.743
Inductance: 17 uH
.33uF/13 = 0.025 uF

2000 Volts each * 12 = 25,000 Volts

I used http://deepfriedneon.com to calculate the inductor and the capacitors properly. My spark gap is a rotary spark gap and works well.
I have hooked up my capacitors and spark gap in series and it will run well. I can leave it running for 5 minutes without problems. When i wire it like a proper tesla coil and add the inductor into the circuit it will blow the 100 mA fuse but not any other fuses like the wall fuse. The transformer hums very loud. Once i hooked up a randomly made inductor and hooked it up to a small ac powersource and the transformer hummed in a similar way. I have worked on this for a long time and cant figure out what the problem with it is I cannot stop now, so I am looking for some help thanks for any tips.
 

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MisterBill2

Joined Jan 23, 2018
6,998
I believe that the circuit shown is incorrect. The capacitor needs to be connected across the primary coil and the spark gap needs to be in series with the high voltage source. The transformer loud hum is because of the large overload current. So a first thing to try is having the correct connections.
 

Delta prime

Joined Nov 15, 2019
487
Hello there:)
I believe that the circuit shown is incorrect. The capacitor needs to be connected across the primary coil and the spark gap needs to be in series with the high voltage source
That is exactly how it looks.Butt
As soon as the voltages of the spark gap adjusted according to the peak voltage of the capacitor are equalized, a short circuit occurs between the spark gaps. And, the primary coil with the capacitor becomes the parallel circuit. Tank circuit. :)
The primary coil and the main tank capacitor form the primary resonant (LC) circuit. For proper operation, a Tesla Coil must have identical primary and secondary resonant frequencies.
Therefore, building a tesla coil should not be done by people who have insufficient technical knowledge.:)
 

MisterBill2

Joined Jan 23, 2018
6,998
Except that the capacitor needs to be connected across the Tesla coil primary in order totune it to resonance. That way the circuit can continue to oscillate when the arc stops conducting.
 

Delta prime

Joined Nov 15, 2019
487
:) The spark gap fires and transfers energy from the tank cap to the primary coil every half-cycle of the mains supply (e.g. 100 times a second for a European 50Hz supply). This means that the transformer only has the time in one half-cycle (10mS) to recharge the capacitor for the next firing of the gap. A capacitor that is only charged up to half its capacity in the time allowed is not being used fully, and a small cap which could be charged twice over in the time is missing out on half the power available.:)
 

thedoc8

Joined Nov 28, 2012
148
View attachment 216515
Hello thanks I found an alternative circuit design is this the one that you are talking about? I will give it a try hopefully that the answer. Thanks again
This picture is correct the other picture will work also, but this is the picture you want to use. Lot less stress on the transformer using this setup. But that is not what is making it blow the fuse, where is the fuse you are talking about, I seen none in the pictures. Also where is your secondary, don't see it in your pictures. The cap in series with the primary is now the preferred method as this pictures showes.
 
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Thread Starter

johnboyman

Joined Jun 1, 2019
39
This picture is correct the other picture will work also, but this is the picture you want to use. Lot less stress on the transformer using this setup. But that is not what is making it blow the fuse, where is the fuse you are talking about, I seen none in the pictures. Also where is your secondary, don't see it in your pictures. The cap in series with the primary is now the preferred method as this pictures showes.
Hey thanks for the tips. I have not tried running it with the secondary Because I just wanted to get it running indoors first without and streamers. Do tesla coils require a secondary to run. I have a perfect secondary 252 hz the math is correct for the LC circuit. The fuse is at the top left hand size hanging off the side bin.
 

MisterBill2

Joined Jan 23, 2018
6,998
Without the secondary it is not a Tesla Coil. The resonant primary and resonant secondary are the whole thing. The power transfer is what it is all about. Presently there is a lot of incorrect stuff published that does tend to be confusing.
 
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