Building a Successful Tesla Coil: Tips and Tricks for Coil Builders

[EvilTesla]

Tesla Coils!

How many here have built Tesla Coils?

I am wondering becouse i am currently building my seconed Tesla Coil.

(My first one barly worked, pretty much made out of hot-glue)


And I'd like some group to dump all my questions on, only other forums I know of to post questions, won't answer most of my Endless questions.



So, is anyone else here besides me coil?

 

[berkeman]

The search feature is your friend. I did a thread title search on Tesla, just in the EE forum, and got these hits. Hopefully those threads will answer most of your questions:

https://www.physicsforums.com/search.php?searchid=1352131

Welcome to the PF, BTW.

 

[noumed]

with a name like EvilTesla, maybe it's a bad idea to divulge him all of our information... he's on to something with those coils...

 

[EvilTesla]

lol, I promise I won't do anything overtly evil without at least a small warning and a one-liner.

I have looked through the first few pages of results and found nothing helpfull.

I guess I'll just ask my first two questions and see what turns up...

First, when building the capacitor, I know the plates have to be smaller than the dielectric to avoid flash-over, but how much smaller? would a .5 inch boarder do it?

Second, if I create a capacitor with ten layers of a 4 mill material, can I assume that the total highth is 40 mill? Or is it significantly greater due to some error?


I do have more questions (they never end) these are just the simpilest so far...

 

[kashish0711]

What material did you use to make it?

If you use a normal beer bottle, you will be able to make a good enough capacitor :)

 

[RayRoc]

Have made many of them, including practical 50,000V air core resonant capacitor charging power supply.

as to your questions, flash over spacing:
it depends on your primary voltage, air breaks down at 70,000V per inch (under controlled circumstances) but because homemade capacitors don’t control corona discharge this distance is much greater. I suggest that you experiment. Also the primary circuit can have much higher voltages then the primary transformer actually provides I would design the capacitor at least 4 times as resistant to the voltage then what your transformer will give you. That said, for 12,000VAC I usually go with 1" of space around the plate (not submerged in oil). Note that 12,000VAC has a peek to peek of around 16000V

As far as the plate stack, yes you can assume that it will be 40 mil, if you build a clamping device, if you just stack it, it will be taller. either way you will want to measure it as the calculations depend on it. You can clamp it with wood and 3/8" plastic all thread. or nylon with plastic all thread.

Most PE film I have used resists voltages of 1500V/mil minimum. It varies greatly. I might make a test jig. I assume that you are using a neon sign transformer. You should have an autotransformer supplying the power to the system so you can adjust it, If you don’t have one I suggest getting one. Anyway to setup the jig you simply get two blocks of dry wood, put some aluminum foil tape on the two blocks, put the sheet between the plates and connect the plates to the neon sign transformer. Use the autotransformer to bring the neon sign transformer online, turn the dial up slowly, and note when the dielectric breaks down. Do this several times and use the lowest value that you tested to.(unless it was a defect in the PE film).

I might use a 40 mil thickness to make a 12000VAC Polyethylene capacitor but that is just me not pushing the limit. at 10 layers, you should have enough redundancy to avoid failure due to small film defects.

Be safe.

 

[RayRoc]

one more thing, corona discharge is destructive to the PE dielectric, it will destroy your capacitor if not built with plenty of extra bulk. although you don't have to worry much below 4000V, 12000V produces plenty of it.