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MMC where to buy

billybob

Active Member
Also quick question, how big is too big for the toroid? I have two 12 inch diameter steel dog bowls and 6 foot air duct. Resulting in 20 inch diameter / 4 inch height toroid. Is this to big for my 4.5 inch diameter secondary?
 

DerStrom8

Super Moderator
Also quick question, how big is too big for the toroid? I have two 12 inch diameter steel dog bowls and 6 foot air duct. Resulting in 20 inch diameter / 4 inch height toroid. Is this to big for my 4.5 inch diameter secondary?
Questions like this are best answered by simulations and experimentation. Build your coil in JavaTC and try a number of different values.
 

billybob

Active Member
So I’m working on the strike rail today, and I was going to attach four wooden boards so the strike ring would be about 6 inches above the primary. My question is would the primary cause the zinc plated mending braces to melt or would it effect the emf of the primary? Here is a picture of what I’m trying to do...
 

Attachments

billybob

Active Member
Or would this be better?
Probably less stable, but I’m not sure if it would help.
 

Attachments

DerStrom8

Super Moderator
From personal experience, I'm going to recommend avoiding metal fasteners altogether around the primary coil. It is, in reality, an induction heater as you seem to understand. I would suggest using wooden fasteners (dowels, wood glue) in this application.
 

billybob

Active Member
Oh never mind. Minimum is $500
 

billybob

Active Member
I am buying the caps today. Should I go with the Cornell Doublers 2000 volt or 3000 volt? Both 150nf
 

DerStrom8

Super Moderator
I am buying the caps today. Should I go with the Cornell Doublers 2000 volt or 3000 volt? Both 150nf
Presumably you are asking whether to go with the 940C or the 942C series? The 940C series (3kV) have a substantially lower current rating and are most likely not suitable for Tesla coil applications. Use the 942C series.

Also, bear in mind the voltage rating displayed (i.e. 2kV) is DC, not AC. The AC rating of these caps is only 500V, so that is the value you need to use when sizing your capacitor bank.
 

billybob

Active Member
Presumably you are asking whether to go with the 940C or the 942C series? The 940C series (3kV) have a substantially lower current rating and are most likely not suitable for Tesla coil applications. Use the 942C series.

Also, bear in mind the voltage rating displayed (i.e. 2kV) is DC, not AC. The AC rating of these caps is only 500V, so that is the value you need to use when sizing your capacitor bank.
Ok I’ll go with the 942C then. Well it’s a voltage multiplier pulsed DC so it‘s not as detrimental as a pure sine wave right? Everyone else I talked to who has made MOT Tesla coils have gone by the DC rating and double or triple it to the output power. Also that go way over my budget and be a little overkill. I’m getting 50 caps

Thanks you DerStrom.
 

DerStrom8

Super Moderator
Ok I’ll go with the 942C then. Well it’s a voltage multiplier pulsed DC so it‘s not as detrimental as a pure sine wave right? Everyone else I talked to who has made MOT Tesla coils have gone by the DC rating and double or triple it to the output power. Also that go way over my budget and be a little overkill. I’m getting 50 caps

Thanks you DerStrom.
The purpose of capacitors in a Tesla coil is to create a resonant circuit with the primary coil. The current which they will be seeing during operation is about as pure a sine wave as you'll get :p

Hopefully they will perform well, just be aware that MMCs often blow a cap here and there. That's one of the main reasons they were invented - to make it easy to change just one or two (relatively) cheap capacitors instead of having to replace a single, giant, expensive capacitor. 942Cs are fairly rugged, but don't be surprised if you lose a few.

P.S. Oh, and please, call me Matt!
 

billybob

Active Member
The purpose of capacitors in a Tesla coil is to create a resonant circuit with the primary coil. The current which they will be seeing during operation is about as pure a sine wave as you'll get :p

Hopefully they will perform well, just be aware that MMCs often blow a cap here and there. That's one of the main reasons they were invented - to make it easy to change just one or two (relatively) cheap capacitors instead of having to replace a single, giant, expensive capacitor. 942Cs are fairly rugged, but don't be surprised if you lose a few.

P.S. Oh, and please, call me Matt!
I just realized that after I sent it. A giant LC circuit is all it is. I have faith that these will hold up nicely and according to deepfriedneon I will only need 21 caps (I will do more for insurance) 65nf is what I am aiming for.

Thanks Matt. IT’S FINALLY GETTING THERE!

I’m super excited.
 
Last edited by a moderator:

billybob

Active Member
Um can someone fix the above post please?
 

DerStrom8

Super Moderator
Um can someone fix the above post please?
Fixed. Looks like you had two quote blocks, and accidentally posted your reply inside the second one :)
 

billybob

Active Member
Fixed. Looks like you had two quote blocks, and accidentally posted your reply inside the second one :)
Yup that’s what happened XD
 

billybob

Active Member
Is tti.com a reliable electronic distributor? Or should I pay the extra 40 dollars and go with mouser?
 

billybob

Active Member
Ok I bought 50 caps from tti.com it costed $260
 

DerStrom8

Super Moderator
TTI is trustworthy.
 

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