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EMI filter?

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LAN_403

CT2

Mon Apr 30 2007, 07:31PM

Registered Member #180 Joined: Thu Feb 16 2006, 02:12AM
Location: Ontario, Canada
Posts: 187

To connect it, it goes like this: There are three connections in and three connections out. There will be two for the 110VAC in (neutral and live) and then one for ground. On the other side there will be two for 110VAC out (live and neutral) and a ground connection. It just goes in series with the power to your coil.

Firnagzen

Tue May 01 2007, 04:11AM

Registered Member #567 Joined: Tue Mar 06 2007, 10:55AM
Location: Singapore
Posts: 147

But, direct quote from HVWiki http://wiki.4hv.org/index.php/Solid_State_Tesla_Coil (All the way to the bottom.) :

RF ground
...is directed just like any other tesla coil. Directly to mother earth or through an EMI filter to the power line's ground.

My understanding from this is that there is some way of using the EMI filter and the mains ground to totally eliminate the need for an RF ground at all. Is my understanding right, or does the wiki need a fix? And if my understanding is right, how?

CT2

Tue May 01 2007, 04:31AM

Registered Member #180 Joined: Thu Feb 16 2006, 02:12AM
Location: Ontario, Canada
Posts: 187

The EMI filter's ground is just the same ground as your house ground. This is because you hook up the ground to the green wire (ground) of your house wiring. The filter is suposed to stop interference from getting through it and into/out of what ever you have it hooked up to. You can hook a tesla coils secondary RF ground to your house's ground, or through a filter to the houses ground, doesn't matter because I'm pretty sure the filter only filters the line voltage and not the ground wire. But some people recommend against hooking up your tesla coils RF ground to your house' ground, I personally havent had any problems with doing that but my coils are small...

ragnar

Tue May 01 2007, 05:03AM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

Grounding the secondary to mains ground can be dangerous for a number of reasons:

If the ground isn't as low-impedance as it should be (reactive or just resistive), then devices connected to ground can float to high voltages.

Mains ground wires aren't made for carrying high-frequency RF currents. They'll get hot, and you can set the insulation on fire deep inside your walls. Maybe you can get away with it for small coils... but there's no guarantee. That's why I use a copper sheet as a floating counterpoise.

...

Tue May 01 2007, 05:19AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

I should also point out that in that schematic of a line filter the grounds are drawn a little funny, all of the grounds must be connected together (not floating between a few caps) or you run a rick of a 'hot' chassis.

Firnagzen

Tue May 01 2007, 05:37AM

Registered Member #567 Joined: Tue Mar 06 2007, 10:55AM
Location: Singapore
Posts: 147

Dang, and I was hoping that using a EMI filter would solve all the problems associated with grounding a tesla coil to a mains ground. Oh, well...

One last thing, though, what's a floating counterpoise? (Blackplasma mentioned this in his post.)

...

Tue May 01 2007, 01:36PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

A counterpoise is just a large sheet of metal (preferably copper/aluminum) that you use as the ground. Because there is only an AC current, and it is at a very high frequency, the counterpoise acts like a capacitor in series with ground, and likewise the coil thinks it is grounded :)

Firnagzen

Wed May 02 2007, 09:54AM

Registered Member #567 Joined: Tue Mar 06 2007, 10:55AM
Location: Singapore
Posts: 147

Oh, I see. But I live in a high rise flat (Well, third floor, but you get the idea.), will a counterpoise still work? It'd be relative to the third floor, well, floor!

uzzors2k

Wed May 02 2007, 10:15AM

Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308

Yepp. The counterpoise acts as a ground, so you don't need a real earth ground. It doesn't matter where you are.

Dr. Shark

Wed May 02 2007, 12:26PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

Whoa, this is getting confusing! The original question was about grounding the SECONDARY coil, the later post all address the PRIMARY side of the Tesla coil.

The filter from the first schematic is not "funny" but rather common practice with Class II devices like laptop PSUs which have two-prong plugs and no physical ground connection. They derive their ground through the so-called Y-capacitors from the AC mains. The point of this practice is exactly what we are trying to achieve here: Keeping noise out of the mains ground.

I don't know if connecting a Tesla Coil there would be a major safety hazard, so I'd like to hear a qualified comment on this.

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