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Re: EMI Filters



Original poster: Karl Lindheimer <karl@xxxxxxxxxxxxxxx>

Paul,

The EMI filter that you have most probably "recycled" for your experiment was initially chosen to either protect the product from line-noise, or prevent any EMI from the device from back-feeding to the A/C line. It consists of an LC/RC circuit designed for a specific set of frequencies. Your ignition coil and/or flyback, or Tesla Coil devices may simply overwhelm the filter with their massive EMI/RFI outputs. The simple way to protect valuable equipment is to have the devices plugged into a surge strip, and simply switch the strip off when performing experiments. Before I followed my own advice, I "blew" out a GFI outlet 300 feet away connected to a separate equipment ground. Also, you may have luck using "Ferrite" beads on the suspect conductors to reduce some of the hash.

Karl

On May 6, 2005, at 4:38 PM, Tesla list wrote:

Original poster: "Paul B. Brodie" <pbbrodie@xxxxxxxxxxxxx>

Karl,
I'm, sorry, my hands were typing before my mind was functioning! The EMI filter is wired between the variac output and the coil driver. The volt meter is "behind" the EMI filter along with my house wiring. Now I'm concerned about running my Tesla Coil from my house supply as I have a ton of sensitive computer equipment in the house. I do have a separate RF ground outside. It is an 8 ft. ground rod in the ground just outside of the garage. I have another 20A EMI filter and I think I will wire it in between the wall outlet and the variac so that I have 2 EMI filters with the variac in between them.
Paul
Think Positive


----- Original Message -----
From: "Tesla list" <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx>
To: <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx>
Sent: Friday, May 06, 2005 2:18 PM
Subject: Re: EMI Filters

> Original poster: Karl Lindheimer <<mailto:karl@xxxxxxxxxxxxxxx>karl@xxxxxxxxxxxxxxx>
>
> Hi Paul,
>
> If I understand correctly, you state that the EMI filter is between the
> wall outlet and the variac? If that is the case, the filter will only
> reduce any back EMI from reaching the wall outlet and the rest of the
> connected house wiring on the same circuit. The variac and meter are still
> exposed to the EMI from the coil. My flyback transformer experiments also
> created huge RF/EMI necessitating that I disconnect any valuable/sensitive
> equipment from the AC line. I ended up building a robust simple power
> supply to spare my lab grade bench supply.
>
> Karl
>
> On May 5, 2005, at 1:20 PM, Tesla list wrote:
>
>>I have a 20A EMI filter wired in reverse between the wall outlet and my
>>variac. I have a volt meter attached to the variac outlet.
>>
>>I was driving one of my ignition coils with a 600 watt dimmer in series
>>with a 2mF cap. As I powered up the variac, I could read the voltage
>>increasing on the volt meter all the way up to 120V. When I turned up the
>>dimmer, the voltage indication on the volt meter went haywire when the
>>coil began sparking. If I drew the ground away from the HV output, the
>>volt meter would stabilize as soon as the sparks stopped.
>>
>>What have I missed here? This isn't normal, is it??!! Could the EMI filter
>>be bad?
>>Paul
>>Think Positive
>
>
>