Re: EMI Filters

["Tesla list" <tesla@xxxxxxxxxx>]

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
> >
> >
> >