Re: [TCML] Isolating Transformer

[dave pierson <dave_p@xxxxxxxxxxx>]

> My knowledge about electronics and frequency filters is limited to
> basic stuff, so is it valid if I'm wondering if an off-the-shelf
> line filter does do anything usefull in the first place?
  it varies.  depends on the filter.

> Especially for larger coils with a resonant frequency around or below
> the 100kHz, since I think most filters start to be effective from the low
> Mhz range. Doesn't anyone happen know usefull schematics for a DIY high
> current, low-pass filter, which has an effective cutoff above mains
> frequency?

> As far as I've learned, an iron core in a transformer, is effective at
> mains -low- frequencies and therefore shouldn't pass the higher
> frequencies.
  Sort of: Transformers, as all components, have lots of
  stray effects.  Notably, in this case, there is stray capacitance
  primary-secondary, primary-core-secondary.  This stray capcitance
  can pass higher freqs nicely.  Special transformers, as i mentioned
  earlier have internal shields.

  Another stray effect: highish freqs can radiate AROUND a filter,
  coupling coil side to line side by capacitance, inductance, emi.
  to be Really Effective the filter must be 'in' a 'shield wall',
  aka a Faraday Cage. 

> But I've read higher frequencies are still passed, because of
> inductive coupling between windings, which leaves me a bit confused.
  And capacitive.  There are the ideal components, existing in
  textooks, and the real ones, with lotsa stray effects.

>A bit of explanation would shed some light on this matter.
  bESIDES A BIT OF tESLA coil tinkering, i have worked in
  pro grade EMI/RFI.  One of my 'mentors' learnt his on
  1500VDC, 2000A locomotives...

  best
   dwp
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