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Describing the Inverted Center Tapped Resonant Transformer

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  • Harvey D Norris
    Hi All, My name is Harvey D Norris and to start things off a breif history is in order. I am the Author of the Binary Resonant System with homepage at
    Message 1 of 1 , May 7, 2001
      Hi All, My name is Harvey D Norris and to start things off a breif
      history is in order. I am the Author of the Binary Resonant System
      with homepage at

      I am interested in tesla coils, and adapting this special arc gap to
      their operation. To describe this we must first consider the ordinary
      center tapped transformer, which will be dealt with a little better
      in the next post. The center pathway is shared by two 180 phases that
      produce a net cancellation of current on that path, provided the
      opposing sides of currents are equal. For the thing I am talking
      about, the inverse situation applies where one resonant tank circuit
      will be divided into two, with a center pathway shared by both
      reactive sides from opposite directions, leading to the observation
      that twice the current exists on that pathway than on the sides
      alone. It is therefore a figure 8 tank circuit, that no one but
      myself apparently is willing to work on. To make this into an arc gap
      one merely needs the opening at the center of the 8. This opening
      itself will procur a voltage rise, if the circuit is tuned to the
      source frequency. The problems of this application to a tesla coil is
      the fact that that circuit is not tuned to the source frequency, but
      rather the secondaries resonant frequency. It is good now to explore
      what Tesla himself invented, with some practical hints for a dual
      spiral binary resonant arc gap.

      The first record Of Tesla's high frequency coupled
      oscillatory circuit with an air cored transformer is
      to be found in patent 454622 of 23 June 1891 under the
      title "System of electric lighting". The oscillator
      converts low frequency currents into "currents of very
      high frequency and very high potential" which then
      supplies single terminal lamps. (from Aleksandar
      Marincic's CSN preface)
      The arc gap in this schematic is within the tank
      circuit, something later abandoned as the best method.
      On July 2,1899 Tesla notes the reasoning for this;
      In a schematic showing the break within the tank
      circuit he comments... "the scheme of connections has
      the disadvantage that the primary discharge current
      passes through the break hence, the resistance of the
      latter being large, the oscillations are quickly
      damped and there is besides a large current through
      the break which makes good operation of the latter
      difficult. To prolong oscillation in the primary and
      increase economy one of the schemes before considered
      may be resorted to." He then refers to the
      conventional approach of allowing the break to be
      shunted across the hv secondary outputs where he
      comments.. "in this arrangement the currents through
      the break device are much smaller and the oscillations
      started by the operation of the break device continue
      much longer."
      Tesla makes no comment concerning the idea of placing
      an inverse tank circuit on the other side of the break
      in the first example for a center tapped high
      frequency transformer. In that situation two (180
      phased)primaries would recieve their oscillations from
      a single arc gap. The problem of the arc containing
      the entirety of the currents is then circumvented by
      the pathway established along the sides of the newly
      configured figure 8 LC quantities.

      So here I am making some conceptual suggestions upon
      implementing the "third schematic arc gap" apparently
      neglected by Tesla as a possibility. This is described
      using dual identical spirals. The usual reply that
      this is already accomplished by a bipolar tank circuit
      does not take into account the fact that in the
      "third" schematic possibility there are two and not
      one capacities involved.
      I am still working to try a NST gap like that. Cant
      take that much longer.
      I have made some preliminary modeling ideas using the
      dual spirals available at Radio shack as their flat
      stranded 50 ft insulated for a mini-tesla coil
      primary. I'm trying mine in a bipolar application for
      a mini tesla coil one would suppose that length of the
      wire is is small in comparison on the smaller mini
      secondary, thus making the operation at a high
      frequency. Since the duration of that rf burst is then
      a very small time period,I am aiming for a very high
      bps rate which this system should permit. Here are
      some considerations of difference in tuning with a
      single arc, oscillating two primaries 180 out of phase
      as I have described as a Binary Resonant System,(BRS)
      1)Because magnetic agreement between the primaries is
      necessary for the maximum inductance, and the currents
      on the primaries themselves are 180 out of phase, and
      the further fact that the spirals themselves are not
      themselves bifilar with respect to each other: to make
      the fields in agreement means that opposite outer and
      inner coil connections to the repective opposite hv
      terminals is necessary. The inner and outer leads of
      the dual spirals that remain are in turn connected to
      capacities which connect in series with the opposite
      hv potential. This then consists of two oppositely
      phased series LC quantities in parallel which is the
      current limiting condition before gap firing.
      2) The arc gap is made from the connections at the
      midpoints of the 180 phased series LC quantities, or
      the ends of the inner and outer wire spirals that are
      not connected to the hv secondary. Thus upon arcing
      the resistance of the primary is on either side of the
      arc: the arc is not directly shunted to the hv ouput.
      3) The capacities on each side are NOT made from the
      resonant frequency calculated from that sides L
      quantity, but rather the quantity established by the
      needed capacity to resonate with both L quantities in
      mutual inductance where the primaries are in series to
      determine this new L(total). A C(total) is then
      matched to this new L figure to resonate, and each
      side will recieve twice C(total). This is because
      these capacities will appear in series when the gap
      fires, thus to arrive at C(total) twice the value must
      be used in series.
      4) Because of the dielectric qualities of the
      insulation between windings the spiral set also has a
      internal capacitance, and adding capacitance on each
      side of the LC quantites may not change the resonant
      frequency as suspected. Since the set then has a
      recorded C internal capctance of 220 pf, and a
      measured .636 mh L quantity correctly wired in series,
      a natural resonant frequency of 425,000 hz might be
      suspected. A scope measurement of this frequency seems
      to indicate 588,000 hz including the 25 pf scope
      5) It may be possible to simply connect the inner and
      outer spiral ends together at an arc gap and have the
      primary resonate at its own natural resonant frequency
      established by its internal parameters. Of course then
      one would have no tuning and be limited to placing the
      correct secondary to resonate in place.
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