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Re: Induction heating in toroid / short circuit of secondary
The current in the lower windings and uppermost windings of a resonance
transformer is considerably different. A much more powerful current exists
in the lower windings and is the reason why some of our designs use a much
larger gauge of wire in the lower 50-100 turns. The first 30-50 turns is
very critical with regard to efficient output. If we replace the larger
wire with smaller wire in the lowermost turns the output is less due to the
driving current being considerably less.
Hope to clear up any confusion on this matter.
Dr. Resonance
-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Sunday, December 26, 1999 7:26 PM
Subject: Re: Induction heating in toroid / short circuit of secondary
>Original Poster: Kennan C Herrick <kcha1-at-juno-dot-com>
>
>To Dale Hall, "rwall" and all:
>
>I'll repeat here my perhaps-pedantic comment on "ES" vs. "electric": "If
>you mean by ES, electro-static field, I don't think there is one:
>"static", after all, means "standing still". That is, a bunch of
>electrons just sitting there. Not so, in a t.c. But I'm sure you mean
>the more general <electric field."
>
>I'm sure we all mean "electric field": technically; in our case, an
>alternating electric field--alternating between + and - polarities
>(between deficiency of and surplus of electrons, respectively) at the
>frequency of the secondary's self-resonance. None of those electrons are
>standing still, of course; they are all rushing up & down in the
>secondary coil between earth and the top electrode--eventually to break
>out (or in!) in a spark. And any "static" electric field, e.g. in a Van
>de Graf machine, must, of course, at one time have been not-so-static,
>having increased from 0 to its present level over some duration of time.
>How quickly-varying a "static" field must be before someone starts to
>call it "dynamic" is anyone's guess. So much for quack-Dr. Herrick's
>explanation of electric fields.
>
>As to the magnitude of the magnetic field at the top of the coil, upon
>reflection I think it must be of much the same magnitude as at any other
>place along the coil. After all, current flows serially, so to speak,
>from one turn of the secondary to the next. If the secondary coil itself
>is a relatively poor radiator of EM energy, as is alleged, then much the
>same current must flow in the top turns as in the bottom ones (or at
>least, in those quite a bit further down). Thus much the same
>self-generated magnetic field must exist.
>
>If there is current flow within the loop of the toroid, then that current
>flow must be induced by a magnetic field. Significant current flow
>implies significant magnetic field impinging upon the toroid. From
>where?...certainly much more from the secondary than from the primary.
>
>I welcome correction, of course.
>
>I'll take this opportunity to relate a bit of insight--perhaps old-hat to
>some but perhaps useful, particularly to solid-state t.c.-ers. Up until
>recently, I have been at some pains to limit the duration of the
>pulse-bursts that excite my MOSFET-driven t.c.--to just a little longer
>in duration than the time necessary to create a spark (maybe 350 usec).
>That was so that I could keep the average input power down, allowing for
>more sparks/second before I pop a ckt breaker.
>
>I found, however, that the sparks were rather pallid (Do I hear, "Of
>course!"?) and subsequently I found that when, serendipitously and due to
>electric-field interference with my control circuit, the burst length
>increased to ~3 ms, I got nice, fat impressive sparks. So I am going to
>"sacrifice" spark rate for fatter sparks, and am currently working to
>stabilize my control circuit so that when I have a 3 ms burst length it
>is >I< who determine that and not stray fields.
>
>Also, it appears that there is some tradeoff to consider between
>achieving a high spark stand-off capability with a smooth/large-c.s.d
>toroid on the one hand and providing plenty of pulse-burst power
>available (a relatively large primary current) on the other hand. The
>high spark-standoff capability will tend to allow a relatively long spark
>to initially form. But it is the available "punch" of primary power that
>is going to "fill up" that initially-pallid spark with additional energy
>for an extended period of time, and likely at the same time extend its
>length. The latter, because the tip end of an existing spark
>constitutes an extremely "sharp point" from which it is relatively easy
>to squirt even more electrons if one has the power available to do so.
>
>I don't have a feel for any optimal relationship between large/smooth
>toroid and primary power. Help, anyone?
>
>--And thus a final comment: My recently-advertised "novel top electrode"
>might not be so much of an advantage--assuming it were to work as
>intended. It may be that a power-punch, so to speak, is more important
>in extending spark length than the maximizing of the initial voltage on
>the toroid.
>
>Ken Herrick
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