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Glad to hear that getting the system in tune helped resolve the problem. I had made the assumption that the system was already in tune and that you were still seeing these problems. Please let us know your results under full power. Best regards, Bert --Previous Message--
: Hi Bert,
: sorry for the first response,Iīve pressed the enter button.
: Your questions: 1.I use 12gauge stranded wire black called H07-VK.
: The closewound section is 33,46" tall,
: the spacewound 4".(one wire diameter each turn)
: The distance Topload C2 to last turnis also 4"
: 2.The distance betwenn L1 and L2 0,5" (around L1 0,39"
: air,because
: the heigh of L1 is adjustable and the frame for the first primary
: have to be 0,39".
: The Mylar is closewound to the edges of the arcrylic frame with turns.
: The distance between each arcylic rod/stick is 4,5".Where the wire
: isnīt
: supported is a air gap of around 0,2".
: 3.The mylar is mounted by plastic bolts direct on the top and bottom
: wooden plate.Here isnīt a gap.The bottom side of the mylar is 1,5"
: longer,because of the safe distance to the prim.coil.
: Iīve now made a few tests and have tuned the system carefully.
: 7,2turns seems to be the best.The system donīt arcs over and
: I can make the gap of the Topload of L3 27" and I get discharges
: without
: racing arcs on L2.
: The negative side of this experiments: Like Tesla I have a problem with
: horses,one horse has jumped over the fence.
: By this experiments I used a film camera,which is a little confused now.
: The camera stood 30ft away.
: Tomorrow I will interrupt my experiments for a little while.
: best regards
: alex
: --Previous Message--
: --Previous Message--
: Hi Bert,
: A time ago I posted a few messages/questions about magnifiers.
: Now the magnifier is already build.It looks very cool and Iīve designed
: it with magsim,inca,optmag and mandk.
: The driver has a diameter of 31,7" and is 40" high.
: There are around 250turns of 12gauge. The last 15 turns are spaced.
: The driver construction was very difficult,because the wooden varnished
: main frame.(there are no nails,screws;only wooden sticks and wood glue)
: The turns lay on a frame,consists of 22 (1,18" wide) arcrylic rods.
: The complete driver is packed in three layers (each 0,0315")clear PET
: (mylar?) plastics.Iīve made a isolation test with this plastic,and I
: couldnīt see those carbon tracks like Bert Pool.
: The primary is a flat coil with 2,36" wide copper ribbon.
: Distance prim.sec is only 0,4-0,5" because the wanted highest
: coupling.
: A coupling test at lowest prim. position gives k12=0,41
: The teritary has a diameter of 12" and has a turn length of 62"
: (1075turns)
: Topload C3: main toroid 59"x12,2"
: lower toroid 29"x6,7"
: Iīve made a few low power tests with
: around 3-4kVA and 10kV with static gap.
: Results: Around 16" stremers from breakoutpoint C3 and than
: racing sparks on L2 from top turns to the lowest turns.
: I called they racing sparks,but i donīt know what it is.
: They arenīt very bright.
: Iīve than arced the transmissionline to a grounded metal rod.
: If I have a distance to the rod less than 8" the racing sparks
: disappear.And the transmissionline arecd to ground.
: The problem is the daylight,so i couldīnt see where they comes from.
: They donīt arc to the primary,but between turns and plastic downwards,
: one time upwardsfrom the lower turns to the middle.
: Iīve made photos which I can post you,but because the daylight you
: couldnīt see a spark/streamer.
: Iīve a photo postet to a coiler,which has uploaded it to his internet
: site.
: The sphere on this photo is only for measurements and is now displaced
: (now 33"x5" toroid)
: best regards
: alex
:
:
: Hi Alex,
:
: Congratulations on first light - that's a very nice looking system! As
: you're discovering, insulation is one of the most challenging aspects of
: when trying to achieve tight magnifier driver coupling. Just about
: everyone who has built a magnifier has struggled with similar problems
: (usually L1:L2 flashovers). Sparking between the secondary and primary
: would be very hot, bright, and white. Since your sparks aren't bright,
: they do sound very much like racing sparks.
:
: As you are probably aware, the detailed mechanism underlying racing sparks
: is still not very well understood. In classical two-coil systems, racing
: sparks appear when the coupling is too high relative to the intrinsic
: dielectric strength of the secondary. The usual fixes are to reduce
: coupling or to reduce the topload breakout voltage (using a breakout
: point) to reduce overall voltage stress seen by the secondary. Changing
: the secondary's insulation system or increasing its length may also help,
: but these changes are not usually recommended since the other fixes are so
: much easier. Following are some questions, some thoughts, and some things
: you might try.
:
: 1. What type of wire/insulation are you using on L2 and what is the
: physical length of the closewound and spacewound sections of L2?
:
: 2. Is the space between L1 and L2 tightly filled by the rolled Mylar? BTW,
: PET is indeed the same thing as Mylar.
:
: 3. Is the Mylar tightly rolled on top of L2 or is there an air gap
: between?
:
: Some thoughts and some things you may wish to try: You appear to be
: exceeding the transient dielectric strength of L2's dielectric system.
: Adding a material with a relatively high dielectric constant (Mylar -
: k~3.3) in close proximity to your secondary winding can cause excessive
: electrical stress within any intervening air gap(s). If the resulting
: E-field is sufficient to produce corona in the gap then, in addition to
: possible corona damage of nearby polymers, you may encounter electrostatic
: effects due to corona charging of nearby dielectric surfaces. Nearby solid
: dielectrics that are "sprayed" by corona will develop localized
: regions of stranded surface charge. The better the dielectric material,
: the higher the localized potential and the longer these charged regions
: persist.
:
: During normal operation, subsequent voltage reversals on the secondary can
: further increase E-field stresses between the secondary and these nearby
: charged regions to the point where a surface spark can develop along the
: surface of the dielectric. This is sometimes called a guided spark. For a
: given voltage stress guided sparks propagating along a dielectric surface
: can be 3-5X longer than the distance in free air... and sometimes
: considerably longer. The surface spark is merely discharging excess
: stranded charge between regions of the dielectric, or between the
: dielectric and the winding. However, although they are initially
: electrostatic discharges, they may initiate followthrough RF discharges
: between portions of the secondary winding. Since these are lower energy
: sparks, they are relatively dim but they can cause progressive damage to
: your secondary and Mylar insulation.
:
: If you can prevent L1:L2 flashovers, the natural E=field grading across
: the single layer L2 winding and the E-field shielding from L2's toroid may
: be sufficient to prevent overvolting of the coil without the need for
: supplemental insulation. I suspect the root of your particular problem is
: the close presence of the Mylar insulation layer over L2. Unfortunately,
: it may be difficult to eliminate the insulation layer with your existing
: driver design.
:
: Some things you might want to try: 1. Try running the system in the dark
: to see if you are developing any corona on/across L2, especially
: underneath the Mylar. Also look for any consistent points where discharges
: seem to repeat and any possible anomalies.
:
: 2. Increase the gap between the primary and secondary and eliminate the
: Mylar layer. Elevate L1 versus L2 (if necessary) to increase coupling to
: the desired level
:
: 3. If you need to provide supplemental L1:L2 insulation, try using layers
: of LDPE film or thin LDPE sheet material. LDPE's lower dielectric constant
: (k ~ 2.3) should also help to reduce E-field stressses within any air gap.
:
: 4. If changing the insulation system still doesn't fix the problem your
: compact primary design may, in fact, be introducing excessive transient
: stresses on the lower portion of the secondary (particularly during
: ringup). Most other successful magnifier designs have used helical
: primaries which may tend to more evenly bathe a larger portion of the
: secondary with primary flux. There has recently been some discussion of
: this (only educated speculation at this time) on the Pupman Tesla List.
: There is no clear evidence of this as yet. However, it would seem to make
: intuitive sense...
:
: Good luck and best regards,
:
: Bert
:
:
:
:
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