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Re: H&R transformers by the numbers



Subject: 
        Re: H&R transformers by the numbers
  Date: 
        Tue, 25 Mar 1997 08:52:23 -0500
  From: 
        "Thomas McGahee" <tom_mcgahee-at-sigmais-dot-com>
    To: 
        <tesla-at-pupman-dot-com>
    CC: 
        "Tesla-2" <tesla-2-at-emachine-dot-com>, <major-at-vicksburg-dot-com>



----------
> From: Tesla-2 <tesla-2-at-emachine-dot-com>
> To: tom_mcgahee-at-sigmais-dot-com
> Subject: H&R transformers by the numbers
> Date: Tuesday, March 25, 1997 12:08 AM
> 
> From: Roderick Maxwell <major-at-vicksburg-dot-com>
> Date: Mon, 24 Mar 1997 21:08:50 -0800
> Subject: H&R transformers by the numbers
> 
> Well I got those big suckers today! Now the only question is how do you
> connect them in antiparallel? Since all of the terminals are numbered
> can anyone describe the way you connected them? (By the numbers of
> course).I know which wires are which but I,ve never connected
> transformers in series or in antiparallel,only in parallel.
> 
> 
> 
> 
>                               Frankensteins Helper
>                                      Max
> 

Max,
Hope the stuff appended at the end of this post helps you determine the
wiring numbers for your particular transformer(s).

Once you have determined the  wiring of each transformer, you need to
wire
them together in an anti-parallel arrangement. That is just a fancy term
for winding the transformer primaries in such a way that they are
paralled,
but the phasing is reversed. That allows us to wire the secondaries in a
special series arrangement in which the outer HV leads produce opposite
polarities at any given instant. One reason for doing that is that it
allows us to ground the center tapped secondaries to the core and to AC
ground so that the electrical stresses on the transformer are reduced.
It
is important that it is the *INNER* HV leads that get tied together and
connected to ground!

Some stupid ASCII drawings:

A1----p s----C1
      p s
      p s
      p s
B1----p s----D1


A2----p s----C2
      p s
      p s
      p s
B2----p s----D2

Assume:
(p) is primary
(s) is secondary
A/B are primary wires
C/D are secondary wires
D1 and D2 are the inner HV
C1 and C2 are the outer HV

Wire the primary wires together as follows:
First AC input wire goes to A1 and B2.
Second AC input wire goes to B1 and A2.
That puts the primary in anti-parallel.

Wire the secondary wires as follows:
D1 connects to D2.
(That connects the inner HV wires together).
Ground the connection just made to the core.
Ground the core to the AC ground (Green wire on line cord).
(You MUST use a three wire line cord).

The C1 and D1 wires are now the HV output wires.

You *MUST* have a safety gap for EACH transformer. Adjust each gap for
breakdown at about 5KV. The safety gaps each connect to the core ground
(which connects to AC ground and the inner HV wires). The other side of
each safety gap goes to one of the outer HV leads. 


Fr. Tom McGahee

****** Appended Stuff

> Subject: Re: 10KV RMS -at- 300MA for less than $100
> Date: Saturday, March 22, 1997 2:23 PM
> 
> >             Tue, 18 Mar 1997 14:12:17 -0800
> >             Skip Greiner <sgreiner-at-wwnet-dot-com>
> >         To: Tesla List <tesla-at-pupman-dot-com>
> 
> ***SNIP***
> 
> > 
> > Hi Fr. McGahee and All
> > 
> > 
> > Today I received 2 of the infamous trannies from H&R. They appear to
> > have arrived in good shape. They do have the wire leads which is
> > apparently a plus. Good. They arrived without a wiring diagram. Can you
> > help? The terminals are marked 1 thru 7. 6 and 7 should be the HV leads
> > since they have the HV connector on them. 1 and 2 go to what I assume
is
> > the resonator winding which is totally separate from the second winding
> > which contains the HV winding. 3, 4 and 5 I assume are the primary
> > 115vac inputs. If all of the above is true, do you know how 3,4 and 5
> > are to be connected?
> 
> *** INCORRECT! PLEASE SEE BELOW! ***
> > 
> > Before I blow one of these up, there is one thing in the discussion so
> > far which I do not understand. What is the problem with running these
> > things in a TC application *with* the resonator cap connected? I'd
> > really appreciate some inputs on this.
> > 
> > Thanks in advance
> > 
> > Skip
> 
> Skip, Huffman, and others interested in the H&R transformers,
> At the end of this post I have appended the relevant portions of Barry
> Benson's latest response to my queries concerning his successful use of
the
> H&R transformer. Please read it in its entirety.
> 
> In the meantime I will attempt an appropriate response to Skip's
questions,
> and a few other questions that have been raised.
> 
> Different versions of this transformer have the wires *numbered somewhat
> differently*. For this reason I will refrain from talking about them by
> number, as that might lead to someone misunderstanding and assuming that
> the same numbers apply to their particular transformer. However, it is
easy
> in practice to figure out what each wire or terminal is, so that is what
we
> will do!
> 
> It appears that the C&H transformer is for all intents and purposes the
> same transformer as the H&R transformer (but the C&H costs a few bucks
> more).
> 
> 1) The High Voltage Secondary is the largest winding on the transformer.
It
> has two connections. If you have the wire-lead style transformer, then
you
> will find two Black High Voltage Silicone wires that have a breakdown
> rating of 20KV marked on them. If you have the quick-connect style
> transformer, then the terminals are mounted about 1.5" apart. (This close
> spacing is the real weak point of the H&R transformers. The ones with
wire
> leads are less prone to arc-over in Tesla coil use). 
> 
> Examination of the wire used in the secondary shows it to be #28 gauge,
> which is excellent. HV insulation is impregnated paper between winding
> layers, and cloth tape that has been heavily varnished as a protective
> outer covering. This appears to be more than adequate. The weak spot, as
> already noted, is the spacing between the inner and outer HV leads in the
> case of the quick-connect variety. If you have the quick-connect variety
> you can modify it *without* disassembling the whole transformer.
> 
> 
> 2) The secondary is physically wound over the Resonating Winding. This
> winding is center-tapped. In the wire-lead style transformer, these wires
> are red. In the quick-connect style the three terminals are located on
the
> side of the transformer opposite the HV connections. 
> 
> Barry mentions that he does *NOT* use the Resonating Windings at all. I
> have experimented with using them, and have come to the conclusion that
it
> is best NOT to use them. When used, the *open circuit* voltage increases
> from 2,700 volts to 5,000 volts. But in Tesla coil use this leads to an
> undesireable charging pattern that shows itself as a sort of thumping
noise
> (the noise is generated in my system by the vibrations of the capacitor
> plates. The noise is merely an indicator of the uneven charging pattern).
I
> agree with Barry that we do well to just leave the Resonating Windings
> alone.
> 
> Yeah, well, OK, but for the curious among you, The open circuit voltage
> produced (according to *my* meter) is 2,700 volts with *NO* capacitance
> used. Applying the supplied 12 MFD -at- 600 VAC oil-filled cap to the two
> outside Resonating Winding Terminals resulted in a reading of 5,200
volts.
> Using the center-tap and either outside lead resulted in an output of
3,300
> volts. The wire used for the Resonating Winding is positively wimpy
> compared to the actual primary. Do *NOT* attempt to run the transformer
> using the Resonating Winding(s) as the primary! The current drawn through
> the Resonating Winding would exceed the current carrying capacity of the
> wire!
> 
> PLEASE, don't go trying to run this thing in resonant mode on your Tesla
> coil. Not only would it be a bumpy ride, but you may destroy the
> transformer.
> 
> 3) The Primary is the totally separate winding that looks like a pancake.
> It is wound with heavy-duty wire and held together with varnish. On the
> quick-connect version you can see the wire. It is quite robust!
> 
> Between the primary and the secondary there are two current-limiting 
> shunts. Removal of these shunts is not adviseable, as then you would have
> to provide external current limiting.
> 
> Some people have remarked that they tried to use these things for tube
> Tesla coils and found them unsatisfactory. If using the resonant
windings,
> I am *sure* they were lousey! They probably jumped all over the place
> voltage-wise! If used without the resonant windings then they should be
OK.
> By the way, if I were to use these to run tube Tesla coils, I would
> probably want to remove the shunts.
> 
> ***** Some additional comments *****
> 
> Safety gaps across *each* transformer are a must. If you have the
> quick-connect style transformer, please modify it, or it may not survive.
> Properly modified and protected, the transformers are excellent.
> 
> Yes, at 2.7KV RMS the voltage is a bit on the low side. However, the
> current capacity is large, and I have found that two of these delivering
> 5.4KV at 300 ma can do an excellent job in Tesla coil service. I had to
> change to a .05 mfd capacitor to get everything matched, and I am going
to
> have to fabricate a new spark gap for this sucker, but it is already
> producing better output than I used to get with a 15KV 60 ma transformer.
> As a consolation prize, we all get to use capacitors with lower voltage
> ratings if we want to. 
> 
> *** Barry Benson's Latest Reply ***
> 
> Fellow coilers,
> I finally got a second reply from Barry Benson on Chip's Tesla list
> regarding some of the questions about using the H&R transformers. I am
> reposting it to the Tesla-2 list since some Tesla-2 members may not be
> Tesla list members. For the sake of brevity I have cut out all but the
> relevant response material. Hope this proves useful. 
> 
> 
> Fr. Tom McGahee
> 
> >         Fri, 21 Mar 1997 12:04:00 -0500 (EST)
> >   From: 
> >         Benson_Barry%PAX5-at-mr.nawcad.navy.mil
> > 
> > Benson_Barry%PAX5-at-mr.nawcad.navy.mil
> > 
> 
> *** Barry replied as follows: ***
> 
> > 1) Do you use the resonating winding at all? The capacitor?
> > 
> > Never used it.  Never found a need.  I figured that since the
> > transformer had enough voltage from TC kickback to arc over
> > itself that it might be dangerous to try.
> > 
> > 2) Did you make *any* modifications at all to the transformer itself,
> > such
> > as removing the shunts? If so, could you explain what you did and how
> > you
> > did it? What were the practical results? Any "gotchas"?
> > 
> > Never touched it except for repositioning and putting some teflon
> > spaghetti tubing on the HV leadout wire. I mentioned this mod
> > a while back on the list.  If past posts could be organized for
> > encyclopaedic perusal it would save a lot of people from the
> > past mistakes of others such as myself.
> > The transformers that I purchased 10 years ago had an E core with
> > a flat plate on the E.  No shunts.
> > I wouldn't remove the shunts on the new ones without external current
> > limiting.  It might make it more efficient but at the expense of the
> > wire melting from the huge current these things put out.
> > 
> > 3) You mentioned repairing one of the transformers. What is the quality
> > of
> > their original construction in your opinion? Do you remember
> > approximately
> > what size wire was used for the secondary? Can they really handle the
> > rated
> > 300 ma continuously in your opinion?
> > 
> > It appears to have (polyurethane?) impregnated paper between the
> > windings.  It burns very fast.  Not the best insulation.  Mine are
still 
> > good
> > though after 10 years of use.
> > 
> > 4) Of the failure modes you have experienced, what were they, and how
> > can
> > they be reduced?
> > 
> > Arc over incinerates the insulation.  I protect mine with 1/8" needle
> > sharp
> > tungsten points set to break over at about 9 kV.  Every couple of hours
> > they have to be resharpened because of the current.

ADDENDUM-----------------------------------------------------
That is 2 separate
safety gaps (set to break at 4.5kv each-approx. 100v on variac) with
one side grounded to the inner high voltage leads of the transformers
which
are in turn grounded to the case (core) which is grounded to the 115
VAC ground from the line cord.
----- END ADDENDUM--------------------

>> I have thought of
> > using a horn gap for future tests because of the high currents.  Maybe
> > someone can try that out.
> > 

Note: A Horn Gap is sort of like a mini Jacob's ladder. The bottom of
the
gap is set to fire at 4.5KV, but then the gap material bends away from
the
starting gap. When an arc develops at the bottom of the gap, the hot air
rising makes the arc rise. Since the gap now diverges and gets further
apart, the arc will eventually extinguish. Without this feature the
safety
gap might continue to flame for an excessive amount of time after an arc
is
initiated.

Keep in mind that these transformers produce fairly high currents, and
the
arcs can be quite massive once they initiate. Make sure that the safety
gap
eventually turns off!

> > 5) Have you added any auxiliary stuff such as external current
limiting?
> > If
> > so, be as explicit as you can as to what you have added, and why.
> > 
> > I originally tried the two variac method.  One variac to adjust voltage
> > and one in series to adjust the current.  The current limiting variac
> > didn't because it didn't have the slice out of it as Richard Hull
> > pointed out in one of his earlier tapes.  As soon as the core saturated
> > the breaker poped.  I just run the system above that point.
> > I also have MOVS across the primary of both transformers.
> > One between hot and neutral, one between hot and ground, and one
> > between neutral and ground.
> > 
> 
> *** Note: the newer transformers have built-in current limiting at 300 ma
> and do not require any external current limiting ***
> 
> > 6) The common mode choke you mentioned: is this homemade, or can we buy
> > one
> > somewhere? Details?
> > Noise.
> > Homemade.  Use an old transformer core with about 1" square cross
> > section.  My core isn't gapped.  Strip the braid off of a couple
hundred
> > feet of RG58 solid polyethylene (A/U maybe) cable (fun!).  Wind about
50
> > to 100 turns around each transformer core leg.  One winding is
connected
> > in series with the output lead of one H&R transformer.  The other
> > winding
> > is connected in series with the output lead from the other H&R
> > transformer.
> > The ends of these windings go to the Tesla coil rotary gap.  The sense
> > of the winding connections is such that the current flow through one
> > winding
> > cancels the current flow through the other i.e. "common mode".
> > The whole choke is floated electrically by placing it on a 1/8" sheet
> > of plexiglas with 3" margins.
> > Any current surge that tries to feed into both high voltage leads
> > in the same direction at the same time creates magnetic fields that
> > add.  This makes the common mode choke appear as a very high reactive
> > impedance to Tesla coil noise "common" in phase to each line.
> > That is how an electrical engineer friend of mine explained it to me.
> > He said that the same kind of common mode choke is used in switching
> > converters for light weight power supplies to filter niose out of the
DC
> > output.
> > 
> 
> *** Since the purpose of this choke is to remove noise, it appears to be
> purely optional ***
> 
> > Current limiting.
> > He also said that if the windings were in the same direction then the
> > current from the transformers could be limited depending upon the
> > number of turns and size of the core (> saturation).  He said that the
> > much smaller current out of the high voltage side of the transformers
> > would be a lot easier to limit this way than with variacs and arc
> > welders
> > on the multiampere primary side.  I've always been intrigued by this
but
> > never tried it.  I will try it on my 10 kw next system.
> > 
> > Cleaning.
> > I would recommend dusting off your transformer coils before a run to
> > prevent an accident from arc over due to invertebrates and dust.
> > 
> 
> *** Yes, Dead Bug Removal is a must when using open frame transformers
that
> are not in any protective enclosures. By the way, what some coilers
thought
> were "burn marks" on their transformers simply turned out to be very
black
> sooty dust that had been attracted to the transformers when they were
being
> used in the electrostatic copiers they were designed for. I use a paint
> brush and a little compressed air to clean up such dust. The paint brush
> helps to break the stuff loose if it is held on by oil or moisture.
> 
> > One more thing.
> > The safety gap settings are for dry weather or indoors with cool
> > temperatures.  High humidity or temperatures (inadvisable) will
> > drastically change this.
> > Barry
> > 
> 
> My thanks to Barry for taking the time to share with us his knowledge
about
> these transformers.
> 
> Fr. Tom McGahee