[Prev][Next][Index][Thread]
Re: 10KV RMS -at- 300MA for less than $100
Subject:
Re: 10KV RMS -at- 300MA for less than $100
Date:
Sat, 15 Mar 1997 15:42:25 -0500
From:
"Thomas McGahee" <tom_mcgahee-at-sigmais-dot-com>
To:
"Tesla-2" <tesla-2-at-emachine-dot-com>
Dear Fellow Coiler,
I am sending this compendium of posts to all persons that I am currently
aware of who have purchased the H&R transformers, or who expressed an
interest in buying them. I am also sending this set of posts to the
Tesla
list and the Tesla2 list (Tesla2 is a new list dedicated to helping
beginner coilers.) The good news is that these babies are quite useful.
The
bad news is that I am still awaiting full details on several aspects of
their successful use. Please read *everything* in these posts. The info
is
somewhat scattered throughout the posts.
Bottom line: you *need* a safety gap for each transformer. Failure to do
so
will almost surely result in early demise of these excellent
transformers.
The ones with quick connect connectors are more prone to failure due to
the
position of the inside winding quick connect. Immersion in oil should
eliminate all problems with insulation, but safety gaps are still a
must.
Due to the large currents produced you need to use a large (such as .06
mfd) HV capacitor in tank circuit. Otherwise your spark gap will flame.
The
spark gap has to be really heavy-duty, as the currents are high.
As I get more information in, I will make sure that it gets posted to
the
Tesla list and the Tesla2 list. I am sending the current posting to
individuals as well as to the list since I want to alert users of this
transformer as soon as possible so that no one else unneccesarily
damages
one of their transformers.
I know that the urge is to just slap these babies into an existing Tesla
system as-is. That could be disastrous. It would be a real shame if
these
transformers got a bad reputation simply because we didn't take the time
to
implement them properly.
You will note that my own experiments were run without using the
resonant
winding and its associated capacitor. Thus I was only generating 1/2 of
the
available voltage. That may explain why my abuse of the transformers did
not result in any damage. Personally, I am waiting until Barry Benson
answers my second set of questions before I attempt to run these suckers
in
resonant mode. I plan to oil immerse the secondaries first!
Please share with the rest of us your experiences with these
transformers.
I hope to take all the information we gather on these things and create
a
fact sheet so that others can benefit from what we learn.
Please be careful! There is a *known* failure mode related to the
secondary. Thus we should all be able to work around this failure mode.
Some may try oil immersion. Others may try moving the secondary
connections
after careful disassembly. Some may try additional insulation such as
RTV
silicone, etc. Whatever you do, please let me know both about your
successes and any failures. Be as explicit as possible about what you
did.
Your information is only useful if it is complete and exact. For
example,
if using RTV silicone, let me know what brand, how much you used, and
any
nitty gritty details that will help others duplicate your success.
I would appreciate it if all users of this transformer would send me
copies
of any e-mail discussing these transformers so that I can gather all the
relevant information into a single document that we can post to the
lists
and get into the archives.
Fr. Tom McGahee
----------
> From: Tesla-2 <tesla-2-at-emachine-dot-com>
> To: tom_mcgahee-at-sigmais-dot-com
> Subject: Re: 10KV RMS -at- 300MA for less than $100
> Date: Friday, March 14, 1997 9:42 PM
>
> From: Steve Falco <sfalco-at-worldnet.att-dot-net>
> Date: Fri, 14 Mar 1997 21:42:12 -0500
> Subject: Re: 10KV RMS -at- 300MA for less than $100
>
> > Those transformers may not be suitable as TC power supplies. It
> > appears that they may be ferro resonant transformers and even more
> > fragile than neons.
> > I was tempted to get a couple myself but I'm waiting until
> > someone actually reports results.
> > The verdict is still out on these. Since you already ordered 2 of them
> > report back to us what results you get. (even if bad)
>
> I ordered four of these transformers. One had quick-disconnect
> terminals and the other three were the "directly connected wire" type.
> I hooked them up as stated on the instruction sheet, with the provided
> capacitor to resonate the iron core.
>
> I wired the secondaries in series and the primaries in parallel to get
> 10kv out with 120v in. I found that I had to tighten up my spark gaps
> considerably to get the coil to fire (I had been using a 12kv neon).
> The spark gaps had a much greener look from the vaporizing copper
> because of the increased current drawn. I suspect the gaps would not
> last very long with 3 KW of power applied!
>
This is an important point. The increased current will indeed chew up
spark
gaps more quickly. This should come as no big surprise to any of us. The
tuning of the gaps is obviously also an issue. You can't just throw
these
transformers in a system an not expect to have to do some tuning and
upgrading of the spark gap system. The extra current availability of the
transformer requires that the capacitor be bigger, otherwise the spark
gap
will flame instead of spark. Again, this is not a defect in the
transformer, but something that must be contended with when increasing
the
available current in any Tesla coil system.
> The spark output was down considerably from my 12kv 30ma neon presumably
> because of the lower voltage and because the spark gaps were overloaded
> badly. A much bigger main capacitor might have helped soak up the extra
> current available.
>
Absolutely correct. Unless a larger capacitor is used, the spark gap
will
flame and power will be *lost* instead of used.
> Sadly, the transformers only ran for a few seconds, then I saw smoke.
> Turned out the transformer with the quick-disconnect terminals arced
> over between one of the high voltage terminals and the secondary
> windings. I'm afraid this transformer is totalled, because the paper
> insulation between the secondary layers charred away.
This is precisely the problem that Barry Benson had with his first
attempts
at using these transformers. The ones with the high voltage wires tend
to
stand up better. The manufacturer has both quick connect HV terminals on
the same side of the transformer, and fairly close to one another. But
the
real problem here is that the wire from the center of the secondary coil
has been brought up to be on top of the secondary so that the quick
connect
terminal can be soldered to it.
In normal operation this appears to work OK, but in Tesla service the
kick
back voltage can initiate a spark between the inner secondary wire and
the
outer portion of the secondary. Once a spark has begun, it ignites with
a
vengeance because of the current available.
It seems to me that immersion in oil and removal of all air bubbles
after
immersion would totally eliminate this failure mechanism. To facilitate
the
removal of air bubbles it might be useful to carefully perforate the
protective layer that currently covers the secondary.
The transformer looks like it would be very easy to dismantle. If this
was
done, then careful unwrapping of the outer insulatory material might
allow
one to attach High Voltage insulated wire in place of the quick
connects.
Barry Benson mentioned that he packed his transformers with RTV silicone
for increased HV safety. I assume that he meant that he did that to the
secondary windings after disassembly.
Note that if you use oil immersion you should be able to get by without
having to worry about re-wiring the quick connects, because the oil will
provide adequate insulation.
Another very important thing that we can do to prevent these
transformers
from self-destructing is to use a good protective spark gap *at each
transformer*. Please do not skimp here! Even if oil immersed, this item
seems to me to be very important! Do not try to protect all the
transformers with just one protective spark gap! Use a separate gap for
each transformer. Begin with the gaps set too close, and then widen the
safety gaps until they don't fire anymore. This will go a long way
towards
protecting these transformers. Do not omit the safety gaps!!!
>
> I'm not sure if I should send back the two transformers I have not
> touched yet or keep them. At a few seconds of operation per
> transformer, they are pretty expensive. If they can be made to hold
> together they would be fantastic...
>
Steve, these transformers require some special care, but I believe that
in
the end the extra effort will be worth it. I am still waiting for word
from
Barry Benson as to further details concerning what we have to do to get
these transformers working in a safe way. I recommend that all of us
that
have these transformers *WAIT* until Barry Benson (and anyone else that
has
sucessfully used these transformers) can get back to us with full
details.
No sense in any more of us having to learn the hard way what the
"gotchas"
are with these babies!
By the way, Steve, don't throw the ruined unit out. The core is still
useable, as is the primary. You should be able to use the remnants to
build
something useful, such as a primary choke. By adding a heavy duty
shorted
secondary (just a few turns of really *thick* wire or rod or bar stock),
you can have a mini equivalent of a shorted arc welder. for use in
driving
a primary circuit.
Below I have appended some additional stuff that I hope is useful to all
who have bought these transformers.
> Steve Falco
> sfalco-at-worldnet.att-dot-net
>
>
----------
> From: Mike Hammer <mhammer-at-misslink-dot-net>
> To: Thomas McGahee <tom_mcgahee-at-sigmais-dot-com>
> Subject: H&R transformers
> Date: Friday, March 14, 1997 6:28 PM
>
> Fr. Tom,
>
> I guess by now you know that you have created a minor
> upheavel in the coiling community when you told us about
> the transformers that H&R has.
> I received 5 emails today alone from people asking me
> if these transformers are for real.
> It seems almost too good to be true.
>
> Well some people have cast doubt on the suitability of these
> because of them being ferro resonant devices.
>
> I once used a ferro resonant transformer from a large IBM copier
> that sounds similar to these and it expired rather quickly.
>
> So my question is do you have a pair of these?
> Have you done any tests on them?
> Have you run them on a coil?
> Any info would be helpful.
>
> I would like to get a pair of them myself but
> I firmly believe that if something seems to good to be true
> it usually is.
>
> TTYL!
> Mike Hammer
> mhammer-at-misslink-dot-net
Mike,
I have been busy trying to gather all the info I can both by
experimenting
with the two units I bought, and by checking with people that I know
have
experienced success with these units.
Since you expressed a desire for this information I am attaching some of
my
experiments, one of my queries, and the response I got so far.. as you
will
see I followed it up with a request for more information.
The good news is that these puppies are really quite useful, even though
some people have had some bad experiences with them. Barry's experience
shows both the problem aspect, but even more importantly, the final
great
result that can be had with a little patience.
These transformers are a bit out of the ordinary, that I will admit! For
me
the bottom line is useful results. And Barry Benson is one user who has
used them with success. You may want to wait until he answers the second
set of questions I sent him. I'll tell you this much: if I had the money
I
would order another one or two myself and see how far I can push these
suckers! I would want to oil immerse them first, though, as they are
*not*
indestructible as they come out of the box. But a little oil can easily
clear up *that* problem!
Please keep in mind that I am new to these transformers myself. I, too
have
a lot of questions. But from what I have already seen of the two units I
bought, I would have to say that they were worth what I paid. Stay
tuned!
Hope you find this useful.
From: "tom_mcgahee"-at-sigmais-dot-com-at-PMDF-at-PAXMB1
To: Benson Barry
Subject: H&R Transformers
Date: Tuesday, March 11, 1997 9:09PM
<<File Attachment: 00000000.TXT>>
Barry,
I included information you posted on February 11 to Malcolm Watts in the
following post that I have sent out to the Tesla list. I am sending this
copy direct to you, because I would appreciate it if you would send a
post
concerning your use of this type of transformer to the Tesla list under
the
subject heading "RE: H&R Transformers"
In particular, if you could share with the rest of us your impression of
this transformer, and any pertinent details about using it that you can
share with us. Like, did you remove the shunts? Do you use the AC
capacitor
that it came with? Are you happy with the transformer? I know that you
are
probably very busy (as we all are), but this is something that you could
share with us that would be most useful. I will be looking foreward to
hearing from you. I would appreciate it if you would CC me a copy of
your
response when you send it to the Tesla list, as this will allow me to
read
your response earlier.
Thank you for helping Malcolm, by the way. I hope that I can perhaps get
you to fill in a Project Coiler form some time in the near future.
Project
Coiler is my ongoing attempt to gather information on operational coils
and
make this information available to all interested persons on the Tesla
list. I have a standard form that helps to organize this data in a way
that
will hopefully be useful to many coilers.
Fr. Tom McGahee
Here is Barry Benson's response:
Benson_Barry%PAX5-at-mr.nawcad.navy.mil
TRANSFORMER, PHOTOCOPIER, H & R
Hi Fr. Tom McGahee, All,
I started using these transformers after seeing
a system built with them in the T.C.B.A. news. I have been
able to get 56" of spark with 120VAC before tripping the
breaker with a 6" X 27" X #18 gauge magnet wire wound
secondary terminated with a 4 X 20" toroid using a 0.06 uF
capacitor and 14 point X 10" diameter X 1725 RPM driven
rotary wheel using 8-32 stainless steel screws with 4
parallel sets of 1/8" stationary tungsten rods.
When I first bought a pair of these transformers 10 years
ago I cooked both of them. The high voltage winding lead out
was put too close to the low voltage side of the winding.
When stressed with Tesla coil use without protective gaps
it arced over and made one the transformers useless. I
rebuilt the other by scraping off the carbonized insulation
and repotting with RTV. I now run with safety gaps and
a 4" X 3" X 1" cross section cored common mode choke
with 100 turns for each side. This limits the current and
protects the transformers from RF spikes. I ordered a
new transformer recently that came with silicon rubber
insulated wires for the high voltage lead. This is a vast
improvement.
These are serious transformers. They are like mini
pole pigs. I suppose that if you put one in oil that it
would be indestructible. I have been thinking of using
six of these transformers with primaries in series parallel
for running 10 KW off of 220 VAC.
Barry
----------
Barry,
Thank you ever so much for responding to my request, and for sending a
copy
to the Tesla list. Forgive me, but I have a few questions to ask. They
may
seem trivial to you, since you have been using these type transformers
for
a while, but there are many of us who are only beginning to use them.
1) Do you use the resonating winding at all? The capacitor?
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"?
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?
4) Of the failure modes you have experienced, what were they, and how
can
they be reduced?
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.
6) The common mode choke you mentioned: is this homemade, or can we buy
one
somewhere? Details?
There are a fair number of Tesla list members (myself included) that
have
just acquired a few of these puppies, and many more looking on from the
sidelines to see what becomes of our venture. Your practical experience
in
this matter can be of great benefit to all of us. I hope that my request
for more information does not put you out, and on behalf of all of us, I
thank you again for what you have already shared with us!
Fr. Tom McGahee
*****
Fellow Coilers,
Had a few hours yesterday and today to do some experimenting with the
two
H&R
transformers that I have. At the moment I have only one Tesla Coil set
up
in my shop. All the others are in various states of disarray as I am
attempting some other experiments with various component parts of the
systems.
The working Tesla coil was being used with a 7,500 volt -at- 60 ma
transformer. Not your standard transformer, but that's par for the
course
around here, where most everything is scrounged rather than bought.
Anyway,
I disconnected the regular transformer and connected up *two* of the H&R
transformers with their primaries in parallel and their secondaries in
series. I did *not* connect up the resonant capacitor that was supplied.
Spark gap used was a single variable static gap (because I wanted to
test
the transformers at the extreme by opening the gap all the way out to
where
the spark gap stopped firing. For all these tests I removed all chokes,
as
I wanted to see if the transformer was prone to failure).
The results are: the secondary coil produced a spark that was twice as
long
and much
hotter than with the original transformer. I attribute this to the extra
current capability of the H&R transformers. Please note that I was *not*
using the transformer in its resonant mode. In its resonant mode it
produces 5KV per transformer, but without the resonant mode it acts as a
2,600 volt 300 ma straight transformer as far as I can tell. That means
that together the two transformers were producing about 5,200 volts at
300
ma.
While I am disappointed that the 5KV rating per transformer could not be
attained in straight transformer mode at 120 AC input, I am still happy
with my purchase. I ran the poor thing for 15 minutes continuously as a
sort of torture test. The transformers were just barely warm at the end
of
the test. In fact, they were almost cold.
*** note: I am waiting for input from Barry Benson as to whether or not
he
uses the resonant winding or not. Until then I am *not* using the
resonant
winding, because this way I am using it as a straight transformer. The
fact
that I have not burned up my transformers despite the abuse I have been
giving them may be due to the fact that I am *not* using the resonant
winding. I will wait until I hear from Barry Benson before attempting
*that* part of my experimentation!
***
I am interested in seeing what these transformers will do when driving a
decent multiple static gap. By the way, quenching becomes even more
important as you increase the *current* supplied by the transformer. If
the
arc is not blasted with air the spark gap spark can begin to flame. My
single static spark gap looks more like a Jacob's ladder or flamethrower
when I turn off the blower. If the gap is allowed to become too hot,
then
it flames and secondary spark activity decreases accordingly. This is
not
due to any defect in the transformers being tested... it is just what
happens naturally with higher input currents. Make sure you have a spark
gap setup that can handle the increased currents! Otherwise you will get
disappointing results.
I tried running *one* of these puppies with 220 volts on the
primary in straight transformer mode. The core must have been
saturating,
because the quality of the spark at the spark gap changed drastically.
The
primary warmed up considerably, so I terminated this part of the
experiment
after only about 4 minutes of testing. I definitely do not recommend
running these things too much above the rated primary voltage. Looks
like
you can push them to 150 VAC with little problem, however, so you can
crank
up your variacs on these! *** oil immerse first, please!***
At 220 VAC there was no permanent damage done to
the transformer, but it did heat up, and the output became very
flame-like
at the spark gap.
*** I was foolish to try this, but since it was my post that has
persuaded
a number of others to stick their necks out and purchase some of these
transformers for themselves, I feel a certain moral obligation to do all
that I can to make sure that no one else has to unnecessarily destroy
one
of these transformers.
***
By the way, I have been informed that H&R is supplying several
variations
on this transformer. One of them uses quick connect terminals and is
very
clean looking, and the other model has insulated wires for all the
inputs
and outputs. This second model is the same internally, but does not look
as
"spiffy" as the first model. They work identically and have the same
ratings.
*** It turns out that the one with quick connect terminals is less
desireable, as it has more of a tendency to flash over. Read the reply
from
Barry Benson for more details.
***
I am sorry that these transformers are not exactly as great as I at
first
thought they were going to be. However, it turns out that they are still
quite useable. My tests indicate that it should be possible to run at
least
three and possibly even four of these with the secondaries in series.
***
in oil! ***
Remember that the insulation is designed for 5KV operation per
transformer,
and that without the resonating
capacitor the voltage out is about half that. Exercise prudent caution
with
these transformers. The raw arcs really flame up! If you are concerned
about the level of high voltage when putting these in series, you can
opt
to connect the secondary center tap of the two-transformer pair to a
Good
RF Ground.
There is no need to remove the resonating winding... just don't connect
anything up to it.
*** I am waiting for more information before I attempt to use the
resonating winding. When it is forthcoming I will communicate it to the
Tesla list.
***
Several people asked about using these transformers for Jacob's ladders.
Two of them in series make a pretty good Jacob's ladder. You might want
to
try playing around with using the resonant winding and its associated
capacitor in this application. There are several possible combinations
that
can be tried. Be aware that the arc is quite HOT, and it will melt metal
electrodes quite readily if the arc is allowed to stay in one place for
more than a fraction of a second. Mine chewed up a chunk of #12 solid
copper wire and spit out little metal balls. So your metal electrodes
need
to be something that can take the heat. I only ran a quick test for
Jacob's
ladder operation. Enough to show me that the arc produced is very nice.
I
did not run an extended test to see if the transformers got warm or
anything. I'll leave that to someone who has nothing better to do with
their transformers. I'm putting *my* two transformers into permanent
service on my present coil. And I hope to maybe add another transformer
in
the near future to raise the voltage level up a bit higher.
Someone asked about putting these units in oil. It looks like they would
operate well in such an environment. If you do this, you might want to
carefully perforate the outer protective covering on the HV winding so
that
air bubbles can be more readily removed. I will be running my two
transformers as-is for now, and if I experience any future difficulties
I
will report them to the Tesla list.
*** Note: It is extremely important that *each* transformer is equipped
with a safety gap. This one little item alone can save you much grief. I
did not use safety gaps during any of my experiments, but that was very
foolish. It appears that the major failure mode for these transformers
is
related to internal flash-over arcing when used for Tesla service. This
is
especially the case for the units that come with the quick-connect
terminals. Failure to observe safety precautions mentioned can result in
very quick destruction of the transformer. If at all possible, oil
immerse
the transformer. I found a sort of rectangular plastic container at the
local plastics store that is just large enough to hold two of the
transformers. I am goind to bolt the two of them together using short
metal
strips so that they will not shift relative to one another. I will use
30KV
HV silicone wire to connect the transformer secondaries to HV terminals
that I will install on the lid. I am going to bring out the HV center
tap
as well as the two end HV wires, so that I can attach a separate safety
gap
to each secondary. The primary wires will also be brought out to the
lid.
Since the oil insulation is really only needed at the secondaries, I
plan
on stuffing the container with non-conducting stuff that is heavier than
oil. This should greatly reduce the amount of oil I have to use to bring
the level up so that it covers the secondary with an inch to spare. It
will
look awful, but this should save me a couple of bucks.
***
It is evident that the increased current capability over that of a neon
is
very desireable. I will continue to look for other high current
transformers that can be used in Tesla coil applications.
Fr. Tom McGahee