[TCML] 7.5V 52A Filament Transformer for 3CX3000 Needed

[Jim Mora]

Hi,

I have been down this very road lately. My first attempt was a Double stack
x-ray cores but I failed to get to the 1.5 volt turns we like is was think
120v. A benevolent member send me an in tact primary (#12awg or #10awg 180
turns 900va Neon) I cleaned it up with solvent and am in the final process
of the secondary winding. Hey! I have a 4" long by dual 1.375 winding
window:-))) Ya baby. I am considering making it possible to add taps to 12v
etc. to a phenolic base plate. So best case we have 900Va/10v or 90amps max!

Get your self a neon with a bad secondary!- Lots of winding real estate. I
don't expect my 10v40a will flitch this baby. Microwaves are pushed to the
limit!

I do plan to ramp up the filament with a variac.
Jim Mora

-----Original Message-----
From: tesla-bounces at pupman.com [mailto:tesla-bounces at pupman.com] On Behalf
Of Dr.Hankenstein
Sent: Friday, June 12, 2009 4:22 PM
To: 'Tesla Coil Mailing List'
Subject: RE: [TCML] 7.5V 52A Filament Transformer for 3CX3000 Needed

Normally, filament xfmrs should be chosen to approximate the max load.
The reasoning behind this is as follows:

Filament resistance is very low at start up, thus causing heavy inrush
current that could damage the filament.

By closely matching the xfmr impedance to the filaments' maximum
operating  current, the inrush can be greatly reduced, resulting in
longer filament (and tube)life.

One could, of course, use a variac (or other current limiting device)
and bring on the current slow and easy for even better results. 

Hank

-----Original Message-----
From: tesla-bounces at pupman.com [mailto:tesla-bounces at pupman.com] On
Behalf Of jimlux
Sent: Friday, June 12, 2009 6:18 AM
To: Tesla Coil Mailing List
Subject: Re: [TCML] 7.5V 52A Filament Transformer for 3CX3000 Needed

Phillip Slawinski wrote:
> DC,
> 
> Pardon me, but that seems a little absurd.  I can think of many
> reasons not to do this.  To begin with the transformer would make a
> good power source for the tube in question.  Secondly if one were to
> do this, the transformer would be many times larger, and heavier than
> it needs to be.  If anyone has enough 7.2kV pigs to do this why
> wouldn't he just sell one to buy a real filament transformer?
> 
> -Phillip Slawinski


"real filament transformers" are pretty expensive, new, and, as noted by

the original poster, are hard to find used/surplus/cheap.  Oddly, it's 
probably easier to find an inexpensive pole transformer than a 
inexpensive filament transformer.

That said, using a 7.5kVA core for an application needing 400-500VA or 
so is somewhat overkill.  If one has them, a couple microwave oven 
transformers might be a better starting point (yes, a typical microwave 
is 600W, but the transformer gets pretty toasty.. I wouldn't use one at 
500VA for continuous duty).  And hey, the MOT already has a 5V or so 
winding on it.





> 
> On Thu, Jun 11, 2009 at 15:43, DC Cox<resonance at wildblue.net> wrote:
>> If you can't find one, you can do what I did:  remove the outer HV
winding
>> on a 7.2 kV pole xmfr, 5 kVA, then wind on some #6 AWG wire to make
your
>> own.
>>
>> Experiment with 10 turns of finer wire to get the turns ratio right,
then
>> wind on the big wire.
>>
>> Dr. Resonance
>>
>>
>>
>>
>>
>> On Thu, Jun 11, 2009 at 7:45 AM, Cameron B. Prince <
>> cplists at teslauniverse.com> wrote:
>>
>>> Hey guys,
>>>
>>> Does anyone have a 7.5V 52A filament transformer they¹d be willing
to part
>>> with?
>>>
>>> We actually need two if available. Please contact me off-list.
>>>
>>> Thanks,
>>> Cameron
>>> _______________________________________________
>>> Tesla mailing list
>>> Tesla at www.pupman.com
>>> http://www.pupman.com/mailman/listinfo/tesla
>>>
>> _______________________________________________
>> Tesla mailing list
>> Tesla at www.pupman.com
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>>
> _______________________________________________
> Tesla mailing list
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> 

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