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HV xformer for fence energizer

HV xformer for fence energizer

HV xformer for fence energizer

(OP)
Hi all,

I'm looking for High Voltage transformer suppliers for fence energizers. I mean the standard step-up transformer whose secondary wires are connected to the fence and earth.

This is close to what I'm looking for:
www.mulehollow.com/retr.html

Thanks in advance for any help!  

RE: HV xformer for fence energizer

(OP)
Hi all,

I'm confused because most transformer manufacturers I've found, ask for standard parameters hard to find from this application.

As many of you already know, most fence energizers shunt a charged capacitor to ground through the transformer primary and a switch.  The secondary must whithstand some 6-10KV on a 500ohm load, for less than 1ms, while total released energy must be under 3-5J for safety reasons.

How to translate Joules, seconds and peak voltages to VRms, Amps and VAs, as expected by most manufacturers?

Thanks in advance.

RE: HV xformer for fence energizer

Sounds a bit like an ignition system...

 

RE: HV xformer for fence energizer

(OP)
Sounds good.  Some ignition transformers would match these specs, though I've never knew of one of those put to a fence energizer.
Not sure if those comply with safety regulations
 

RE: HV xformer for fence energizer

I have built fence chargers ages ago using an
ignition coil and a vibrator (some of you are
problably not old enough to remember those).
Worked reasonably well; the old ignition coils
output 10-15 kv.  Newer coils will probably be
in the 50 kv range.  I tinkered also with some
made from HV transformers from old TV's. These
also worked, but not as well.  No decent current :)
Nowadays, I probably would try a coil from a
small one-cylinder engine and a simple
transistor oscillator.  Should work.  Non-lethal.

There is a circuit at:
http://hmin.tripod.com/als/andysm/pages/sw-regs8.html#UPC8F
of a fence controller; also some other HV supplies
that may furnish ideas.

<als>
 

RE: HV xformer for fence energizer

(OP)
Thanks for the diagrams. Didn't know it was that simple.

Ignition xformers are a little expensive for production runs, but it's a good idea for prototypes and Lab testing.

Thanks!

RE: HV xformer for fence energizer

(OP)
Got these fence transformers from an Australian and South American fence chargers.  Both have similar designs, so I suspect both were built in Asia, or at least near Australia.  

Both transformers are cast in epoxy resin inside a plastic enclosure.  The outer winding (thin wire) is divided in 8 cascaded sections, with plastic separators between them.

Hope to post some pictures soon -It should help more.
I'd appreciate any info on suppliers of these parts.  
Thanks.
 

RE: HV xformer for fence energizer


The transformers cast in epoxy sound like spark generators for gas cookers/central heating boilers.

Harry

www.tynevalleyplastics.co.uk

RE: HV xformer for fence energizer

(OP)
Sorry for the late reply. Here are some pics of the transformer.  It's been incredibly hard to find a partner to build it.  Tried with fence charger manufacturers, sales reps. of pulse ignition coils for diesel engines, etc., none of them heard about these parts.

Some measurements:

Voltage ratio ~1:10 (step-up)
Primary inductance: 300uH
Primary leakage inductance: 30uH
Measured Secondary inductance: 33mH

If you know some supplier of these parts, please let me know.
 
Cheers,
Gonzalo

RE: HV xformer for fence energizer

A common way to get what you need is to cannibalize something else which has a transformer similar to what you want.  Then you can disassemble the similar transformer and re-wind it to suit your needs.  Then when you have a working unit in hand you approach a transformer company and ask, "how much for a bunch of these".  Then they know they don't have to put a bunch of engineering into something they may never make a dollar on.  They see the core style you like and they can characterize the transformer and give you a solid quote that isn't exaggerated to cover their expectation that you didn't really know what you needed.

That's what I was taught to do and have done it several times with good results.

Keith Cress
kcress - http://www.flaminsystems.com

RE: HV xformer for fence energizer

(OP)
I'm taking your advice. We've tried both ways: the default inquiry email with endless parameters, and then shipping a sample.
I wrote to 'Company A' and their quote was very costly (NRE charges, etc.) and long lead times; I guess that's the polite way to say 'No, thanks'.

Then we shipped a sample for 'Company B' (abroad) and didn't hear from them for days.  I'm starting to think of our emails buried in a recycle bin, and pieces of our sample travelling into a trash truck.

Thanks!
 

RE: HV xformer for fence energizer

I would only send a precious prototype to someone I'd spoken with personally...  After sending them a photo of the coil, so they have a much clearer understanding of what you want, I'd suggest how much I'm willing to pay and ask if they think that's a possible price.

Keith Cress
kcress - http://www.flaminsystems.com

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