HV xformer for fence energizer 1

[GonzaloEE]

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:

http://www.mulehollow.com/retr.html

Thanks in advance for any help!

 

[GonzaloEE]

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.

 

[VEBill]

Sounds a bit like an ignition system...

 

[GonzaloEE]

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

 

[fsmyth]

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>

 

[GonzaloEE]

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!

 

[GonzaloEE]

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.

 

[Pud]

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

Harry

http://www.tynevalleyplastics.co.uk

 

[GonzaloEE]

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

 

[GonzaloEE]

Here's another pic. The one at the right has 4 wires, 2 of them for a fence line monitor. Output screws are on the back side.
Hope it helps.

 

[itsmoked]

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

 

[GonzaloEE]

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!

 

[itsmoked]

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