It would appear that there is some interest in fencing units.
For those folks that want a high impedance toy fencer using a ignition coil or similar, stop reading now... this is not for you.
If you want to build a fencer that can do 70-100 kms of fence, and can transform 12v into 10000 volts@150-200kw, then this is for you... yes ytou read that right, over 100000 watts is easy, 200000is doable, and I have seen 250000 watts when I have turned it up too far.
This means we will be pushing out up to 40 amps@ many thousands of volts if the fence is heavy ( grassed), and probably only 5-15 amps@ 9000v into a lightly grassed fence. The normal/standard measuring level is 500 ohms.... I happen to have lots of 560 ohm 20 watt resistors, so I use them for testing most times..... the current will be volts/560, the power will be volts x current.
The transmission will be DC, but will behave as a high frequency AC wave front, so there will be different voltages along the fence... sometimes higher than where it connects to the fence miles away. It will depend on the fence, the surroundings, the loads, and the inductive and capacitive effects of the fence.
We get to change some of the behavior by changing the impedance of the transformer primary, and the path to the primary from the cap and triacs.
The lower the impedance of the transformer, the shorter the discharge time will be, and the higher the power. The down side is that the spike is so thin, it is easier to stymie with resistive and inductive loads in the fence, and generates a fair bit of RFI ( radio interference )
To stop this we shape the waveform by using an inductor in series with the primary to "slow" the current down a bit ( widen the wave and make it less steep), and some capacitance to help with the shape too. This pulls the peak voltage down, and widens the wave.... makes it a bit more sine like... if you stretch the imagination a bit ( lot)
The circuit board looks like this.
A better one can be found here:
http://www.anotherpower.com/board/index.php/topic,731.msg10716.html#msg10716, with a circuit that is almost right above that thanks to Dario
That thread will give you plenty to go on to build the unit.
Here we will concentrate on the transformer... the important bit.
Ok, we need a microwave transformer, and we can use it a number of ways.
....... the victim....
We can use it like a normal EI transformer, but real estate gets pretty fine in the winding window, and we can make one just as good and lighter if we modify it slightly. It is going to be saturated anyway, so good transformer theory is dead..... so we get the transformer and start by cutting the weld on one side so we can "open" it.... like this..,.,
So now we need to undress it from the coils.... I use a 50 ton brake press normally, but this time I will use a vice and the trusty chisel
And remove the first coil......
then the chokes ( this was a ferro resonant transformer, and was designed to run saturated anyway) and the heater winding/coil for the magnetron
and then the secondary
So we now have choices.... we can cut it up like this:
or we can get to this by cutting off one end instead..... both will get us a C core style.... some of the advantages of the torroid is there somewhere too.
So I cut it to look like this:
Either one will end up with a C core, but there is more meat in thicker laminates using it like this..... and less cutting too......
Off to the next post..... winding the thing.
.,.........oztules