Hey,
So I am trying to figure out the problem onto an electric fence (for cattle, advertised 3J 10kV).
(The main power here is 230v, 50Hz)
Peoples already hepled me figuring what a component was.
So here is a schematic:
(schematics on QUCS: regular_sch.PNG)
So my understanding is:
the left side is supposed to provide the power to the circuit (left of the transistor here, which actually a TRIAC).
So the C3 capacitor (25µF) get charges and could reach up to 650v~(230*sqrt(2)*2)
I know it used to reach about 420v before triggering though.
Here is a simplified version of the triggiring side:
(schematics w/ grouped resistors: simplified_sch.PNG)
So the pulse tranformer and the C3 capicitor (25µF) would provide the voltage divider (1.48M/(1.48M+2.21M)).
(I know right, the voltage divider formula works if the output current is zero but there, I think the final voltage is relevant)
Therefore multiplying the voltage by 0.401 to gives charges to the C2 capacitor (4.7µF).
That would yield a maximum voltage of 260.82v (=650.44v*0.401)
So I replaced the original DIAC by a DB3 which should be about 30v-32v (threshold).
Let's take 30v for the maximum best case.
So the charging ratio would be of 11.5%~(30v/260.82v)
Which according to this website (rc circuit basically charges up to 11.5%) (:http://sim.okawa-denshi.jp/en/CRlowkeisan.htm)
Which would be about 2.1sec to reach the 30v (2.21M+1.48M 4.7µF) (R4+R8 w/ C2)
Then the discharge circuit would be triggered (allowing a current pulse through the pulse tranformer).
Another R-C would be formed when the DB3 diac would conduct (221ohm w/ 4.7µF) (R8 w/ C2)
The datasheet of the triac says (nxp bt139-600e) 1.6v to trigger it.
The discharge ratio would be 96.6%~95%~(=(30-1.6)/30).
The discharge time would be 3.1msec.
Making a cycle 2103msec.
Question:
Did I made an error ? (I think I got a PEKBAC problem, aka I am probably making a very obvious mistake)
Because I measered a 901ms cycle so I suppose I am wrong somehow, and I can't figure why my TRIACs and DIAC keep being fried for some reason...
If you guys want to know what I already did:
https://www.eevblog.com/forum/repair/electric-fence-with-an-unknnown-component/I did some more testing but I am pretty much out of ideas (maybe I need to suppose it is a faulty diode)
Basicaly, I can diagnose the symptom but not the cause, therefore I keep frying components.
Thanks for reading.