High Voltage component

[duke37]

I have repaired various electric fence units and there are some components connected in series/parallel across the output. They are light brown with a white end. I have never changed one of these even if the diodes have been blown apart. They seem to have no connection. Any idea what their purpose is?

 

[Bluejets]

Inductors perhaps..??

 

[Gryd3]

Inductors perhaps..??

The white caps on them make me feel they are polarized... Could they be diodes perhaps?

 

[davenn]

They seem to have no connection. Any idea what their purpose is?

They appear to be connected between other components

Im picking ... probably resistors .... see if you can get a resistance measurement across them

 

[duke37]

They show no connection.
If they were inductors, the wire would need to be mighty thin.
At the time I looked at this fencer I did not have a capacitance meter.

My thought is that they could be a diode with sufficient series elements to appear open circuit on a normal low voltage meter or maybe a spark gap.

 

[Arouse1973]

Could they be lightning suppressors?
Adam

 

[Gryd3]

Could they be lightning suppressors?
Adam

Point for being creative... but lighting would have enough potential to arc across those traces and components wouldn't it?

 

[Arouse1973]

Point for being creative... but lighting would have enough potential to arc across those traces and components wouldn't it?

No, thats the whole point. Think about how they work.

 

[Gryd3]

No, thats the whole point. Think about how they work.

I glanced at lightning suppressors a while back. Aren't they just a spark gap to ground?
Larger gap would allow for a higher voltage to remain in the system. It very well could be a lightning protection circuit.. but I am not familiar with different kinds of suppressors to say one way or the other with certainty... I'm still eye-balling the white caps on one end... Thinking they have some significance. Hopefully someone can come in here and say "You're all wrong, those things are..."

 

[davenn]

No, thats the whole point. Think about how they work.

No, it arcs across those and everything else on the board, everything gets toasted

I still go with resistors for current limiting
I still remember the days in the older TV's where you would see a number of high voltage resistors strung together in the EHT lines to do current limiting .... I see this as the same sort of thing

For a short time I did consider them as diodes as part of the diode multiplier but that isn't correct.
You can see the diode and capacitor multiplier along the back of the board

 

[Gryd3]

No, it arcs across those and everything else on the board, everything gets toasted

I still go with resistors for current limiting
I still remember the days in the older TV's where you would see a number of high voltage resistors strung together in the EHT lines to do current limiting .... I see this as the same sort of thing

For a short time I did consider them as diodes as part of the diode multiplier but that isn't correct.
You can see the diode and capacitor multiplier along the back of the board

Makes sense. 3 groups of parallel components string together in series. I've done something similar with lower wattage resistors to make an equivalent resistor to handle a larger load.
There is a spot for a third component to add in parallel to each group as well..

 

[Arouse1973]

I glanced at lightning suppressors a while back. Aren't they just a spark gap to ground?
Larger gap would allow for a higher voltage to remain in the system. It very well could be a lightning protection circuit.. but I am not familiar with different kinds of suppressors to say one way or the other with certainty... I'm still eye-balling the white caps on one end... Thinking they have some significance. Hopefully someone can come in here and say "You're all wrong, those things are..."

Agreed if a direct lightning strike hit the wires then game over. But this is not as common as you may think. The lightning stroke that hit's the ground generates a massive electric field which will induce currents into fence wires as they are basically long antennas. It is this that the lightning suppressors are designed for, the secondary effect.

Some people also put a small coil on the fence wires to give some extra inductance to slow down the rate of change of current. This gives the suppressors something to work on and thus clamping the high voltage to a much lower value which prevents damage to the circuit. Suppressors can be spark gaps or GDTs or MLVs or diodes. But I must admit I am siding with Dave here that they could be some sort of resistor.

Adam

 

[Bluejets]

Could also be transient voltage suppressors (TVR) ....... quite a good read here...... www.google.com.au/patents/US7944669


Edit:..If link doesn't work just put the number into a google search......

 

[Gryd3]

Could also be transient voltage suppressors (TVR) ....... quite a good read here...... https://www.google.com.au/?tbm=pts&gws_rd=ssl#tbm=pts&q=US+7944669

Edit:..If link doesn't work just put the number into a google search......

Haha. If that's true, they look like resistor and diode combo components. So I could have been half right

 

[Bluejets]

Mmm, good educated guess on your part.

Just goes to show that studying theory always pays sooner or later.