Arcing

[peavey_wolfgang_2000]

Hi Guys, wolf here again, still putting along when I get a chance to learn how to program PLC's,

Anyhow got my PLC simulator for my PC, I am excited to get to learn it better....but anyhow,

My question is this......

Arcing is caused by switching....

(a) inductive loads
(b) capacitive loads
(c) high voltage loads slowly
(d) resistive loads
(e) mechanical loads

This is a lab simulation, since I have no classroom, I am asking for some help in this matter!!!

Wolf

 

[leitmotif]

Peavey

I would say all
EXCEPT mechanical loads
ASSUMING all switching is done only by mechanical methods.

Dan Bentler

 

[DDOBSON]

Any load depending on how and when its switched.

 

[rdrast]

Arcing is caused by switching....

You could have stopped there.

 

[stasis]

I have to agree...unless the power is off when switching, there will always be an arc of sorts as electricity doesn't like to loose it's path to ground. When switching, an initial contact of a load with a power source will create an arc, even if it isn't visible.

 

[jstolaruk]

Reaching way back into gray matter:

Arcing occurs when the voltage potential is large enough and the physical difference between the two potentials is small enough to overcome the dialetric's (in this case air) resistivity.

eeeks!

 

[Rick Densing]

Arcing will be most pronounced when switching inductive loads.
In and inductor, the voltage across it is proportional to the rate of change of the current going through it.

If you have an inductor coil with current in it and you open the switch, the current tries to go to zero. Since the current is changing rapidly, the voltage across the coil is going to rise very high, very fast. As stated earlier, you will get an arc whenever voltage rises to the point that the air (or other medium) breaks down and conducts electricity. When you mechanically break the circuit, you will get a voltage high enough to cause an arc across the switch contacts.

This is usually seen as more of a problem when using relays, as the off state of the contacts leaves the contacts much closer together than your typical switch.

You can get arcing on any of the loads you mentioned, though I am not sure what you mean by mechanical loads.

 

[elevmike]

If I had to pick JUST ONE, it would be inductive loads. However all loads cause arching of some sort...just to varing degrees...

 

[Eric Nelson]

Some good 'visual' examples of arcing...

http://205.243.100.155/frames/mpg/345kV_SWITCH.MPG
http://205.243.100.155/frames/mpg/500kV_Switch.mpg



-Eric