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Thread: Arc guards
09-27-2012, 09:42 PM #1
What is the purpose of the metal squares underneath the cover of three pole contactors? I have heard them called arc guards. I know a lot of people throw them out the first time the points are checked.
09-28-2012, 04:55 AM #2
They are arc guards or also called arc chutes. Their purpose is to give a path to the arc that is created from the inductive "kick" when the contactor opens. They are there for safety purposes.
The inductive kick is a result of an electrical property called inductance, a property caused by any electrical load that has windings, motors, transformers, etc. Inductance tries maintain current flowing in a circuit when the contactor opens. Of course, when the contacts are open enough, the current cannot maintain flow.
Again, the arc guards are a safety feature to capture the arc of each phase, to keep them from meeting each other.
I hope this helps.
AllenUA Local 602
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09-28-2012, 08:21 PM #3Professional Member*
- Join Date
- Jul 2007
- The Hot South
09-28-2012, 09:32 PM #4
Too lazy to put them back when they fall out.
09-28-2012, 10:44 PM #5
They always piss me off when you try to be careful and they fly allover. Like R123 said they are there for a reason so I collect them all up and put them back in. One of our managers told us to leave the covers off contactors so we can inspect them faster on service checks (what a joke).
09-29-2012, 12:32 AM #6Professional Member
- Join Date
- Jul 2000
The possibility\ probability of a phase to phase short goes way up with the arc shields removed. That is especially true at 480 Volts.
When the contacts try to pull off, the bigger arc is created because the contacts were carrying a load. I have seen contactors burned up from the combination of arc shields removed and a low humidity day.