Re: Contactor question, Arc Suppressioni

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Yurtle Turtle <yurtle_t@xxxxxxxxx>

Thanks. I'm using a GE 90 amp motor starter, so I'm
not too concerned about doing this myself. Even if I
were, there's no easy way to observe the contacts
while in action.

Adam

--- Tesla list <tesla@xxxxxxxxxx> wrote:

> Original poster: "Barton B. Anderson"
> <bartb@xxxxxxxxxxxxxxxx>
>
> Hi Adam,
>
> Arc suppression is best performed with a series
> resistor and
> capacitor across the contacts or across the load.
> There are no
> default values to use for arc suppression due to the
> various contact
> material, shape, size, and of course, various loads.
> Trial and error
> is best. In other words, literally viewing the
> contacts in a darkened
> room and changing the RC values until arc
> suppression is obtained.
> Usually, this means decreasing the R value (and it
> will be quite low).
>
> For example, about 4 years ago, we had a board at
> work which a
> previous engineer designed. We were getting 20
> boards a week failing,
> all due to excessive material transfer of the
> contact points which
> quickly welded closed, and due to this particular
> relay design,
> shorted power to ground frying the board. Besides
> changing the
> circuit to prevent a short should the contact weld
> closed, I also
> used a resistor and capacitor across the contacts
> "at the relay"
> which was the last to turn off (via new time delay
> just so I could
> direct the arc potential to a particular set of
> contacts). Through
> trial and error, I eventually stopped the relay
> arcing (I think I
> ended up at 0.1 ohms and 100uF) for this particular
> relay. We haven't
> had a relay fail in the past 4 years since this
> effort, so arc
> suppression really does work when it's done right.
> Of course, if some
> engineer down the road changes the relay (or if the
> manf. makes a
> change), then we may begin to see failures and go
> through the routine
> again. Of course, if it was mechanically designed
> "smarter", none of
> this would have been necessary. ;-)
>
> Take care,
> Bart
>
> Tesla list wrote:
>
> >Original poster: Yurtle Turtle <yurtle_t@xxxxxxxxx>
> >
> ><snip> Also I've heard of folks placing
> >capacitors across the contacts, to minimize arcing.
> >
> >Adam
>
>
>