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Re: Relays and Contactors
Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>" <davep-at-quik-dot-com>
Tesla list wrote:
>
> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Mddeming-at-aol-dot-com>
>
> In a message dated 2/5/02 10:58:01 AM Eastern Standard Time, tesla-at-pupman-dot-com
> writes:
>
> >
> > During the past I've seen arcing from connections being pulled apart,
or any
> > situation interrupting high currents.
> > The planned current load will be 240vac -at- ~20amps continuous duty. What
would
> > prevent excessive arcing when the contacts open under full load? Is there a
> > difference between relays and contactors in this respect?
> >
> > I will be using Variacs to ramp up power and back down again but if the
> > deadman's switch opens at full power....??
> >
> > Rick W.
> > Salt Lake City
>
> Hi Rick,
> FWIW, I use a contactor rated at 2-3 times the load in my power
> cabinet. As to the etymology of the words: I believe that the term
"relay" came
> out of the communications industry, where "information" was going through the
> contacts, while "contactor" came out of the electrical industry, where the
> stuff going through the contacts is pure power. As such, contactors are often
> designed with a spring loading to minimize the time the contacts are within
> arcing distance of each other on opening. Operationally they are the same.
> Think of a contactor as "a fast-opening relay on steroids".
I would differ, mildly, (having done relay design....)
Relays can be and are used for 'power'.
Relays come in various speeds.
Relays are usually faster than contactors.
Contactors are best, i think, thought of as
Big Thumping Relays
Additionally, contactors are more likely to have
'features':
May include auxiliary (low powered) contacts,
for control, or signalling.
May include built in overload protection.
(etc....)
best
dwp