contact rating for pulsed current
contact rating for pulsed current
(OP)
Looking for a relay/contactor to direct pulse current to one of two fixtures. Pulse is sinusoidal, 8kA peak, 2300V initial, 100us pulse width. 30 sec. cycle time, so small average current.
Would a relay rated at 100A continuous work, and if not 100A, then what? Is a relay a wise idea at all?
One option (I know the voltage ratings are probably too close):
htt p://www.co mponents.o mron.com/c omponents/ web/PDFLIB .nsf/0/1E9 06229E455A 9EC8525720 1007DD583/$file/G9EA-1_0209.pdf
What are the failure modes of such a solution? Cold welding? Magnetic interference from pulse through contacts?
(Just so you know, I'm also considering more reasonable options like a second ignitron or thyristor, but this could potentially be the cheapest solution, and wouldn't require opening up the machine.)
Would a relay rated at 100A continuous work, and if not 100A, then what? Is a relay a wise idea at all?
One option (I know the voltage ratings are probably too close):
htt
What are the failure modes of such a solution? Cold welding? Magnetic interference from pulse through contacts?
(Just so you know, I'm also considering more reasonable options like a second ignitron or thyristor, but this could potentially be the cheapest solution, and wouldn't require opening up the machine.)





RE: contact rating for pulsed current
How about finding something from the Power Transmission industry? They switch such levels every day.
RE: contact rating for pulsed current
One thing I didn't mention is that the relay needs to be less than $250 to be price competitive. I haven't found anything less than $300, and even these have current rating of "only" 150-300A, and usually too low of a voltage rating.
I should probably note as well that the relay will already be closed when it is introduced to said pulse.
RE: contact rating for pulsed current
I now noticed that you hinted at that in your first post.
That's a much easier requirement. 100uS is such a small time that the contact's thermal mass (almost certainly) won't allow any damage from heating. Unless it's localized to such an extent that the peak temperature causes problems.
You should estimate the voltage drop for a range of contact resistances (from new to old).
That you mentioned a price it seems that this is for production, so that raises all sorts of interesting angles.
Give this thread some time to see what others can offer.
RE: contact rating for pulsed current
Current-wise, contactors are generally designed to form part of a type-tested combination starter, which essentially means that the contactor will be fit for continued service after a through-fault of less than a certain magnitude. 8kA is a lot of current, but it's actually a pretty small fault level in utility terms and you won't need a very big contactor to survive it for 100uS. 100us is much shorter than the clearing time of a circuit breaker or a typical motor fuse.
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If we learn from our mistakes I'm getting a great education!
RE: contact rating for pulsed current
RE: contact rating for pulsed current
If you are intending to use this as part of a safety isolation then don't use a relay or a contactor, use a lockable disconnector or switch. Many circuit breakers can fulfil this duty too.
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If we learn from our mistakes I'm getting a great education!
RE: contact rating for pulsed current
As far as putting poles in series, that probably isn't an option due to contact resistance, which I need to keep to a minimum (good idea though!). I'll just have to find a relay that can withstand the voltage. The option I posted earlier seems to fit the bill.
RE: contact rating for pulsed current