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Sean wrote "I dissagree"
That is your prerogative.
Sean wrote "You mean to say that the pull in current is never more than the
holdin current. My understanding of a coil, solenoid or contactor is that
pull-inin current is greater and the hold-in current less due to the
increasedinductance due to the magnetic circuit being closed. Also it is
apositivedesign feature as as the pull-in forse is greater than the
holdinforse. acontiuous cycle of opening and closing would give an overall
aversgeincreased power consumption. Increased power consumption =
increasedpowerthat needs to be dissipated."
No, I never meant to say that at all. You are perfectly correct in what you
said above. However, the minimum pull in current is exactly that, minimum.
This is a specified parameter that tells one at what current the contacts
will close. The minimum hold in current is exactly that too, minimum. This
is also a specified parameter that tells one at what current the contacts
will remain closed. Now, in the system that we're discussing, simple
application of relays to conventional, albeit experimental, aircraft systems
the current through the coil in the stable on state will be significantly
greater than either the pull in and hold in specified values. There is an
example below of an Omron relay which is typical of most electro mechanical
relays...
Omron G8J-1C6T-F-DC12
Operating voltage 12VDC
Coil resistance 78 Ohms
Pull in current 115mA
Hold current 15mA
Nominal current 154mA
Contact rating (resistive) 35 Amp for the normally open pair and 20 Amp for
the normally closed.
As you mentioned the pull in current is indeed much greater than the hold in
current, but as you can also see that the nominal current at 12VDC is
greater than both.. So if one had to design a more complex system that took
advantages of these differences then you would be right in that a greater
power would be dissipated with frequent activation and de activation of the
relay. But this is not the case in the simple set up we normally put in
airplanes. KISS.
Sean wrote "May be I have miss understood something. Yourcomments contradict
what have learnt in college, experienced inpractice andinformation
researched in ctalogue from Allen Bradley to Sprecher andShuh."
I think perhaps you had misunderstood something. My previous comments never
addressed the hold in and pull in currents as this was moot in the
particular system under discussion. I hope this clears it up.
Keep the shiny side up and right rudder (perhaps left rudder down under?)!
Pat Weston
VP of Engineering
Diamond Multimedia Systems
Communication Division
360 604 1538
LML homepage: http://www.olsusa.com/Users/Mkaye/maillist.html
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