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"AC Inductive Load PF"

A

Andre Majorel

Jan 1, 1970
0
Saw this in the specs of a momentary switch :

Note: AC Inductive Load PF = 0.6 - 0.7
DC Inductive Load L/R = 7 msec

I suppose I should be ashamed, but... Someone care to tell me
what "PF" and "L/R" mean here ?
 
E

Eeyore

Jan 1, 1970
0
Peter said:
Yup.


Not sure about L/R.

That is exactly right, as consider a dc suppy to an inductive relay
coil, the operating switch has to be able (reliably) to break the coil
current. But being inductive, there is a much greater amount of
arcing at the switch contacts. So a contact, or switch must be rated
for its voltage, current carrying capacity, and its load breaking
ability (especially when there is inductance in a DC circuit).
And of course, the greater the L/R ratio, and higher voltages, then
greater arcing will occur, to the extent that the contact nay not be
able to break the arc at all if it does not have an adequate rating.

Nice to see it so well explained. I've never seen L/R specified before but I'm
not into heavy power where it's likely a more significant issue.

Graham
 
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