I have a switch marked as having a max current of 2A at 240Vac, and 6A at 125Vac.
What would its max current rating be at 12Vdc?
\$\begingroup\$
\$\endgroup\$
Add a comment
|
3 Answers
\$\begingroup\$
\$\endgroup\$
1
Technically, it is impossible to tell: switch manufacturers have to deal with the subtleties of arcing when designing circuits, and AC behavior is different than DC behavior. Arcs will be extinguished much more easily with AC (since voltage passes through zero) than with DC.
It's odd that the rating drops so much at 240VAC from the 6A rating at 125VAC. If the limiting factor were thermal behavior, I would expect the current rating would be the same. So I'm guessing they're probably using a particular test condition, like opening the switch with maximum rated current, assuming there's bouncing in the switch which may cause an arc.
Ask the manufacturer....
-
\$\begingroup\$ I cannot believe this only got one upvote. \$\endgroup\$– KortukCommented Jun 6, 2010 at 19:07
\$\begingroup\$
\$\endgroup\$
The general rule of thumb for switches with 125VAC or 240VAC ratings is that the switch will operate satisfactory up to 30VDC at the highest rating listed on the switch. IIRC I read this rule at the carlingtech.com site.
\$\begingroup\$
\$\endgroup\$
3
Impossible to say, but it would be OK for 6A. You could measure the resistance through the contacts and estimate it from that.
answered Apr 24, 2010 at 22:23
-
\$\begingroup\$ Would an answer depend on what temperature the metal might reach at that current, and its corresponding resistance? \$\endgroup\$– CHCommented Apr 24, 2010 at 22:26
-
\$\begingroup\$ OK for 6A: not true; it's rated for AC, the OP is using it at DC. \$\endgroup\$– Jason SCommented Apr 25, 2010 at 0:57
-
\$\begingroup\$ See jluciani's answer. It's the correct rating in the absence of any other data. The calculation would depend on the contact resistance, the mass of the metal, and so on, which would determine the temperature. \$\endgroup\$ Commented Apr 25, 2010 at 10:52