Higher Amp Rating at lower voltage ?

I bought some of these.

SPDT ON/ON , stationary, two position, three solder lugs Face: 1.36" x .550"

0.5A @125VDC 3A @ 125VAC

Is the amp rating higher if used with a much lower DC voltage?

Like say 25 V dc.

Andy

Reply to
Andy
Loading thread data ...

** DC is very different to AC when it comes to switch or relay ratings.

That switch is probably good for 2A at 25VDC. Any more, and the contacts may break into a steady arc.

.... Phil

Reply to
Phil Allison

No.It's dominated by the damage done by arcing at turn-off. The AC rating i s higher because the arc turns off within 10msec (at 50Hz, or 8.333msec at

60Hz).

The energy dumped in the separating metal surfaces has to be low enough tha t the surface doesn't melt, pit and erode, and that's essentially determine d by the current flowing through the contact and not much influenced by the voltage driving that current (as long as the voltage is high enough to sus tain the arc, which isn't much, once it has started).

--
Bill Sloman, Sydney
Reply to
bill.sloman

Probably 1.5A or more at 28VDC, it should be in the data-sheet.

--
This email has not been checked by half-arsed antivirus software
Reply to
Jasen Betts

is higher because the arc turns off within 10msec (at 50Hz, or 8.333msec a t 60Hz).

hat the surface doesn't melt, pit and erode, and that's essentially determi ned by the current flowing through the contact and not much influenced by t he voltage driving that current (as long as the voltage is high enough to s ustain the arc, which isn't much, once it has started).

That makes sense.

Andy

Reply to
Andy

If the load is mostly resistive, the low voltage safe DC current rating will be 3A. If it's substantially inductive, an opening contact can arc and, worst case, melt the contacts or the switch.

--
John Larkin         Highland Technology, Inc 

lunatic fringe electronics
 Click to see the full signature
Reply to
John Larkin

Is this a case where putting a capacitor across the switch contacts will help? (when the contacts open the capacitor allows current to flow for long enough so that the contacts are to far apart to arc when the cap is charged)

--
I look forward to the day when a chicken can cross the road without having   
its motives questioned.
Reply to
David Eather

I had to use a magnifying glass, but switch has this on it.

3A AC .5A DC 125V

It looks pretty heavy duty.

Why is there 3 lugs? Seems like only 2 are needed.

Andy

Reply to
Andy

---------------------

** Judicious use of a film cap or C plus R will help with the max voltage that can be reliably broken.

A value of about 1uF is a good starting point, a R of about 1 ohm helps with high discharge currents when the same switch closes.

Not all circuit arrangements are happy with such a cap or RC in place.

** LOL

..... Phil

Reply to
Phil Allison

-------------------

** It helps when you want to switch a load between two sources of voltage OR the same source between two loads.

Plus it can do simple on-off as well.

.... Phil

Reply to
Phil Allison

We might encourage Andy to post on SEB. (Sci.electronics.basics) It's dead over there and his questions are basic.

George H.

Reply to
George Herold

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.