Switch lifetime at a capacitive load
Switch lifetime at a capacitive load
(OP)
The lifetime of a switch is usually 10,000 cycles at AC
line voltage. How does the lifetime changes if I use it to
switch a 12V circuit which has 1000 uF input filter
and much lower steady state current ?
line voltage. How does the lifetime changes if I use it to
switch a 12V circuit which has 1000 uF input filter
and much lower steady state current ?
<nbucska@pcperipherals DOT com> subj: eng-tips
read FAQ240-1032





RE: Switch lifetime at a capacitive load
RE: Switch lifetime at a capacitive load
RE: Switch lifetime at a capacitive load
The circuit has 1000 uF parallel to the input
i.e. at turn-on the current is limited only by
the wire and the battery's internal resistance.
<nbucska@pcperipherals DOT com> subj: eng-tips
read FAQ240-1032
RE: Switch lifetime at a capacitive load
specified for 60 amps if the parasitic resistances are
.2 ohm ? What is a reasonable safety margin ?
361 seems to be slightly too much !
<nbucska@pcperipherals DOT com> subj: eng-tips
read FAQ240-1032
RE: Switch lifetime at a capacitive load
The theory behind that was that the cap switching causes a slight amount of additional heating effect, so by reducing the current capacity rating of the contacts, you minimize the net effect that would have on their lifespan. If your contacts are already rated to switch far more than you are switching, then as itsmoked said, it probably doesn't matter.
"Our virtues and our failings are inseparable, like force and matter. When they separate, man is no more."
Nikola Tesla
RE: Switch lifetime at a capacitive load
One option is to add some series resistance (a few ohms) to the circuit so that the capacitor isn't charged 'instantly' by battery when the switch is closed. Also, re-examine the decision to use 1000uF - perhaps it should be less ?
The switch manufacturer should (in theory) be able to provide some technical data regarding the capabilities of the switch when faced with such capacitive loads.
Another thing to keep in mind is that the peak current would depend on the type of batteries used. If the user switches to NiCd battries (for example), then the peak current would be much more than with regular alkaline batteries.
RE: Switch lifetime at a capacitive load
RE: Switch lifetime at a capacitive load
http://myronzucker.com/docs/CAPACITALK%20105.pdf
"Our virtues and our failings are inseparable, like force and matter. When they separate, man is no more."
Nikola Tesla
RE: Switch lifetime at a capacitive load
Eg 115VAC 10A = 28VDC 10A resistive or 2A lamp load.