16A 250V switch rated for 10000 ops at mains peak or zero cross?

[treez]

Hi,
The below switch says its rated for 10000 operations. But does that mean 10000 operations with the switching happening at the zero crossings, or 10000 ops with switching happening at mains peak?

I assume that the switching refers to when 16A flows at the instant of switch contact make?...ie not instances where in a 16A circuit, massive inrush of 70A (say) flows through the contacts at make time?

Also, the datasheet says it doesn’t refer to inductive switching for the 10000 ops…but in reality , all circuits will have stray inductance, and so we can safely say that the real rating will be nowhere near 10000 ops?

Do you agree that when this switch gets worn out...the contacts will stick together for some time instead of breaking immediately.?

16A switch: (0911 on pg 172)
**broken link removed**

 

[betwixt]

You will have to ask them. They are "snap action" which usually means they have a spring activated mechanism and that in turn usually means they close and release very rapidly. All switches wear out eventually, I would guess their figures are not based on someone pressing the button 10,000 times in a variety of load situations but by wear on the mechanism and contacts from a smaller number of operations or by an automated pressing process.

Brian.

 

[FvM]

all circuits will have stray inductance, and so we can safely say that the real rating will be nowhere near 10000 ops?

A pointless statement, I think. There's a reason why switch and contactor rating distinguishes between resistive and inductive load, although any circuit has some inductance. An inductive load has L/R circuit time constant which is at least in the contact opening time order of magnitude, e.g. 100 us to several ms. That's not the case for a mostly resistive load.

 

[treez]

Thanks, by "contact opening time" you are speaking of "contact bouncing time"?

I believe we would agree that an ideal world resistive circuit, with no inductance, would not suffer any contact sparking as the switch bounced at make or break...thus the ideal resistive circuit, would last a very long time, as its the inductive sparking at make or break which does all the damage to switch contacts?

 

[KlausST]

Hi,

Imagine just the energy stored in the inductance.
It creates the spark.
Low energy will cause low damage, high energy will cause high damage.

Klaus

 

[treez]

i agree its low energy, though cant it spark off oxidation in the contacts? Also, the damage is cumulative, and the contact chrome coating is microscopically thin.
Or would it be said that contact damage after xxx operations is due to the actual mechanical banging together of the contacts?...this is another low energy thing.
I always thought it was the inductive sparking (made worse by bouncing), which damages contacts?

 

[FvM]

There's typically no bouncing during contact opening.

If the device has trustworthy specification, as I expect for a Bulgin product, and you don't have a dedicated inductive load, why not believe the spec? You didn't yet tell what the actual load is.

 

[Easy peasy]

all AC switches arc - obviously more for higher currents and higher L in series - if the contacts open quick enough ( quality AC switch ) then as soon as the current drops to zero, ( it does this 100/120 times per sec ) then that's it - open ckt - switch off ... where there is poor arc suppression - or if the plasma is allowed to exist near contacts that are too close together - you may get re-strike - this is the difference between a cheap AC switch and a good one ....