Relay Contact Life

[zimmerDN]

Hi

I want to estimate the relay contact life that is switch some 120VAC solenoids.

The manufacturer provides a graph listing expected operations VS switching current. That's quite easy to follow if you have one solenoid being switched by the contact.

Question #1
But how do you determine the switching current if the contact is wired to (2) solenoids in parallel they each have slightly different inrush ratings? Do you take the sum of the currents from each solenoid?


Question #2
Do they take into consideration of arc destruction when these relay life curves are created? Meaning if surge suppressor is NOT applied, that's the life you should expect?
There are multiple lines on the chart for resistive and inductive loads for AC and DC.

 

[itsmoked]

1) Sum them.

2) It is ALL about the arc. The arc is what causes the "electrical life" as compared to the "mechanical life". They do not consider arc mitigations. Keep in mind MOVs wear out.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[zimmerDN]

itsmoked,

Thanks for the reply. Can you help me understand what you mean?

Do you believe the curves (attached) that are published only suggest the mechanical life? Therefore any arcing will further reduce the life of the contact beyond what's stated on those curves?

Why do they publish multiple lines for different conditions then? The resistive loads have the longest life and AC 250V inductive load have the lowest life.


What I really want to know is if the published life expectancy expects the use of a surge suppressor.

 

[waross]

Given the reduction in both current capacity and number of operations for a 250 VAC inductive load versus a 250 VAC resistive load I suspect that arc suppressors are not considered.
But read the fine print on the manufacturer's data sheet.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[analogkid2digitalman]

Use an AC solid state relay (SSR)with zero crossing feature.

-AK2DM

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"It's the questions that drive us"
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