Relay & Timer Contacts

[junorebel]

What is a "race" or is it "rise" of a contact?

 

[jbartos]

Suggestion: It depends.
The contact race is between two different contacts, each part of a different relay. The one that closes or opens first or closes first logically counts. This is normally to be avoided since it is not easy to determine which contact will close first.
The contact rise may be viewed as an approaching movement in the energized condition of relay, contactor, etc.

 

[junorebel]

Thanks "jbartos" Reason why I ask is because I had to troubleshoot a Low Volatage Control Panel the other day and upon powering of the Relays, they would begin to chatter a lot. That is when someone told me that I had a race of contact.
Is this something anyone has ever experienced?

 

[jbartos]

Suggestion: Relay chatter may also come from the relay coil undervoltage and or from a poor design.
Relay contact race is rare. It would indicate a lack of experience in the switching logic engineering or design.

 

[PUMPDESIGNER]

jbartos,
You are good, very good, all that you said is true except ...
You live in a nice situation evidently.
I see horrible stuff all the time, beyond description bad.
Backfeeds, relay races, poor connections, erratic everything. I saw one panel recently sold to a GSA project, high security, cannot even go onto the site without much advance notice.
They asked me to look at their panel, not working since new about 1 year ago. Not one stinkin feature worked as specified, in fact, no worky at all except it did turn on the pump automatically. What do they do? They work stuff by hand, never go back and demand satisfaction from the builder.
There is more junk out there than we will ever know.
In fact, I bet all the new guys do not know how much about how to build with relays, they learned on ladder logic where the PLC prevents those problems.

PUMPDESIGNER

 

[jbartos]

Comment: There are excellent university textbooks dealing with switching logic; however, they are missing some vital practical aspects of switching, e.g. Reference:
Zvi Kohavi "Switching and Finite Automata Theory," 2nd Ed., McGraw-Hill, 1978, is missing important practical coverage of contact "make-before-break" and vice-versa.